[Map Reproduction in the Field]
[From the U.S. Government Publishing Office, www.gpo.gov]
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WAR DEPARTMENT TECHNICAL MANUAL
NON-CIRCULATING
MAP
REPRODUCTION
IN THE FIELD
AAR DEPARTMENT • MAY 1946
NTSU LIBRARY
WAR D E P A R T M E N T T E C H NIC A L M A N U A L
TM 5-245
This manual supersedes TM 5-245, Topography and Surveying Map Reproduction, April 1942
MAP
REPRODUCTION IN THE FIELD
WAR DEPARTMENT • M A Y i 9 46
United States Government Printing Office W ash ing ton: 1946
WAR DEPARTMENT
Washington 25, D. C., 1 May 1946
TM 5-245, Map Reproduction in the Field, is published for the information and guidance of all concerned.
[AG 300.7 (4 Dec 45)]
&
By order of the Secretary of War:
Official :
EDWARD F. WITSEL1
Major General
The Adjutant General
DWIGHT D. EISENHOWER Chief of Staff
Distribution :
AAF (io) ; AGE (io) ; ASF (2) ; T (5) ; T (Eng) (10) ; Arm & Sv Bd (1) except Eng Bd (50); S Div ASF (1) ; Tech Sv (2) except OCE (75) ; ASF Dep (2) ; Dep 5 (2) ; Gen & Sp Sv Sch (2) except Eng Sch (100) ; ROTC (2) ; AGF Tng C (2) ; A (5) ; A (Eng Sec) (5) ; CHQ (10) ; CHQ (Eng Sec) (3) ; D (2) ; B (2) ; R (2) ; S Bn 5 (1) ; T/O & E 1-752(3); 1-760-1(3); 5-47(i); 5-55(io); 5-56(5); 5-57(io); 5-59(1); 5-167(10); 5-186(5); 5-188(3); 5-267(1); 5-400(10); 5-447(3): 5-592(i).
Refer to FM 21—6 for explanation of distribution formula.
ii
CONTENTS
CHAPTER I. INTRODUCTION Paragraphs Page
Section I. Purpose and scope ............................. 1-2 1
II. Theory of photolithographic processes .............. 3-8 1
CHAPTER 2. PLANNING Section I. Map characteristics .................................. 9-11 9
II. Production planning .............................. 12-16 10
CHAPTER 3. MAP COPY PREPARATION Section I. General ............................................. 17-20 16
II. Drafting ......................................... 21-23 20
III. Copy corrections ................................ 24-27 21
IV. Color separation ................................. 28-29 22
CHAPTER 4. PROCESS PHOTOGRAPHY Section I. Equipment and materials ............................. 30-44 24
II. Negative making .................................. 45—56 46
CHAPTER 5. NEGATIVE CORRECTIONS AND LAY-OUTS Section I. Negative corrections ............................. 57-62 59
II. Lay-out ......................................... 63-68 63
CHAPTER 6. PLATE GRAINING Section I. Equipment............................................ 69-70 67
II. Graining procedure ............................... 71-73 69
CHAPTER 7. PLATE PROCESSING Section I. Equipment and materials ............................. 74-76 72
II. Plate making ..................................... 77-89 74
CHAPTER 8. OFFSET PRINTING Section I. Equipment and materials ............................. 90-91 88
II. Press operation (preparatory) ................... 92-100 93
III. Press operation (running) ..................... 101-105 111
CHAPTER 9. MISCELLANEOUS MAP-REPRODUCTION PROCESSES .. 106-113 121
CHAPTER 10. FIELD EXPEDIENTS ............................... 114-119 137
CHAPTER II. MAP STORAGE AND DISTRIBUTION ................... 120-122 140
APPENDIX I. SUPPLEMENTAL TABLES 142
II. GLOSSARY ...................................................... 147
III. REFERENCES .................................................... 154
INDEX ...................................................................... 157
iii
SAFETY PRECAUTIONS
SOME OF THE CHEMICALS USED IN MAP REPRODUCTION ARE SKIN IRRITANTS AND OTHERS MAY CAUSE MORE SERIOUS INJURIES. ALL CHEMICALS MUST BE RECARDED AS POISONS AND ACCORDINGLY HANDLED WITH CAUTION.
I. Acids
Concentrated acids can cause severe skin burns. If any strong acid comes in contact with skin, wash immediately with water. Neutralize with bicarbonate of soda solution or other weak alkali.
2. Alkalis
Concentrated alkalis can burn and destroy tissue. Wash off immediately with water and neu-tialize with weak acid (diluted acetic or hydrochloric acid) followed by further washing.
3. Vapors
Some chemical release poisonous vapors, and their handling must be conducted under adequate ventilation.
a. \ olatile Liquids. Carbon tetrachloride, benzol, formaldehyde, wood alcohol, ammonium hydroxide and leaded gasoline are all toxic.
b. Chemical Reactions. Nitric acid in contact with wood or organic material liberates deadly vapors. Cyanides in contact with acid release deadly gases.
4. Chromates
(. bromic poisoning can be contracted from all forms of chromates and bichromates including sensitizer, plate etch, and fountain solutions. Cleanliness, avoiding skin contact, and washing' immediately after chromates touch skin are essential to prevent dermatitis. Chapped skins are more sensitive to poisoning, and skin creams should be used in cold and dry climates. (Poisoning results in severe skin rash and ulcerations.)
5. Inflammables
Gasoline, benzol, benzine, collodion, alcohol are all dangerously inflammable. Smoking, or use of electrical heating equipment in their vicinity, must be prohibited. All gasoline lines to heating units must be periodically inspected for leaks.
6. Radiations
Arc lamps and mercury-vapor lamps radiate ultraviolet light that can cause severe eye burns. Never look directly into such lights, or if examination is momentarily required use safety glasses or a blackened negative.
7. Electrical Shock
Shorted equipment can result in severe shock in handling or on touching vehicle, especially when standing on damp ground. All equipment and vehicles should be grounded and checked periodically for faulty insulation.
8. Moving Machinery
Although guards are provided wherever possible, careless use of ink knives, tools, sponges or rags, or dangling articles of clothing can result in serious damage to equipment and injury to personnel.
iv
this manual supersedes 7 .V/-5245, Topography and Surveying Map Reproduction, April 1042.
CHAPTER 1
INTRODUCTION
Section I. PURPOSE AND SCOPE
I. Purpose
This manual is intended as—
a. Text for training in map-reproduction methods used in the field.
b. Working guide to detailed procedure followed in reproducing maps with mobile printing units.
c. Background material on map-reproduction theory so operators can devise expedients and adapt
the procedure to available equipment and materials.
2. Scope
I his manual describes all methods used in reproducing maps and photomosaics in the field. It gives general instructions on how to operate the various types of equipment now in use. Specific information regarding equipment adjustments is given in instruction manuals supplied with the equipment.
Section II. THEORY OF PHOTOLITHOGRAPHIC PROCESSES
3. Map-reproduction Methods
Maps and aerial photographs can be duplicated by photography or by printing. Photographic methods reproduce more accurately and furnish more detail, but production is slow and is usually limited to a single color. The printing methods depend on the transfer of ink from the printing form to the sheet of paper. Although printing methods may not keep all the fine detail, they can reproduce large quantities of single-or multiple-colored maps at comparatively high speeds. All printing methods, including letterpress (photoengravings or line cuts), rotogravure, stencil duplicating (including silk screen), collotype, gelatin and fluid duplicators, and lithography can be used for map reproduction. The photolithographic process combines the advantages of photographic detail with printing speed, and, because of its versatility and simplicity, is used for most field map reproduction.
4. Photography
Photography uses the action of light to produce images on a sensitized surface. These images may become directly visible on exposure to light, or thev may be latent and invisible, requiring chemical treatment to develop them so they can be seen. Photographic pictures are either composed of minute particles of metallic silver, stained by dyes, or tanned into organic materials.
a. Camera. I lie camera is the basic tool used in reproducing by photography. In its simplest form, it is a box from which all light is excluded except that passing through the glass lens. Light from the object being photographed is projected by the lens as an inverted image on the back wall of the camera. If a light-sensitive material is placed on the back wall and exposed, it can be developed as a negative. I he negative is then used as a stencil to permit more or less light to pass through to the photographic printing paper. \\ hen the paper is developed, it is a reproduction of the original subject.
b. Negatives. Photographic negatives are available in several forms and in a wide range of sensitivity to light intensity and color. They consist essentially of a transparent glass or plastic base coated with a thin layer of a gelatin emulsion in which the light-sensitive salts are uniformly suspended. When the light-sensitive salts are exposed to light and then developed, they are reduced to black-appearing particles of metallic silver. The amount of silver precipitated is directly proportional to the relative intensity of the light reflected from the object being photographed, d he remaining unexposed silver salts are then removed by dissolving them with a fixing solution so only the negative image, composed of small grains of metallic silver, remain in the gelatin emulsion. I he negatives used in map reproduction are broadly classified as continuous-tone and photo
mechanical. Both types are similar in general composition and properties, and vary only in relative sensitivity and grain size.
(i) Continuous-tone negatives. Continuous-tone negatives have a continuous range of image density from the high lights (brighter portions of the subject) to the shadows. (See fig I.) Their contrast range is approximately that of the subject being photographed. The grain size of the negative image generally varies directly with the light sensitivity of the emulsion. ‘
cause these processes transfer a solid color of ink from the printing form to the paper, shades of color can be obtained only by printing minute dots of ink of varying sizes so closely spaced as to appear to be a continuous-tone image.
5. Lithography
Lithography is a printing process based on the principle that water and grease repel each other. The printing design is drawn or deposited as a greased image on the surface of a lithographic plate.
CONTINUOUS TONE
LINE
Figure 1. Continuous-tone, line, halftone prints.
HALFTONE
(2) Photomechanical negatives. Photomechanical negatives have high-contrast and fine-grained emulsions. High contrast is required to produce printing plates that have sharply defined printing areas. Photomechanical negatives are further classified as line and halftone negatives. Line negatives are made by exposing the negative from copy composed of opaque black markings on a white background. Halftone negatives are negatives in which the continuous tone of the copy has been broken up into a pattern of fine dots formed by a halftone screen mounted on the camera in front of the negative. The size of each dot varies with the brightness of the corresponding area of the copy. Halftone negatives are required in reproducing continuous-tone subjects by letterpress or photolithographic printing processes. Be-
Moisture is then applied to the plate where it is repelled by the greased design but dampens the remaining areas. A grease ink is next applied to the plate with an ink roller. The greased image attracts the ink from the roller while the dampened areas repel the ink. The ink received by the plate is then printed on paper either by direct contact or by the first being deposited on a rubber blanket which then transfers the ink to the paper. The process was named “lithography,” the Greek word for “writing with stone,” by Alois Senefelder, who discovered the method, originally using a limestone slab on which to sketch his subjects. Limestone slabs are still in limited use for map and commercial work. They are now largely superseded by metal plates treated to have similar lithographic properties. A metal plate
2
is more easily handled in preparatory stages and in the printing operation where it can be strapped around the cylinder of the high-speed offset press.
6. Photolithography
Photolithography covers all photographic methods used in preparing lithographic printing plates. It includes the albumen, reversal, and deep-etch processes as well as several less common methods using asphaltum, gelatin, or other colloids. All these processes require exposure to light to tan (make insoluble in water) specific areas of the sensitized coating-on the lithographic plate.
a. Albumen Process, (i) General. The albumen process is the simplest and most extensively used photolithographic process. (See fig 2.) The sensitized plate is first exposed to light passing through a line or halftone negative. The resulting exposed portions of the bichromate albumen coating on the plate become insoluble in water and form the base for the printing image. Since the albumen coating is not ink-receptive, it is greased and made ink-receptive by applying a thin coating of developing ink to its surface. The plate is then immersed in water which dissolves the unexposed areas of the albumen coating leaving the exposed insoluble areas adhering to the plate and retaining their greasy developing-ink
covering. The plate is next treated to make the nonprinting areas grease-repellent, after which it is ready for printing.
(2) Sensitizer. The albumen sensitizer is a solution of egg albumen (white of the egg) and ammonium bichromate. It contains a small percentage of ammonia water as a stabilizer. The sensitizer is applied to the prepared lithographic plate in a coating machine (whirler) that spreads the solution and dries it in a thin uniform layer. Exposure to light breaks down the ammonium bichromate salt, liberating active chemical agents and tanning the albumen emulsion. The albumen image remains underneath, becoming the foundation of the printing areas of the plate. ’Since the emulsion is hygroscopic and may absorb enough water to reduce its ink-attracting properties, it must be as thin as possible, fully exposed, and used with as little moisture as will permit satisfactory printing. Improved sensitizers using casein (prepared from milk) or the polyvinyl alcohols have been developed, but are not yet satisfactory substitutes for albumen in field map reproduction.
b. Reversal Process. In the reversal process, the grease-receptive image is deposited directly on the metal of the plate. This is accomplished by exposing through a positive instead of a negative in mak-
” T ~ I jsripper edgeT-paper_edgLJ F ' ' T”’1
US
k.P. NEGATIVE TAPED TO
MASKING PAPER
1. GRAINED LITHO PLATE
3. PLATE SENSITIZED AND EXPOSED THROUGH NEGATIVE
4. DEVELOPING INK APPLIED TO PLATE
2. NEGATIVE PREPARED FOR EXPOSURE TO PLATE
5. PLATE PARTLY DEVELOPED
Figure 2. Albumen plate processing.
6. PLATE COMPLETELY DEVELOPED AND FINISHED READY FOR PRESS
3
ing the plate so the areas surrounding the printing design are tanned to form a protective stencil. 'I'he printing-design areas are then developed away to the metal, and a grease-receptive printing base is applied to the entire plate. The surrounding tanned coating is then dissolved away with a weak acid or alkaline solution, leaving the greased printing design on the cleared metal plate. A final chemical treatment (etching and gumming) makes the nonprinting areas of the plate water-receptive and grease-repellent.
by the plate is proportional to the degree of tanning of the bichromated geltain coating. Exposure is made through a continuous-tone negative. The plate must be dampened and can be run on offset presses if ink and water are properly adjusted. Recent developments include the chemical tanning of photographic negative emulsions, permitting the negative exposed in the camera to be used directly on the press. All gelatin processes are still too undependable for field use.
(2) Asphaltum coating. Thin asphaltum coatings
—i TTnl?
pncmvA OPAQUE {TRANSPARENT LIGHT-HARDENED BARE METAL
COATING-----AREA—* 1 —AREA L—7 STENCIL PLATE
—X::— ,J***!.. ..m._ _d m 4 r-77—■
PRESS PLATE | PRESS PLATE J PRESS PLATE
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BARE METAL r--PLATE
INK BASE
[Tress
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4. DEEP-ETCHED
5. INK BASE APPLIED
Digure 5. Deep-etch plate processing.
6. STENCIL REMOVED
c. Deep-etch Process. Deep-etch plates are similarly processed, with an additional etching operation following development. (See fig. 3.) The etching dissolves away the top surface of the metal, leaving the grease-receptive base slightly recessed below the surface to accept more ink and permit longer press runs.
d. Other Processes. Several other commercial photolithographic processes are of general interest. While not normally used in map reproduction, further improvements or field expediency may necessitate applying them to mapping procedure.
(1) Collotype process. The collotype or photogelatin process is a full-tone or continuous-tone printing method in which the amount of ink accepted
are sometimes used as light-sensitive coatings on lithographic plates. While they require at least double the exposure needed for albumen plates and must be developed in benzol or gasoline, they are not hygroscopic and form an ink-receptive coating extending down to the surface of the metal.
(3) Bimetal plates. Bimetal plates use a thin electro deposit of grease-attracting metal for the printing areas, and a water-receptive metal, such as stainless steel, for the grease-repellent areas. Plate processing is similar to making a deep-etch plate, except that a negative is used instead of a positive, and the copper deposit in the nonprinting areas is removed by the etch.
4
7. Lithographic Printing
Lithographic plates can be used for printing directly on sheets of paper. Better results are obtained, however, by the indirect or offset method in which the plate prints on a rubber blanket that in turn prints or “offsets” the inked image onto the paper. (See fig. 4.) The offset method lengthens the life of the plate, reduces the transfer of water from the plate to the paper, and permits printing on a variety of surfaces because of the resiliency of the rubber blanket.
tion for each color, a general knowledge of color theory is helpful in understanding its characteristics.
a. Theory of Color, (i) Light and color are sensations received by the nerve cells in the retina of the eye in response to external radiating or reflecting sources of energy. The optics of the eye are similar to a camera, the corona corresponding to the lens and the retina to the ground glass or the sensitized negative emulsion. The nerve cells in the retina are two types, rods and cones. The rods are stimulated by blue light but are color-blind to the
INK-FOUNTAIN
ROLLER
INK FOUNTAIN
RIDER
ROLLERS
PLATE CYLINDER
PRESS FEED
BLANKET CYLINDER
VIBRATING
ROLLERS -
INK FORM
ROLLERS -
DAMPENER DUCTOR ROLLER
PRESS DELIVERY
DELIVERY PILE
INK-DUCTOR ROLLER
INTERMEDIATE ROLLERS
INKDISTRIBUTION
SYSTEM '
WATER-DISTRIBUTION SYSTEM
BRASS DAMPENER-VIBRATOR ROLLER DAMPENER-FORM ROLLERS
WATER-FOUNTAIN ROLLER
- WATER FOUNTAIN
INK
DRUM
Figure 4. Offset press.
J
DELIVERY CHAIN '
IMPRESSION CYLINDER
SKELETON CYLINDER
8. Color in Maps
Color adds to the scope of maps, permitting them to carry additional information without confusing detail. Color is similarly desirable for photomaps, instruction manuals, charts, and posters. Since color reproduction requires an additional printing opera-
red and green to which the cones respond. Since the rods are far more 'sensitive than the cones, they record light at much lower levels of intensity. As a result, the color of an object seems to change with diminishing light intensity until everything appears to be bluish gray. This property is important in planning maps to be used at night.
5
(2) When the intensities of all colors in the spectrum to which the eye responds are uniformly balanced, the resulting sensation is called “white light.” If some of the colors are cut out, the nerve cells in the eye do not respond uniformly and the sensation is color. The relative stimulation of the rods and cones to the intensities of the three primary color sensations (red, green, and blue) radiated or reflected from the object determines the individual’s interpretation of the color. Accordingly, all colors are mixtures of the three primary colors. When no light is received from an object, the color sensation is black.
( 3) Since color is not a physical property but is a mental reaction to an object, it is subject to the variations of the observer’s nervous system. The nature and intensity of the light, the degree of fatigue, the surrounding colors, and the existence of partial or complete color-blindness influence an individual’s reaction and his judgment of color.
either by the additive or subtractive methods. When colors of light are added together, red, green, and blue are the primaries. All other colors are obtained by combining these primaries. The addition of red to green light, for example, produces yellow light, and combining all three primary colors (or any one and its complementary color) in full intensity results in white light. (See fig. 6.) In the subtractive combination of light, such as obtained when light is passed through a series of different colored filters, the resulting color transmitted is that not absorbed by any of the filters. For example, when white light is passed through a combination of blue and yellow filters, the remaining light transmitted is green. Combining the three primary subtractive colors (blue, yellow, and red), or one primary and its complementary, blocks out all light resulting in black. In reproducing colored originals, both additive and subtractive combinations influenced each stage of the process.
II 1 "COSMIC RAYS u 1 GAMMA RAYS X-RAYS 1 1 1 ULTRA VIOLET jVISIBL^ INFRARED ' 1 I » 11 "T RADIO WAVES 1 1 1 1 1 1 1
.001 .01 .1 1 10 102 103 • io4 105 106 107 108 109 1010 10n 1012 1013 A°
I I
J \
4 VISIBLE REGION OF ELECTROMAGNETIC RADIATION SPECTRUM ▼ --1---------j-------1--------------1---1----1-------------------------1-------
RELATIVE VISIBILITY 3 f
ULTRAVIOLET
-
1
I VIOLET 1
I
1___________________
\
\ BLUE --------------------
GREEN cn x
_ m x OZ A -n co /
m m /
YELLOW ORANGE
/
/
I t | RED
I
INFRARED
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(4) Although color is a sensation, the energy or light waves that stimulate it are physical properties that can be controlled and measured. Instruments such as the spectrometer and spectrophotometer can unravel a beam of light and spread it out as a band so its wave lengths can be measured and identified. (See fig. 5.) Similarly, by measuring the wave lengths of light reflected from colors on the map copy, or by separating the wave lengths with filters, color can be accurately controlled or classified.
(5) Colors can be combined to form new colors
b. Color Comparison. The original colors in the copy are altered by the kind of illumination used. (See fig. 7.) Various forms of lighting (such as carbon arcs, incandescent lamps, or daylight) are composed of differing proportions of colored lights. When these are used to illuminate the copy, each type of light combines differently with pigments in the copy, resulting in apparent differences in their coloring. The eye also tends to blend complemen-taries of adjacent colors with the particular color being observed. To avoid this blending, colors are
6
4,000A° 5,000A° 6,000A° 7,000A° 8,000A°
Figure 5. Spectrum.
.x^TYELLOW 1 CYAN jBk wu*^w ‘
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__________,_______ , 2I I I , II 2,000 3,000 4,000_5,000_6,000 7,000 8,000
LIGHT SPECTRUM (ANGSTROM UNITS)
ligurc p. Special distribution of light sources.
8
CHAPTER 2
PLANNING
Section I. MAP CHARACTERISTICS
9. Functional Purpose
A map is essentially a sheet of symbols intended to convey tactical information quickly and accurately. It must be simple in design, legible, and not confused by unnecessary references or detail. Symbols, drafting, type faces and sizes, and colors must be selected to allow rapid observation. Excessive unimportant detail and masses of color may appeal to the artist or map collector but they have no place in military mapping.
Approach charts (no scale).
High and low obliques and landfalls depicting appearance of target area at specified distances (5 and 15 miles).
Target.....1 :
b. Photomaps.
5.000 Bombing operations.
Tactical . . . . 1 : 50,000
Battle........1: 25,000
Large scale. . 1 : 10,000
Large scale. . 1: 5,000
10. Types of Maps
Map reproduction companies must reproduce a wide variety of specialized maps ranging from those large enough for global or theater planning to small specific functional maps for a single movement or operation. To conform with reproduction procedure, these maps are grouped in two classes: cartographic or line maps; and photomosaic, or halftone maps. Typical maps are listed below:
a. Cartographic Maps.
Ground forces:
Strategic . . 1: 1,000,000 Regional planning.
Strategic . . . , . 1: 250,000 Operational planning.
Strategic . .. . . 1: 125,000 Operational planning.
Tactical . 1: 50,000 Disposition and m 0 v e m ent of forces.
Battle . 1 : 25,000 For immediate operation and artillery fire control.
Large scale . . 1: 10,000 ) Town plans, tar-
Large scale . Air forces: . 1 : 5,000 f get areas.
Global.......i: 5,000,000 Regional planning.
Air charts . . . . 1 : 250,000 Flight navigation.
I I. Map Sizes
a. Map size is limited by the sheet size and maximum printing area of the presses. The standard presses normally issued map reproduction companies are as follows:
Press Sheet Size (inches) Maximum printing area (inches)
'Multilith 2066 Harris LTE ATF-Webendorfer . 19x20 20x22% 22x29 17x19% 19%x22% 22x28
b. Paper stock is supplied in sizes to fit the maximum capacity of the presses. To maintain standard map sizes and permit overprinting in register when required, sheets are normally used without trimming or cutting.
c. The design size of the map is determined by its scale and coverage, the map projection used, and the latitude being mapped. A 15-minute quadrangle, for example, increases in size as it approaches the equator while a 10,000-yard grid remains unchanged. (See fig. 8.) The remaining printing area is used for references, marginal data, scale, symbols, glossary, and other usable map data.
9
3.77”
80’ N (NE SPITZBERGEN)
60’ N (SEWARD, ALASKA) (OSLO, NORWAY)
40’ N (PHILADELPHIA)
20’ N (SANTIAGO DE CUBA)
03 (EQUATOR)
6o ?
CM
14.40" 3.87"
10.94" I co
________ 14.40"
11.03"
16-78" r—_,
« §
CM ___________ 14.40" 16.84"
20.58"
o
_____________ 14.40"
20.62"
21.91"
14.40"
21.91"
1:50,000 1:25,000
15 MINUTE QUADRANGLES
10,000 YD GRIDS
Figure 8. Map-size change with latitude.
Section II. PRODUCTION PLANNING
12. General
Administrative procedure in map reproduction units is essentially the same as in any other Army organization doing work demanding special skills. All-around training in all phases of map preparation and reproduction is necessary for coordinating the organization, but maximum quality and efficiencv
. d
ADMINISTRATION
| HQ & LAB |
_____F~~--------r I , MAP LAYOUT |----CAMERA ]■
'i ; td_______________________
PLATE PROCESS PRESS |
■♦I PHOTOGRAPHIC |~
j PLATE GRAINER |»
STORAGE & DISTRIBUTION |»
Figure 9. Organization chart.
result only from specialization. The organization of the mobile map reproduction company is shown in figure 9.
13. Classification and Records
a. When map copy is sent for reproduction, instructions as to size and scale of the finished map, number of colors, length of run, type of stock, classification, and required delivery date are included. Based on this information, the administrative officer determines whether the job can be handled in the form submitted, whether all necessary information and copy have been furnished, and whether size or other limitations of the equipment require obtaining approval to modify the instructions. The job is then classified and assigned a priority and sequence number. Instructions on operations and routing are entered on a routing form prepared in duplicate.
10
(See fig. io.) One copy of the form accompanies the map copy, and the other is kept in the files to check scheduling and progress. When the copy is small or folder, the scheduling form is prepared on a standard file-size envelope into which the copy, notes, and the prepared negatives or positives are later inserted for filing. Where possible, large copy is routed in protective envelopes or containers with the workorder sheet attached. It is generally advisable to put complete handling instructions on the routed copy to assure coordination of the job and minimize errors in passing on information.
b. The administrative office should have a large wall-mounted scheduling board, listing job progress, and promised and actual delivery dates. The most convenient board has a grid of wire hooks on which to hang punched cards of various colors indicating the classification and priority of the job. A blackboard prepared with painted titles and outlines to show scheduled time ahead and availability of presses, paper, inks, and plates in stock is also helpful in making quick time estimates. (See fig. ii.)
Unit
Quantity
3/ock
Rod
B/ue
Yal/oou
Extend?
Bromo
C>/Sp>O.si t/on
r
o. I
/ /
I Prepare, : . / /
/ / /
y' f SSPAKAT/Ar/ +_______y
5-- g~s.---W
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tracing paper or matte-acetate film OVERLAY
Figure 14. Protective overlay -for copy.
A<_^ SELF-ADHESIVE TAPE
STRING \
ZZZZZZZZZZ1ZZZZZZZZ J- .»^» nv-r-i
— ' y - - x - v— - , SECTION A-A
UNDERSIDE OF RULE
A*-J
TRIANGLES WITH ROUNDED SUPPORTING POINTS OR
PADS
ARM BOARD
Aids for protecting copy.
19
Section II. DRAFTING
21. Metal-mounted Drawing Paper
a. General. Drawing paper has poor dimensional stability when subjected to humidity variations, but is satisfactory for single-color map drawings if accuracy in size and proportion are not too important. A more stable drawing material is required to obtain good register in multicolor maps. Drawing paper securely mounted on metal or pressed fiberboard has dimensional stability and is used extensively in preparing blue-line color separation drawings. Regrained zinc or aluminum press plates can be used as a mounting base, but heavier .030-to .040-inch aluminum plates are preferred. Pressed fiberboard is not as good as metal but has low differential shrinkage, retaining accurate proportions that permits correcting size variations in the camera.
b. Mounting Procedure, (i) Mounting of all drawing materials requires a thoroughly clean and preferably a grained or roughened surface to bond well with the cement. To clean metal plates, remove all grease from both surfaces either by immersing in a 5 percent caustic soda or trisodium phosphate solution kept in a tray or tank (use rubber gloves in handling) or by graining in a plate-graining machine, followed by washing and drying. Clean the surface of pressed fiberboard by sanding with a medium-grade sandpaper or garnet paper.
(2) Place base material on a clean flat table and liberally apply mounting cement (either the cement supplied or a good grade of casein cement) to base with flat brush (3 or 4 inches wide).
(3) Immediately place drawing paper, cut slightly larger than base material, on base and cover with clean piece of protective paper.
(4) Using hand roller, roll drawing paper into contact with base. Roll from center outward to remove excess cement, and follow with straight strokes in both directions.
(5) Turn over base material (together with its protective paper covering) and mount another sheet of drawing paper on reverse side.
(6) Stack the prepared drawing paper, placing a large piece of blotting paper or several pieces of protective white paper between each mounted sheet.
(7) When enough mounted sheets are prepared and stacked, place metal or wood plate on stack, weigh down, and let stack dry for at least 8 hours
(preferably 1 or 2 days) or until base material is thoroughly bonded to paper.
(8) Remove mounted sheets from pile and dry thoroughly to prevent mildew, by spreading on shelves or stacking loosely. Trim excess paper to edges of base material.
22. Sprayed Lacquer Plates
a. General. White-lacquer plates prepared on a heavy (.040-inch) aluminum plate are also used for accurate drafting. By using metal styluses (strip silver, silver solder, or brass leads) to draw on the plates, a uniform width of line is maintained over the entire drawing. Lacquer base also accepts pencil, india ink, and other markings, and permits several erasures if necessary.
b. Preparation. (i) Clean aluminum plate with mild caustic soda or trisodium phosphate solution, or grain it.. This removes all grease and produces a slightly matte surface.
(2) Wash and dry plate thoroughly, avoiding hand contact in all operations.
(3) Spray base coat of white lacquer uniformly over entire surface, let set, and spray second coat. A third coat is sometimes applied for added resistance to erasures.
Note. Spraying equipment and supplies are not issued. Use paint-spray outfit and hard-drying white rubbing lacquer with thinner. Make trial coatings to learn technique for applying lacquer.
(4) After lacquer dries, rub down surface with a pad, using light paste of pumice powder. This produces a fine matte finish and removes greasy surface so plate accepts ink, pencil, and metal stylus marks satisfactorily.
23. Bromide Prints
a. General. Ink drawings can be prepared to agree with photographic detail by drafting directly on the photographic print. The silver image is then dissolved, leaving the inked drawing on the cleared photographic paper. This process is used for making line engravings from photographs, or for redrafting line sketches, symbols, or insignia that are poorly drawn or printed.
b. Procedure, (i) Make an enlargement (two to five times scale) on a negative.
20
(2) Contact print negative or project on photographic paper.
(3) Develop print with just enough density to see detail. Then fix, wash, and dry.
(4) Draw detail on print with waterproof india ink, and dry thoroughly.
(5) To remove silver image, immerse print in tray containing concentrated Farmer’s reducer (par. 56/', thoroughly wash, and dry. Handle carefully when wet, because inked image is easily removed by touching or rubbing. To remove errors in inking, wipe with damp tuft of cotton and then dry. Do not erase.
Section III. COPY CORRECTIONS
24. Correcting Injuries to Copy
a. Major Injuries. If detail is obliterated, stick-ups separated or copy distorted due to wetting, refer immediately to the originating organization. Do not try to correct or reassemble.
b. Minor Injuries. Minor injuries such as tears, scratches, stains, folds, and creases are corrected during reproduction.
(1) To mend tears, paste or join on back, using rubber cement or self-adhesive tape. Do not apply tape or patches to face of copy because they photograph differently and show edges on negative. Do not use gummed tape or water-soluble pastes in applying patches, because they distort copy unless mounted on metal or fiberboard.
(2) For minor scratches, chipping of ink, or gray lines or lettering, make corrections on negative for all but the simplest jobs.
(3) Do not remove grease and oil stains from copy. Solvents may spread grease, cause inked impressions to bleed, or loosen stick-ups or copy from base (yellowish stains can be removed photographically using orthochromatic negatives with a yellow K2 filter). If stains reproduce, retouch on negative.
(4) Although creases and wrinkles are usually minimized by proper camera technique, better results are obtained by mounting the copy on a metal or fiberboard base. Copy must not be rolled, and if received in this condition must be flattened carefully to avoid creases or surface cracks.
25. Masking
a. White Masks. White paper masks around map borders, on areas where the work is to be
deleted, and on large blank areas of copy that is spotted or dirty reduce the opaquing required on the negative.
b. Black Masks. Similarly, black paper masks (same paper as inserted between film negatives) produce clear areas on negatives for stripping in line or halftone films. It is also used as backing for thin copy printed on both sides to prevent detail on the back from showing through and recording on the negative.
26. Attaching Stick-ups
Rubber cement is the best adhesive for attaching stick-ups. It must have the proper consistency to adhere to the paper surface without penetrating into and staining the paper. Type-impression stick-ups on thin tissue or rice paper are usually attached to blue-line drawings with a gum-arabic solution, prepared with a preservative to prevent mold. (See par. 871/.)
27. Register and Corner Marks
All copy must have register, corner, trim, and other reference marks for help in printing, cutting, folding, and for color register. These marks generally are fine black lines drawn as shown in figure 16. Since much copy is received without reference marks, an expedient method is to prepare printed copies of reference marks, color-control scales, and other standard data or credit lines. Since many maps are not true rectangles (see 15-minute quadrangles in fig. 8) and some are bordered with curved lines, carefully locate corner and center marks because they are used by the press operator in squaring the work with the sheet.
21
CENTER MARKS
I I
CORNER MARKS - -
I I I
CUT OR FOLD TICKS
BLACK BLUE RED GREEN BROWN YELLOW
COLOR BLOCKS
GRAY SCALE
1,000 2,000 3,000 4,000 5,000 6,000
0 | । » । । i *i i i i | i*i i i i i i11 i |' i i H i i i i *i । i i r ।1
1 2 3
(ONE COLOR ONLY)
ADJOINING SHEETS
1------------r-----------1------------!— KM
2 3 4 5
SCALE 1:25,000
Figure 16. Reference marks.
Section IV. COLOR SEPARATION
28. Separations on Matte Acetate
Color-separation positives or negatives can be drawn directly from the map on matte acetate or vinylite sheeting.
a. Procedure for Positives, (i) Clean sheeting with one or more applications of carbon tetrachloride until all grease and dirt are removed.
(2) Securely attach sheeting over copy with strips of self-adhesive tape.
(3) Draw center and corner marks with india or cellophane ink. Make sure marks accurately match those on copy.
(4) Put job number, reference notes, and color of separation drawing on sheeting.
Caution: Make sure sheeting is kept clean
throughout procedure. Hand contact leaves a thin film of grease that prevents ink from taking uniformly and causes it to flake off. Any spots or dirt will reproduce on negative or plate.
(5) Then, draw all map detail exactly to size except where colors are to bleed (overlap) into each other. (Slight misregister or variation in paper size may require enlarging color areas or thickening lines to prevent gap between adjacent colors.)
Note. Positives for preparing contact negatives are drawn on standard .008-inch matte-acetate sheeting.
(6) Positives for use directly in the exposure of deep-etch or gum-reversal plates are drawn in reverse (reading right to left) by turning the map copy face down on the light table to serve as a transparency. When the positive is to be made from opaque or mounted copy, it should be drawn
22
on a thin (.003-inch) acetate sheeting. The thin sheeting will reduce the distance between the drawing and the press plate, resulting in less undercutting (spreading of light) when press plate is exposed.
b. Procedure for Negatives. Negatives are similarly drawn directly from original copy, using cellophane ink or opaque to draw in nonprinting areas.
29. Blue-line Separations
In preparing a set of color-separation drawings, close register between detail appearing on different color plates is obtained by making duplicate prints from a key outline negative. These prints are usually prepared as blue lines by the blueprint process. Blue lines do not interfere with the lithographic process and are eliminated photographically when the drawing is reproduced. Blue-line prints are prepared on any of the drawing mediums, including mounted drawing papers, lacquered plates, matte-acetate sheeting, and lithographic press plates. The solutions, exposure, and processing for all mediums are identical if their surfaces are clean. Preparation differs only in methods of cleaning before sensitizing with blueprint solution.
a. Lithographic Plates. Since lithographic press plates are used for printing, they must be prepared for lithographic reproduction by counter-etching before sensitizing with blueprint solution.
(1) Place plate (grained side up) in sink and flush with water.
(2) Pour counter-etch solution (par. 87Z?) over plate, immediately spread with brush, and distribute with quick circular motions over entire plate.
(3) Flush plate with water, removing loosened surface dirt with scrubbing brush.
(4) Place plate in whirler while still wet, set whirler roating at about 35 to 40 rpm, and flush plate with water. When dripping off corners nearly stops, flow blueprint solution (par. 877) onto plate. Use about 2 ounces for 20- by 22j4-inch plate; for other sizes, use in proportion.
(5) Continue to whirl until dry.
(6) Remove plate from whirler, wipe back and edges dry, and place on bed of vacuum frame.
(7) Place negative accurately on press plate; secure with tabs of self-adhesive tape; cover areas beyond negative detail with masking paper; close frame and apply vacuum; then, tilt into exposure position.
(8) Expose press plate to arc lamp. Use initial exposure of about 6 minutes with a 25-ampere arc lamp 48 inches away. Adjust for later exposures if required. If print is not dark enough, increase distance. Do not look at the arcs, because the light is injurious to eyes.
(9) Remove plate from vacuum frame, place in sink, flush with water, and drain for a few seconds. Again flow counter-etch solution over plate; rock to cover plate with solution; then, flush off with water and dry quickly.
Caution: Plate is sensitive to grease. Do not touch printing surface with hands.
(10) Plate is now ready for drafting with tusche.
(See par. 80 for procedure.)
b. Drawing Paper, Matte Acetate, Lacquered Plates. Blue-line prints on mounted drawing paper, matte acetate, or white lacquered plates are prepared as follows:
(1) Sensitize with blueprint solution as in (4) above.
(2) Spread solution over surface by painting with a wide camel’s-hair brush, and dry under subdued light.
(3) Expose and process as in (7) and (8) above.
(4) To develop, swab image with wad of cotton soaked in water. Intensify, if necessary, with 1 percent solution of hydrochloric or acetic acid or ammonium bichromate. Then, swab with several applications of clean water, blot off excess water, and dry thoroughly. The blue-line surface is then ready for drafting.
23
CHAPTER 4
PROCESS PHOTOGRAPHY
Section I. EQUIPMENT AND MATERIALS
30. General
The process camera is used to prepare line and halftone negatives required in map reproduction. Since the making of negatives is the first step in reproducing a map (from copy, to negative, to press plate, to printing), the quality and accuracy of the negative limits the quality of the entire reproduction sequence. The process camera is a highly accurate unit that will reproduce the map copy in exact detail and to accurate proportions on the negative. These qualities in the negative are possible because the camera is a rigid spring-suspended unit with accurately aligned movements to keep the copyboard, lensboard, and negative carrier parallel for all en
largements and reductions. (See fig. 17.) The negative end of the camera extends into the darkroom through a flexible light-tight connection. The camera can be operated both inside and outside the darkroom, to permit both ground-glass and scale focusing.
31. Copyboard
The camera copyboard is glass covered and tilts into a horizontal position for inserting the copy. A feltsurfaced spring-pressure back flattens all copy against the inner face of the plate glass.
a. Reference Lines. Center, diagonal, and rectangular lines should be marked on the felt or
/......
-e camera back copyboard
GROUND GLASS -BELLOWS LENSBOARD \ ....
_________ N. A y ' P BMCW3WMIR \ • / r-__——---—--- —
il Ml r m
r~^~y \ ill I n||j^ x Mif
1 '< va /v Ililt lilHK 1 ’ MM 1
7 7<£\ Hl nil BBIIiImT\
ft ' cyL /kf Il I U HI illll Bill mill J CAMERA ~ IMl'J
• 1 1 -I I HI MW Bill lllin 1 extension
‘TxT'LJ I' Illll NlI lllllrl indicator
kibfc-../ III III III III j I
VACUUM HALFTONE ~
BACK SCREEN 4 I A WW&jP* V—
,-T. —zSP^r''T' ***^-~-*?7 |
lensboard I HOR'ZONTAI Ze9a ' £
as OrlELiS1 p SB "r-IrtS’
.xgBPgg ef k JI ■..........................'TS1W
SCREEN-DISTANCE Z I -
INDICATOR I \
■ lensboard CAMERA
VACUUM PUMP | H DRIVE BED
AND MOTOR I IF -
^^^*»*^***' | x.
COPYBOARD Z-AXACHA .rz.
DRIVE CAMERA LEG
ARC
LAMP
Figure 17. Process camera.
24
drawn in blue on a white sheet of drawing paper that is then fastened to the spring-pressure back. (See fig. 18.) These reference lines aid in quickly positioning and aligning the copy so its image will center squarely on the ground glass and the negative.
Figure 18. Copyboard.
b. Backing. Back up thin copy with a heavy white sheet of paper. When the thin copy has printed matter on the back, use black-paper backing and slightly increase the exposure to prevent a ghost image showing through. When white-paper backing is used, cut it somewhat larger than the size of the copy to reduce the amount of opaquing required on the borders of the negative. However, too large a white area surrounding small copy is undesirable because it introduces scattered light, resulting in fog on the negative. Cover execessive white areas with black paper or cloth masks, preferably over the face of the copyboard where they also eliminate glass reflections.
c. Color Separations. Wherever possible, make all negatives in a set of color separations at the same time without shifting the locked position of the copyboard. If color-separation negatives must be made at different times, variations are minimized by making the final copyboard setting for each negative in the same direction of movement, such as toward the lens.
d. Cleaning. Keep the copyboard glass clean and free from dust, spots, and fingerprints because they may reproduce on the negative. Clean by dusting with a camel’s-hair brush and then wiping with a clean soft rag. If spots are difficult to remove, use moisture, a grease solvent (carbon tetrachloride), or a wetting agent in water (% ounce Aerosol to i gallon water). Do not use abrasive materials, dirty rags, or razor blades since these may cause surface scratches that reproduce on the negative. Cover the copyboard glass when not in use, to keep it clean and ready for operation.
32. Camera Lamps
a. Function. Camera lamps provide an intense white light to reduce exposure time for photomechanical films. This light is obtained by striking an arc between white-flame-cord carbons. The arc has a continuous spectrum, suitable for use with both orthochromatic and panchromatic film. The lamps are adjustably mounted so the copy can be uni formal illuminated.
b. Operation, (i) To operate the lamps, first insert carbons so they meet centrally and can be manually separated by about i% inches.
(2) Move lamps to end of arms and direct each lamp at an angle of 450 with the face of the copyboard (less, if direct reflections from copyboard glass reach lens). (See fig. 19.)
(3) Turn on lamps and check for uniform illumination of copyboard. Light is balanced when shadows on both sides of an object held centrally in front of the copyboard have the same tone.
(4) If illumination is not balanced, one of the lamps can be moved until balance is indicated by the shadow test.
(5) To illuminate large copy uniformly, it may be necessary to place improvised cardboard reflectors above and below the copyboard. Further improvement can be obtained by mounting paper reflectors on the sidewalls of the truck and directing the lamps against them to obtain indirect lighting on the copy.
33. Lens
a. General, (i) The lens is the “eye” of the camera. It receives light from the copy and projects it as an image on the ground glass or negative in the camera back. The process lens is color-corrected and provides a sharp, accurately proportioned image of the original copy.
(2) The lens has several glass elements with different refractive indices, ground to specific curva-
25
I
n v==p /■"/
' ' 4— =$ ■ /
CAMERA
LAMP / sy > -< Z \
/\ / \
\\ '' Z"7^V1 ^LX / XX
----\ A=X- LENS / ( /
f/\z \ A / x/x r
/ \ LIMITING LINE // \\ / ZV \
/"'>C \ \ OF REFLECTION // ' \ / / X rX
A A \ \ ,Nro LENS-Z W / / AJ
A \\ \ XZ~-y / /
r$^.CX \ / 'X ; / \
/ X \ // \> / Z \
/ \\\ /A Z\\ /// ■ \
' X / / INTO lens ' \ 1/ I
\ A / \ \z /
\ \ % NO REFLECTION \ Y / 1
\ \' x/ INTO LENS^V \ / /
\ 7\ / \ 7\ 'I /
\ -\/ X Z \ /X / '/ \/ 45 X / \/ \/
[V V t \Z i V
COPYBOARD
Figure ig. Positioning camera lamps.
tures, and mounted in accurate relation to each other, according to a complicated mathematical formula. This formula is designed to balance each type of distortion against the others to minimize distortion of the image on the negative. The lens is ground to an accuracy of a fraction of a millionth of an inch (within ^4 wave length of light), and assembled to about one ten-thousandth of an inch
erally classified by focal length, speed (maximum aperture), and degree of correction for color and astigmatism. It may also be rated by coverage and resolving power. Focal length and maximum aperture (f/number) are usually the only data on the lens. Other characteristics must either be obtained from the manufacturer’s literature or be determined
(within i to io microns).
b. Lens Classification, (i) A lens
is gen-
experimentally.
components are
Sections of several lenses and their shown
in figure 20.
CROWN FLINT A GLASS « GLASS »-------
1 W 9 J A w W w
PLANO- DOUBLE MENISCUS PLANO- DOUBLE ACHROMATIC APLANAT
CONVEX CONVEX CONCAVE CONCAVE PAIR
SIMPLE LENS SECTION
DIAPHRAGM
। Wj in
GOERZ ARTAR APO-TESSAR
PROCESS LENS SECTIONS
Figure 20. Lens types.
26
INFINITE DISTANCE
BACK
LENGTH
FOCAL PLANE
NODAL
TRUE PLANES FOCAL LENGTH—>| |<
DIAPHRAGM
NODAL POINTS
LENS
Figure 21. Lens characteristics.
DISTANT OBJECT
(2) Focal length and aperture. Focal length and aperture determine lens size and, to a limited degree, relative coverage. The focal length is the distance from the lens to the image of a distant object. In the process lens, this distance is measured from a calculated point (nodal point) in the lens system. (See fig. 21.) Aperture is the ratio of the diameter of the iris diaphragm opening to the focal length. (See fig. 22.) The diaphragm opening is slightly smaller than the calculated diameter because the light rays are converged by the front element of the lens. The diaphragm opening of an f/8 lens is % of its focal length.
(a) The area of the diaphragm opening corresponds to the light-gathering power of the lens. Since it is proportional to the square of its diameter,
a lens opened to f/8 has four times the effective area and speed as when closed down to f/16. The increased exposures required when stopping a lens down from f/8 are shown in table I.
1 able I. Change of exposure with diaphragm opening.
Diaphragm opening
Exposure ratios....
f/8 f/11.3 f/16 f/22.5
12 4 8
f/32 f/45
16 32
f/64
64
(fi) In process photography, the larger apertures (smaller f/numbers) permit shorter exposures but decrease definition (sharpness of image), coverage, and depth of focus. Accordingly, smaller apertures such as f/22 or f/32 are used for most line-negative reproductions. Stops smaller than
7T——— -------y
7-------------/ 1
I t I— T
3 5.7 4 2.8 2 1.4 1 I I (( (f/64) )) I I 1 2 4 8 16 32 64
,, -----\--\—/—/-------------/-----
-----:—\---f/22.6—-/—/------/------------t
*----------V—f A —J------------£
■*------------X. /11 -------------*
-L---------------—_______________________________v
D^R apertures area( speed)
RAT,OS c, RATIOS
Figure 22. Diaphragm ratios.
27
LENS COPYBOARD
■4 x h---I- -4- -(F)-1--1--1---1---1---t---|---|----Al—1’4 x SIZE
kl I | * 1 । I I I । ' I । ' J ।
bl A । 1 1 1 । 1 1 d 1 1
l/3x------'---1-------1--!--!---1---1---_|--J---|_J_l/3x SIZE J.
Z | । । 1 । I I I 1 U
Q h 1 1 । I II Id
G ’/2x-----1---1-A-----1--1--1---1---1---1’/a x SIZE
o y ; । Y i । ii । J
| ---j--|_-X-4]*x SIZE
u. n | i i . i । । d
« -l—p-I-
5 r 1 1 1 iii
a 1 ’/2 x I-1---1-1--------A------|___iJl’Ztx ENLARGEMENT
U I FOCAL PLANE | V i J
q^X| (GROUND GLASS) । | lid
2x ------1-1--1----1--1----A---1---1---1---t---! 2 x ENLARGEMENT
I ; I I । * I ! d I
3x------1-1--1----1--1____।___(___A___|___L_|_J 3x ENLARGEMENT
l>12 3 V 5<|
4
UNITS OF FOCAL LENGTH
Figure 23. Camera component positions.
f/45 are seldom used (except for halftones) because confusing light diffraction tends to destroy detail on the negative. 1 he f/numbers in process photography are not true ratios of aperture to focal length because the map copy is close to the lens. (See fig. 23.) General practice is to use the rated f/numbers for same-size reproduction and base all diaphragm control systems on this arbitrary standard.
(c) For an enlargement the lens is moved farther away and in reductions brought closer to the negative to maintain focus. Since the size of the lens diaphragm opening controls the amount of light passing through the lens, correctly exposed negatives for enlargements or reductions either require different exposure times or different diaphragm openings from those necessary for samesize reproduction. (See fig. 24.) Adjusting the size of the diaphragm opening is the best method ol control, especially in maintaining the constant ration required for making halftone negatives. Most of the commercial diaphram control systems operate on this principle. Table II shows diaphragm openings necessary to maintain a constant exposure time with different enlargements and reductions.
((/) Lens coverage is an approximate rating of the maximum area on which a sharp image is produced on the negative. A “sharp image” is a relative value varying with each type of photography.
Tabic II. Change of diaphragm openings for constant exposure times.
Size of reproduction
Corresponding stop No
f/51
same size 1G 2 3
f/43 f/37 f/32 f/26 f/21 f/16
In process photography, it is accepted to be the reproduction of fine type and rules without thickening or fillingfin of detail.
c. Focusing. Since map copy is held flat in the camera, depth of focus of the lens is less important than critical focusing of the image. If all fine detail on the map copy is to be reproduced on the negative as a sharp image in proper proportion, the entire area of the copy must be in focus. The process camera is calibrated to designate the correct positions of copyboard and lensboard for specific enlargements or reductions. For other lenses or ratios, the approximate positions can be computed' from the following:
(1) Distances:
Copy to lens = Focal length x (1 -|- 1 )
magnification
Lens to negative = Focal length x (1 -j- magnification)
28
STATE BSLLEBfc l-UK VVM»
LIGHT SOURCE LIBRARY
|2---t-----P---------f“1-------------------1
FOCAL LENGTH . _______'
'-. ’" o Q T Q 3
-2 x SAME ]y, x o ov q „
NEGATIVE PLANE S|ZE 2x 2% x 3x
Figure 2.J. 1 Humiliation principles.
For approximate distances the rated focal length of the lens and the lens center can be used in the formulas. If exact distances are desired, as in calculating a focusing chart, the true focal length and the positions of the nodal points must be used.
(2) Several examples of using a 19-inch lens follow:
(a) Same size as copy:
Copy to lens = 19 x (1 -f- 1 ) = 19 x 2 = 38 inches
Copy to negative = 38 38 = 76 inches
(b) Half size of copy:
Copy to lens =i9x(i-f-|) = 19 x 3 = 57 inches
Lens to negative = 19 x (1 -f- ) = 19 x
1/2= 28% inches
Copy to negative = 57 28J4 = 85JZ
inches
(c) Twice size of copy:
Copy to lens = 19 x (1 -]- %) — 19 x 1% = 28j4 inches
Lens to negative = 19 x (1 fl- 2) = J9 -x 3 — 57 inches
Copy to negative = 28% + 57 = 85% inches
Note. When increasing the ratio of enlargement, the lensboard is always moved away from the ground glass and the • copyboard is moved into focus. When decreasing the ratio of enlargement, the lensboard is brought closer to the ground glass. (See fig. 23.)
(3) Critically sharp visual focusing may not always agree with scale positions because of errors in the lens.
Note. These lens errors may cause the following: center and edges not simultaneously in focus due to curvature of the field (focused image in a curved plane) ; image goes out of focus as lens is stopped down (spherical aberration) ; visual focus does not agree with photographic focus due to chromatic aberration (focal length varies with different colors of light). (See fig. 25.)
Therefore, a job requiring the highest possible degree of definition should be critically focused on the ground glass, by stopping the lens down, inserting the color filter to be used, and examining with a magnifier.
29
30
CONVERGENCE /INTERMEDIATE ZONE
DISTANCE VARIES /
'fSP I * THROUGH /
DIFFERENT ZONES .'OUTER ZONE
FUZZY
IMAGE
LENS
SPHERICAL ABERRATION ^COPY
BLUE ~ WHITE
greenUGHT RAYS
RED'^*^^^U DECOMPOSED
- J k INTO SPECTRUM
COLORS/
>i
COLORED
IMAGE S
LENS
CHROMATIC ABERRATION ^COPY
--- SHARP IMAGE
F FORMED ON
SPHERICAL SURFACE
: ON FLAT \ / --|
SURFACE IN FOCUS \ s'*
IN ONE ZONE ONLY LENS X>\
CURVATURE OF FIELD 'x ^^copy
IMAGE IN
FOCUS |V\
/ IMAGE CURVED ' '■
BY LENS V'WZ^ I *
(EITHER CONCAVE —
OR CONVEX) LENS
DISTORTION ^^^copy
Figure 25. Lens distortions.
d. Care of Lens and Lensboard, (i) Lens. The lens requires the most exacting care and attention. It is a delicate precision instrument, and can be permanently injured by careless handling or shock. The filter slot must be kept closed and the lens caps attached at all times when not in use. Cleaning must be reduced to a minimum. When
cleaning is necessary, first dust with a clean camel’s-hair brush used for this purpose only, then breathe on the lens and wipe carefully with lens tissue. The lens is taken apart for cleaning only when excessive dust accumulates on the inner surfaces, and then only by someone experienced in handling lenses.
(2) Lensboard. The lensboard and its carriage
■n®
RED (A) FILTER
GREEN (B) FILTER
BLUE (C5) FILTER
YELLOW (K2) FILTE
65%
■T flgio%g 40% H7o%jfli%flfli%B A <
■■ ■
■■■■■kJ flflflr^-' ■ -\
■sg L J _ A
RMO%MB 25%B 80% 87% 88% 90% \x(
■■ v jr y
_L—..L......J_i
(APPEARANCE ON PRINT)
Figure 26. Color separation with filters.
31
45 ENGRAVED LINES
ON 3 32" COVER GLASS
BINDING X / Zl '~3fc; «
/ / \.-'WILl ■ w&v
z—_—/ \
VT-^X,g-— --* L—-............-.....-. A
135° LINES ENGRAVED
ON 5 32“ BASE GLASS
SECTION OF ENGRAVED HALFTONE SCREEN
SECTION OF VIGNETTED DOT, HALFTONE SCREEN
Figure 27. Halftone screens.
require less adjustment and attention than other parts of the camera, although accuracy in setting and freedom from play are important. The front surface of the entire lensboard should be dull black to prevent its reflection by the copyboard glass appearing as a ghost image on the negative.
34. Color Filters
Color filters transmit light of a selected color (or range of- colors) to the exclusion of others. (See fig. 26.) They are inserted in the camera lens when correcting color values or making color-separation negatives from map copy. Color filters are usually furnished in sheet-gelatin form and should be mounted in the split stops and secured with a single tab of cellophane tape (to permit it to expand without forming wrinkles). Gelatin filters are easily injured and must not be touched or subjected to moisture. I hey must be kept in separate identified envelopes. Dust can be removed by brushing lightly with a clean camel’s-hair brush, but excessively spotted or damaged filters must be replaced.
35. Halftone Screen
I he halftone screen is used in the process camera to break up the continuous-tone image of a photograph into a pattern of minute dots of various sizes. This pattern appears as a continuous-tone
picture to the unaided eye. Halftone dots are necessary because lithographic printing either transmits a solid deposit of ink or omits it entirely. Shades between white and black must therefore be composed of dots of various sizes to present the illusion of light and shadow. (See fig. 1.)
a. Description. The halftone screen consists of two glass plates with engraved or photographically prepared fine parallel opaque lines cemented together with the lines at right angles to each other. (See fig. 27.) The lines are normally equal in width to the clear transparent areas between them and are commercially available in standard rulings ranging from 55 to 400 lines per inch. The 100- and 120-line, screens are used in periodicals, the 133-line ruling in the better-quality book, calendar, and lithographic reproductions, and the 150-line and finer rulings in fine art and scientific or medical book illustrations. Field mapping units are provided with a 133-line glass screen and 150- or 300-line contact screen. (See par. 36.) Finer-ruled screens reproduce detail approaching the photographic original, but require more exacting control of all operations from plate graining to final press work.
b. Halftone Theories, (i) Penumbral. There are several theories to explain the formation of halftone dots on the negative. The simplest is the penumbral (shadow) theory that the maximum inten-
32
PA. 1^ AnfW...- /J r:, a I j”fer* __ _____—— ——
___ |9gz ~~______---------------------—----—--------
' ’’ "" '—'—~~ __________________- __~ ____
' : " ’, ” \ LENS DIAPHRAGM
PRINCIPLE 1 \ \
OF NEGATIVE SURFACE HALFTONE SCREEN
DOT FORMATION
Figure 28. Halftone dot formation.
sity of light reaches the film through the center of the halftone dot opening, and that the light intensity gradually falls off until a minimum is received underneath the center of the intersection of the halftone rulings. (See fig. 28.) The size of dot formed under each halftone screen opening is directly dependent upon the quantity of light reaching it from the corresponding area on the copy.
(2) Diffraction. A more acceptable theory explains the formation of the halftone dot as a diffrac-
tion pattern, the halftone screen being considered as a diffraction grating. When light passes through a small screen opening it interferes with itself, projecting a central maximum (bright spot) surrounded by a series of concentric rings of diminishing light intensity. These rings are the second, third, fourth, etc., maximums. By this theory, the screen distance is correct when the second maximum from each screen opening is superimposed on the central (first) maximums of adjacent screen openings. The intensity of light falls off to a minimum between the
opening. (See fig. 29.)
1
MAX —I------------------------------------------
3rd MAXIMUM ____________- — —j —
MIN __________________—-—---------— _________ D
MAX Tx^—^Zh^Jnd MAXIMUM _ ________‘__‘ "*23____—^7—
min r'f ___—
YX****^-.-1—---- —------- --LENS DIAPHRAGM
MAX 1st MAXIMUM <- OPENING
Ml N 41 — , __ _
MAX ______--------------------------------,
min rQ 444~~~'~~I ,r
F^'T
) MINIMUMS: light from edges of screen are odd-numbered multiples
I of ’Zz wave length apart and interfere with each other's
) intensity.
' SCREEN
RULINGS
MAXIMUMS: light from edges of screen are multiples of 1 wave
^NEGATIVE length apart and add to each other's intensity.
Maximum intensity behind each screen opening is sum of first maximum plus second, third, fourth, and further coinciding maximums from other openings.
Figure 29. Diffraction theory of dot formation.
33
c. Mounting Screen. Before positioning the screen in the screen holder, cover the spring clips with tabs of self-adhesive tape to prevent chipping the screen glass. Next, place the screen on the bottom of the holder with its marked (cover-glass) side away from the lens. Check the front clips to make certain they touch the screen binding only and do not extend up to the glass. If they rest against the screen glass, either file them down or raise the glass area above the clips by fastening small pads of cardboard or several layers of self-adhesive tape to the bottom of the clips. Then, carefully lower the top screen-holding bar until the clips overlap the face of the binding but do not touch the glass. Secure the upper bar in this position.
d. Setting Screen. In operation, the halftone screen is mounted between the lens and. the negative parallel to and relatively close to the negative. (See fig. 30.) The separation between screen and negative must be uniform over the entire area to control dot size uniformly. The exact distance between the screen and the negative depends on the screen ruling, and must be coordinated with the diaphragm opening in the lens to produce the desired dot in the negative. Table III lists optimum screen distances for various screens. Screen is adjusted to the correct screen distance as follows:
(1) Provide working space around screen by removing rear bellows section.
Table III. Screen distance
Screen 100 120 133 150 175 200 300
Screen distance to rulings (inches) 30/64 20/64 17/64 13/64 9/64 7/64 3/64
Distance * to glass surface (inches) 26/64 16/64 13/64 9/64 5/64 3/64 —
* This assumes an average cover-glass thickness of 3/32 inch. This is optically equivalent to approximately %-inch air distance, because the refractive index of glass is approximately iy2 that for air.
(2) Select screen-distance wedge for desired separation (1%4-inch marking for 133-line screens).
(3) Mount film on vacuum back and close back to exposure position.
(4) Set screen-distance indicator to an easily reset reading, such as .200 inch on the dial or inch on the scale indicator.
(5) Insert screen-distance wedge between screen and film at one corner of screen until it just touches both without applying pressure. Read marking on wedge at edge of screen glass.
(6) If screen distance differs from optimum value, close or open screen gap by turning adjusting
VACUUM BACK
NEGATIVE
SCREEN RULINGS
LENS DIAPHRAGM
LENS
SCREEN DISTANCE SETTING
ACTUAL SCREEN DISTANCE
CAMERA EXTENSION
Figure 30. Screen location.
HALFTONE SCREEN
34
screw slightly. Check separation and repeat adjustments until optimum screen distance is obtained.
(7) When first corner has been correctly positioned, repeat procedure for other corners until each is set to the optimum separation (13/64 inch for 133-line screen). Then recheck all corners and readjust if necessary.
(8) On completing adjustments, replace bellows. Check that screen-distance indicator is still at value set in step 4. Then, lock screen-movement stops for this position so it can be readily reset when required.
e. Contrast Control. Photographs have a longer scale of tone gradation and contrast than can be obtained by halftone printing. When making the halftone negative this longer scale can be condensed or any portion of it expanded into the limited printing range by varying the screen distance or the lens apertures. Adjusting the lens aperture is preferred because it requires a minimum of materials and controls. (See fig. 24.) The commercial controls and many devices prepared by camera operators are all variations of this basic system.
Variable-aperture systems provide two types of halftone negative control. Constant exposure times for various enlargements or reductions are obtained
by varying the apertures so light intensity reaching the negative remains constant. Contrast is altered by dividing up the total exposure required by the negative into two or more exposures through different apertures, proportioning these to produce the required contraction or expansion of the photographic tone scale. (See fig. 31.)
Apertures used in contrast control are called the high-light, middletone, detail, and flash exposures. The middletone exposure is frequently omitted because sufficient contrast control can be obtained with the other apertures. The apertures are also designated by the numerical size of the diaphragm opening used at same-size reproduction. These numbers are further used to define the series of apertures for constant contrast control over different enlargements and reductions. The high-light exposures can be referred to as the f/16- or f/22-line, and the detail exposures as the f/32- or f/45-line. (See par. .49.)
(1) Single exposure. When photographic copy has a standard contrast and tone range, satisfactory halftone negatives can be made with a single exposure. This is done by using an intermediate stop between the detail and high-light apertures. Special stops in which the high-light and detail exposures
O 2
£ £ £ HIGH-LIGHT EXPOSURE AREA o
8 8 g DETAIL EXPOSURE AREA O O
O 8 x FLASH EXPOSURE AREA 8
£ S’ Q * < *
< o x q u_
< w
uj Q X
o o o I I
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or D£ DZ. |
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A _________________ I
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NEGATIVE ~
LENS DIAPHRAGM
Figure 31. Halftone dot construction.
35
are combined into a single aperture can be improvised. (See fig. 32.)
(2) Varying exposures through several apertures. I he principles by which contrast control can be obtained by varying the relative exposures through several lens apertures are illustrated in figure 31.
(«) I he high-light or largest aperture exposure is used for undercutting the screen lines to join the dots formed by the detail exposure. This is continued until only fine pinpoint openings will remain in the areas of the negative corresponding to the high lights of the copy.
(£) The detail exposure fills in all detail of the subject, but if used by itself produces flat negatives having large high-light dots and plugged shadows.
(c) The flash exposure (over the entire negative) provides a dense core for all dots and introduces a fine pinpoint dot in the shadow areas of the negative. This makes it possible to keep detail that would be lost if dots in these areas were omitted. The flash exposure is produced by covering the copy with a white sheet of paper, or by holding a light close to the lens, and exposing through a small aperture, such as f/90, until the desired size and density of dot is obtained.
( NL,tR
uda \ I
I [FFF NEGATIVE IF. jj
TO DECREASE CONTRAST
NO FILTER FyFs.
Fl ! ! ini
JJ n Hj slight contrast increase ^Ffl ROSE
NO 30 । x filter 1
I |J| MM U ;
TO INCREASE CONTRAST
Figure 33. Contact-screen contrast control.
adhesive tape attached to the corners. Do the same thing with odd-shaped films that do not fit the rectangular grooves on the vacuum back. When mounting the film on the vacuum back, check to be sure the entire exposure area is flat before proceeding with the exposure. Any out-of-contact areas can be detected by looking at the film from an angle so reflection from the darkroom safelight can be seen from its surface. The vacuum back must be kept clean because any projection will bulge the film, distorting the image on the negative. The vacuum pump and motor require little attention other than proper lubrication. However, when new, cold, or when operating on 50-cycle current, the pump should be run without load for 15 minutes or longer to let it warm up and so prevent overheating and possible burning out of the motor.
39. Temperature-controlled Trays
I he temperature-controlled trays are used for maintaining the desired temperature of solutions. The controlled water supply circulates through the water jacket built into the double bottom of each tray. An overflow of the circulating temperature-controlled water provides a constant supply of fresh water for washing the film. Complete instructions covering operation, service, and repair of the temperature-controlled trays and associated equipment are given'in the instruction manual furnished with the unit.
40. Timers
Three types of timers are furnished with the mobile units. 'Hie interval timer is adjustable to %-minute inteivals and has an alarm which sounds when the time is up. It is used for long exposure or development periods. 1 he sweep second timer has a large readily visible sweep second hand preferred for close control in negative development. The electric interval timer automatically terminates the exposure at the completion of the set time and is used when repeated exposures of the same duration must be made.
41. Exposure Meters
An exposure meter is included in the process-camera set. It is used to determine the light intensity on the copy so the camera-lamp distance or ’ exposure times can be adjusted to compensate for varying voltages, for the color of the copy background, and for the position of the arc lamps. The meter can also be used as an improvised densitometer if the photoelectric cell opening is covered with a mask or a black-paper cone having an opening of about % or inch in diameter. It is placed in front of a bright light at a distance so the meter reads too (or some other easily divisible number) without any intervening film. This reading represents 100 percent light transmission. Density readings of negative areas taken with the meter are shown in table IV.
42. Safelights
a. Principle. Safelights are used to illuminate the darkroom. They furnish a light that is relatively safe for the photographic materials being processed. Since the photographic materials cover a wide range of sensitivity to light and color, a corresponding series of safelights are supplied. When using regular or color-blind emulsions, sensitive to violet and blue light only, the green yellow (series OA) or light orange (series o) can be used. For orthochromatic emulsions, a deep orange (series 1) or the darker red (series 2) safelight must be used according to the sensitivity of the emulsion. Panchromatic emulsions are sensitive to all colors and should be processed in total darkness. Occasional observation under a dim green light' (series 3), to which the dark-adapted eye is most sensitive, can be made without seriously fogging the emulsion. (See fig. 34.)
b. Use. Since safelights are only comparatively safe, they must be kept as far from the work as possible to still permit observation. Light leaks, high-wattage bulbs, and bleaching of the lamp filters may create an unsafe condition. Illumination should be periodically checked by putting half-covered
1 able II . Negative densities
Percent transmission. . . 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Density 1.30 1.00 .83 .70 .60 .52 .46 .40 .35 .30 .26 .22 .19 .15 .12 .10 .07 .045 .02 .00
38
sheets of film in the working areas for twice the normal handling and developing period. If fog appears on the exposed area of the developed negative, the light is not safe. Natural amber or ruby incandescent bulbs are furnished for general lighting. They are not as safe as safelights but are satisfactory if kept at some distance from the sensitized materials.
43. Miscellaneous Darkroom Equipment
Thermometers are fragile and easily damaged if dropped or abused. High temperatures above the maximum scale reading may burst the bulb, and severe jarring may separate the mercury column. A separated column can sometimes be reunited by swinging the thermometer rapidly with the bulb outward. Some thermometer stems have a bubble in the top of the capillary column. This bubble space can be used to reunite a separated column by slowly and carefully heating water in which the bulb of the thermometer is immersed until the gap in the column rises just into the bubble space, when the ther
mometer is removed and allowed to cool to room temperature. Graduates, funnels, scale pans, stirring rods, and trays must always be kept clean to prevent contaminating the solutions with previously used chemicals. Graduates must be held level for reading and the quantity determined by sighting the graduation along the underside of the liquid level.
44. Photographic Materials
a. Photographic Negative. A satisfactory map negative should have dimensional stability, high contrast, maximum density, low fog level, and reasonable working speed. These properties depend on the nature of the supporting base, and the sensitometric characteristics (photographic properties) of the negative emulsion.
Glass is a desirable base for map negatives because it is not affected by normal humidity and temperature variations. However, its fragility and bulkiness limit its use to wet-plate and dry-plate negatives in base plant operation.
Photographic negatives prepared on a film base
39
C SERIES 3 I SERIES 2
/ H----------------
SAFELIGHTS -< H---------SERIES 1____________
I SERIES 00
FILTERS -------------------G
----------C5-------------B-----------------------------A---------------
-----------------------K2----------------------------
MAXIMUM SENSITIVITY^ OF EYE ° % % LU
| O : O •> z
VIOLET BLUE GREEN > \ Q RED
© o
I o c
o o
~ ——' 1 0 z<'A’ v o ---- ■* *—©
________LA\
4.000A0- 5z000A° 6z000A° 7z000A°
Figure 34. Safelights, filters, and negatives.
are safer and more compact than glass, but are subject to changes in size caused by atmospheric changes. Low-shrink film bases (cartographic or topographic) are used for map negatives. If properly handled they are sufficiently stable for map
on one side and a gelatin coating applied on the other. (See fig. 35.) The substratum coating usually contains a dye to absorb light passing through the emulsion and to prevent internal reflection known as “halation.” Halation causes loss of
Table V. Negative characteristics
Material Processing shrinkage 1 Differential Humidity amplitude 2 Differential Temperature coefficient 4
With grain 3 Across grain 3 With grain 3 Cross grain 3
Regular film .13 .01 .12 .226 .275 .049
Topographic base film .00 .02 .02 .131 .153 .022 .000083
Nitrate base film Fiberboard .005 .000 .005 .109 .04 .136 .04 .029 .00
Zinc plates .00 .00 .00 .00 .00 .00 .0000145
Glass .00 .00 .00 .00 .00 .00 .00000495
“Vinylite” sheeting .00 ■ .00 .00 .006 .007 .001 .000039
1 Processing shrinkage is the change in size resulting from development, fixing, washing, and drying at 70° F.
2 Humidity amplitude is the percentage of dimensional change resulting from a 10 percent relative humidity change.
3 With and across grain refer to the grain of the material. The differential shrinkage or stretch between these two is important because it influences he scale of the map in the two directions.
4 Temperature coefficient is the dimensional change resulting from a rise of 1° F.
reproduction. The characteristics of negative bases are given in table V.
(i) Humidity variations. (a) The humidity within a mobile unit may vary 20 percent or more during a single day or from one day to the next. This may cause a .040 inch change in a 20- by 20-inch topographic-base film and would be about 50 percent greater for regular film. This variation is detrimental because good register should be within .003 of an inch.
(Z>) The humidity amplitude of a film is affected not only by changes in relative humidity but also by the heat of the light table and the arc lamp. Consequently, accurate register in color work requires that all negatives for a map be taken from the same box and exposed and processed in close succession. This also applies to the handling of the set of negatives during retouching, lay-out, and plate making.
(2) Photomechanical film. Photomechanical film negatives are usually prepared on a plastic base
with a substratum and an emulsion coating applied definition and introduces fog into the otherwise sharply defined boundaries between the transparent and opaque portions of the negative. (See fig. 35.) The gelatin backing keeps the film from curling during drying.
(3) Sensitometric characteristics of negative, (a) The photographic properties of the negative are contained in the light-sensitive emulsion. The speed of the emulsion depends on the method used in preparing and aging the gelatin with its silver salt. As a general rule, fine crystals in an emulsion have a correspondingly fine grain, but a slow exposure speed. Large crystals are more sensitive to light, but result in a more granular negative. Dyes incorporated for color sensitization also influence the sensitivity of the emulsion.
(Z?) The emulsion speed is an approximate rating for each batch of film. The exact speed can be determined experimentally by exposing the negative to a series of increasing exposure times and
40
then measuring the range of densities* on the resulting negative. When these densities are plotted on a chart against exposure time, the resulting curve, known as the characteristic curve, shows all the properties of the negative emulsion. (See fig. 36.)
(c) The foot of this curve represents the region of underexposure where an increase in negative density is not proportional to an increase in exposure. The straight portion is the region of correct exposure where an increase in density is directly pro
indicating that the contrast of the negative is 5 to 9 times that of the copy.
(d) If the straight-line portion of the curve is extended down to the base (or zero density line), the point of intersection is called the “inertia (I)” of the film and is frequently used in expressing the sensitivity of the emulsion. The film speed is defined as 10/I. With photomechanical films, the speed usually ranges between .2 and .5 for the regular (color blind) film, .4 to 1.0 for the orthochromatic, and .5 to 1.5 for the panchromatic. This
INCORPORATING ANTIHALATION D Y E |
.... flp fl fl
FILM BASE
I
J w
w -■--------------"----
■B NONCURL BACKING yW
ing^B^^wih^ahtihaiTtio^backin^^b
N) (BEAM ABSORBED - NO REFLECTION) [
Figure 35. Halation through film.
portional to the exposure time. The slope of this straight portion is a measure of the contrast (gamma) of the film. When the slope is 45°, for example, the increase in density is directly proportional to the increase in exposure, and the contrast of the negative is the same as the copy. If the slope is steeper, the contrast is greater. Photomechanical films used in process photography have a high contrast ranging between a gamma of 5 to 9,
*The density of a negative is a measure of its ability to prevent the passage of light. It is defined as:
incident light
log ----------------—
transmitted light
compares with 25 for “Panatomic X,” and too for “Super XX” film.
(4) Other characteristics. Other characteristics also influence the satisfactory use of photomechanical films. The optical density measured on a film that has been fixed and washed without exposure or development must be very low (usually not exceeding .02) to provide the high degree of transparency required in photomechanical negatives. The fog density of the processed film that has been developed and fixed without exposure must also be low (usually under .1). Increased fog may appear in the negative because of age, overexposure, in-
41
42
•001"SEC .01 SEC .1 SEC 1 SEC 10 SEC 100 SEC Z1000 SEC
SHOULDER r/ OF CURVE / 4------------------------------------------------------------/___________
High-contrast / photomechanical h film. I
3_______________Amateur-type Gamma = 6.0 /
orthochromatic film ~t
£ developed to normal / s,oPe of curve
contrast for contact r~ indicates contrast
uj printing. / of emulsion.
Q Gamma = 1.0 F6 /
2 \ s'"’ I'5 J*
\ / S^ / '3
X/ y /-2
y s' / 1
/ / P
/ / High-speed /
1 / panchromatic----------------f—-------------
// \ film developed TOE OF / Log inertia = 1.52
to low contrast CURVE Z (Inertia — 33
>:Fr>r ncMciTv for enlar9in9- I Speed = 12 = ,3*
FOG DENSITY Gamma = .8 JX / I
-- f I ——K
-L o 2 s
LOG EXPOSURE
Figure 36. Characteristic curves for negative emulsions.
ternal reflections in the lens or camera, dust in the air, or from storage or development above 70° F. This fog must be kept to a minimum for satisfactory control of press-plate exposures. (See fig. 37.)
quinone is used alone in most photomechanical developers because it is more powerful and develops greater density and contrast in the negative.
(b) Preservatives. The preservative (usually
EXPOSURE TIME 25 MINUTES-------------------------------------------------------------------
20 MIN----------------------------------------------------------L____________
15 MIN--------------------------------------------------_____________________
10 MIN--------------------------------------_________________________________
MIN_____________________.s'_____________Basis: 2 minutes exposure time
.s' through satisfactory negative
with clear transparent _______—— printing areas.
_ INCREASING FOG DENSITY
01——-----------------------------------I___________1_________________________
°-2 0-4 0.6 0.8 1.0 1.2
Figure 37. Negative-fog effect on required exposure.
The maximum density obtainable in a film determines the opacity of its background. It depends directly on the silver content in the emulsion, and must be relatively high for photomechanical films. The resolving power of the film is a measure of the fineness of its grain. Photomechanical films can separate more than too lines per millimeter while process lenses seldom separate more than 30 or 50 lines per millimeter.
b. Chemicals. (i) Developers. Developers are used to reduce the silver salts and bring out the photographic image on the exposed negative. (See fig- 38-) They are made up of chemical agents called “reducers,” “preservatives,” “accelerators,” and “restrainers.”
(a) Reducers. The reducer is the active ingredient in the developer. It is chosen for its ability to selectively decompose the silver salt in the emulsion in proportion to the amount of light reaching the negative. Hydroquinone and metol (elon) are the reducing agents used in developers. Hydro
sodium sulfite) increases the life of the developer by slowing down oxidation. Since it also increases development time, only enough preservative is included to provide a satisfactory working life.
(c) Accelerators. The accelerator (an alkali such as sodium carbonate) speeds up development by swelling the gelatin emulsion to permit more rapid penetration by the reducer. Too much accelerator will fog and soften the emulsion. Paraformaldehyde is used in many photomechanical developers because it is less injurious than alkaline accelerators and also tends to harden the emulsion.
(tZ) Restrainers. The restrainer (usually potassium bromide) holds back development of fog, tending to keep transparent areas of the negative clear.
(?) Concentration of developer. The concentration of the developer in water has a direct bearing on the characteristics of the negative. Dilution tends to decrease contrast and increase fog, while higher concentrations than normal may increase both contrast and fog. Extreme dilution can be
43
44
I I 1 I PROJECTED LIGHT IMAGE ON NEGATIVE pn_________________________________________
SILVER-SALT Jt//
EMULSION -_________
ANTIHALATION BACKING/^
METALLIC SILVER
DEPOSITED-----------------------'xgV''
SILVER-SALT EMULSION--------------< '
i- I Y~Z STORAGE
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---6~I ^VACUUM _ )L—LI ------------ .............................
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£ J. PROCESS CAMERA r. W N
N IV rAMFPA COPYBOARD
S DARK ROOM J \ ‘ ArC
......................II Vz lAMP -----------------------------------------------1-J|-......... tSr' 1 . *' TRUCK-BODY......................................................WT^I
EXTENSION U
STEPS
Figure 40. Process camera section.
Section II. NEGATIVE MAKING
45. General
A correctly exposed and processed halftone negative must not only have a maximum range of tone values, but must also be compensated for the nature of the copy, the color and finish of the paper stock, and the press conditions. Proper press control and good equipment can reproduce halftones with little change of dot or tone value, but such conditions are not always attainable. Consistently inferior printing arising from plate-making or press shortcomings may be evidenced as a sharpening of the work with a loss of high-light dots, or as a gain of printing density. This may increase dot size as much as io to 25 percent. Compensations can be made in the negative until plate or press conditions are rectified. Inferior printing may also originate from improperly prepared halftone negatives.
46. Preparation
Before operating the camera, the following preventive maintenance measures must be taken:
a. Lubricate rails, gears, shafts, vacuum pump, other moving parts of camera, and temperature
control equipment in accordance with instructions appearing in the respective Technical Manuals. Do not oil moving parts of lens.
b. Clean trays or tanks, graduates, pails, stirring-rods. and paddles. Prepare all necessary developing, washing, and -fixing solutions. Then mix developing and fixing solutions, bringing their temperature as close to 67° F. as possible. Pour them into the proper trays or tanks. Also keep the water as close to 67° F. as possible, using temperaturecontrol system or improvised heating and cooling means when temperature control is not available or is inoperative.
c. Provide adequate ventilation when using solutions containing formaldehyde or acetic acid. Wear rubber gloves when using continuous-tone developers or intensifiers. (See par. 56.) Avoid looking directly into arc lamps because repeated exposure to the intense light is injurious to sight.
d. Make certain lens is securely mounted in lensboard, and that lensboard is locked in position.
e. Slide camera lamps to end of their supporting arms and secure them in correct position and at
46
proper angle. Then insert carbons and adjust them so they meet centrally and can be separated by at least inches when the arms are pulled apart.
f. Clean copyboard glass if necessary. (See par. 3^-)
47. Line-negative Procedure
a. Examine map copy for injuries or omissions. Be sure all required markings and instructions have been furnished.
b. d ilt copyboard into horizontal position by releasing catch at its base. Unhook latches and raise upper glass frame of copy board until it catches and holds in raised position. Then place copy centrally in copyboard, aligning it to previously prepared reference marks. (See fig. 18.) Dust copy carefully with camel’s-hair brush, lower glass frame, secure latches, release catch, and tilt copyboard back into vertical position. Examine copy and glass again to make certain no dirt or dust appears on its surface.
c. Next, move copyboard and lensboard carriages to particular ratio of enlargement or reduction indicated on the scale or by chart readings. (Set nearest predetermined ratio when final size is to be scaled on ground glass.) Then secure lensboard driveshaft with hand lock.
d. Remove lens cap, placing it face downward so it will not collect dust.
e- Open lens shutter and lens diaphragm as wide as possible. Make certain screen mechanism is withdrawn and ground glass is fully lowered into contact with camera back. Switch on arc lamps and examine image of copy on ground glass. Using lensboard adjustment controls, move image vertically or horizontally until centered on ground glass.
f. Measure image with steel rule or beam compass or check dimensions with previously prepared markings on the ground glass. If adjustments are necessary, change lens and copyboard positions until exact size and critical focus are obtained. This is most easily done by first moving the lensboard away from the ground glass for a larger image or towards the ground glass for smaller image, and then relocating the copyboard to return the image into focus. (See Par. 33c.)
g. Close lens shutter and set lens-diaphragm control so the f/32 line agrees with number on camera extension indicator dial on side of camera. This
automatically compensates for position of lens. Turn out all lights in darkroom behind camera except for safelights required for the negatives to be used, and close darkroom door.
Note. Expose a test strip before making first map negative and at the beginning of each day or every time a new type film is used. This test strip is used to verify exposure time required by the film and to check condition of developing and fixing solutions. To prepare test negative, first attach a small strip of film to vacuum back by vacuum suction or with several pieces of self-adhesive tape. Then raise ground glass and bring vacuum back into exposure position. Switch on camera lamps and expose film by opening shutter for required time. Then close shutter and turn arc lamps off. The first test exposure for photomechanical orthochromatic film should be 40 seconds with lens stopped down to f/32 line and with copyboard illumination of 200 feet candles (Weston light meter) on white area of copy. Relative exposures for other films are given in table VI. After exposure, close shutter and turn off arc lamps. Remove film from vacuum back and immerse in a freshly prepared developer. If solutions and exposure are correct, the image on photomechanical film appears in between 30 to 45 seconds. If image appears sooner, the film is over exposed and another test strip must be exposed for a shorter time until image appears within 30 to 45 seconds. Conversely, if a longer time is required, exposure must be increased. Full development should be reached within 2 to 3 minutes. Under conditions where temperatures cannot be properly controlled, total developing time should be about four times that required for the first appearance of the image.
Table I I. Negative exposure guide.
Weston GE Relative exposure on process camera, f/32 (seconds)
Daylight Tung-sten Daylight Tungsten
Kodalith Orthochromatic. . .5 .2 40
Reprolith Panchromatic.... .7 1 30
Commercial Ortho 24 8 40 12 I
Panatomic X (Finopan).... 24 16 32 24 1
Super XX (Superpan press). 100 64 150 100
h. Place negative centrally on vacuum back of camera with emulsion side (dull side) towards lens. Open vacuum valves necessary to hold film flat. Swing vacuum back into exposure position, turn camera lamps on, open shutter, and expose negative for proper time as determined with test strip.
1. Remove film from camera, switch off vacuum pump, and proceed with development.
47
j. In tray development, immerse negative quickly and uniformly into developer by drawing negative through developer face down and then turning it over face up. Rock tray to make certain entire negative is covered by the solution. Continue rocking tray until development is completed. Then remove negative and immerse momentarily in a second tray with water or short-stop solution. Next transfer negative to third tray containing fixing solution, where it should remain for double the time required to clear the last traces of unexposed silver salts from transparent areas of negative. After fixing, place negative in water tray for 5 to 10 minutes to wash away fixing salts. Remove negative and examine over light box or against sheet of white paper. If negative appears veiled or fogged so transparent areas show a decided grayness, clear negative with a clearing solution.
k. If clearing is required proceed as follows:
(1) Prepare clearing solution (“Farmer’s Reducer”), preferably in advance according to instructions on container (or see par. 56/).
(2) Immerse film negative in tray containing this solution. Rock tray or sponge negative with clean tuft of cotton until transparent lines are no longer clouded but show clearly against tray or white piece of paper. This normally takes 5 to 30 seconds. Immediately after clearing, return negative to wash tray and wash for 5 to 10 minutes as required for normal film.
I. If an additional tray is available, fill it with clean water containing a wetting agent (such as % ounce Aerosol to the gallon). Immerse negative for a few seconds before proceeding with drying.
m. Dry negative by carefully blotting between two sheets of lintless blotting paper, or remove surplus water with a dampened cellulose sponge. Then, suspend film in rack or on lines near a fan so circulation of air hastens drying.
n. The negative is now ready to be prepared for the press plate. However, before being released, check accuracy of detail and dimensions of image to guard against errors. Slight variations in size may be noted because of stretch or shrinkage of the him due to its retained humidity.
48. Halftone-negative Procedure
Material, equipment, and solutions for making halftones are similar to those used in line work. Normal procedure follows:
a. Prepare camera and solutions as described in steps a through d, paragraph 47. Place a gray
scale along one side of copy so it will appear on negative.
b. Install halftone screen and adjust distance as described in paragraph 35c and d.
c. Expose and process a small test negative of a portion of copy, preferably including gray scale. Examine under a magnifying glass to assure that dot formation is correct. (See par. 35c.)
d. Mount negative (emulsion side towards lens) centrally on vacuum back, and swing the back into exposure position.
e. Expose negative for its high-light, detail, and flash exposures. When a Douthitt diaphragm control is furnished, procedure is as follows:
(1) Attach dial designated for the 133-line screen to camera-extension indicator. Adjust dial at time of installation so indicator reads “7” when lensboard is positioned for same-size reproduction.
(2) Note reading on camera-extension dial.
(3) Position lens-diaphragm indicator so it points to same reading on f/16- or f/22-line (high-light exposure series).
(4) Select contrast correction desired from figure 43.
(5) Expose by switching on lights, and removing lens cap for designated time shown on exposure chart.
(6) Move lens-diaphragm indicator to same dial reading on f/45 line (detailed-exposure series).
(7) Make detail exposure by removing lens cap for time designated for same correction on exposure chart. (See fig. 43.)
(8) For flash exposure, hang a sheet of clean white paper in front of copyboard and stop lens down to f/90.
Note. To use rotating flash stop furnished with Douthitt diaphragm control system for flash exposure, select an opening with a number 50- percent larger than that indicated on camera-extension dial. It is better to use the f/90 position on the lens-diaphragm ring (or position on f/45 line corresponding to one-half the number indicated on cameraextension dial) to obtain uniform results. This is recommended because a slight displacement of the opening in the rotating flash stop from the diaphragm’s optical center will cause nonconcentric dots.
(9) Proceed with flash exposure the same as for high-light and detail exposures.
(10) Switch off camera arc lamps.
f. Remove negative from vacuum back and stop vacuum pump.
g. Immerse negative quickly in developer by drawing it through solution face down and turning it over. Rock tray to circulate solution and facilitate
48
uniform development. Continue developing for 2 to 2% minutes at 67° F.
h. The image should appear in 30 to 45 seconds if total exposure time is correct. If the image appears sooner, negative is overexposed. If it takes longer to appear, it is underexposed and exposures on the high-light, detail and flash stops must be increased proportionally to obtain the desired contrast. Where temperature control is not available, development time is about four times that for first appearance of the image.
i. Immerse negative in water or short-stop tray for a few seconds; then place in fixing-solution tray until cleared. Next transfer negative to water tray for a few seconds. Examine with magnifier on light box or table. If exposure and development are correct, the gray scale on the side of the copy reproduces in all its tones. With normal copy both the gray scale and the copy have a complete range of dot sizes varying from a small opaque pinpoint dot in the clear area corresponding to shadows to a nearly blocked-out area with small clear pinhole openings corresponding to high lights on the copy.
j. If the entire negative is too light with no opaque dots in the shadows and with a fairly open dot in the high lights, the negative is underexposed or underdeveloped. If development is correct increase all three exposures proportionally until desired dot range is obtained.
Note. If negative is too dense with smallest dots comparatively large and pinhole openings in darker portions of
the negative entirely veiled or fogged, negative is overexposed or overdeveloped. The screen distance may be too great, or stop opening too large. If time, temperature, screen distance, and stops are correct, shorten exposures proportionally.
k. Examine for veil between dots by viewing negative through a magnifier over a light box or against a white sheet of paper. If transparent areas show fog, they are cleared with Farmer’s Reducer as described in paragraph 47^.
I. Place negatives in wash tray again for 5 or 10 minutes. A wetting agent can be used for a final rinse to assist uniform drying. Then blot with photographic lintless blotting paper, and hang on line near fan to dry.
in. Check negative for size, injuries, correct dot formation, and inclusion of data. If satisfactory, it is ready for opaquing and lay-out.
49. Improvised Halftone Negative Controls
a, When a lens diaphragm control system is not available or is inoperative, halftone negatives can be made either by approximating the stop-opening positions between the markings on the lens barrel, or by adding an indicator and marking a scale for the basic and intermediate positions. Using the f/16- or f/22-series for the high lights, the f/45 for detail, and the f/90 for the flash exposures, the corresponding values of these diaphragm openings for other ratios of enlargement or reduction are given in table VII.
Table VII. Alternate diaphragm control system
Ratio of reproduction High-light exposure Detail exposure f/45 basis Flash exposure f/90 basis For linenegative control f/32 basis
For variable flash (constant exposure time) For constant flash at f/90 (varying times) multiply time by —
f/16 basis f/22 basis
3 x size f/ 8 f/11 f/22 f/45 614 f/16
2% x size 814 1114 24 48 514 17
214 x size 9 1214 25 52 4 18
214 x size 9M 1314 27 55 314 1914
2 x size 1014 14 29 60 214 21
114 x size 1114 16 32 66 2 23
114 x size 1214 1714 f/36 f/72 H4 f/25 J4
114 x size 14J4 1914 40 80 U4 2814
1 (same size) 16 22 45 90 1 32
14 x size 1814 25 51 103 9 37
J4 x size 2214 29 60 120 8 43
14 x size 2514 35 72 144 % 51
49
b. I he contrast of the copy is judged by comparing the negative with the exposure control chart. (See fig. 43.) The negative is then exposed according to the recommended exposure times appearing under the illustration for the desired contrast.
c. Exposure times are based on a reflected light intensity of 200 foot-candles on a white area of the copy. For other intensities change exposure times accordingly. If the tone range of the copy does not exactly correspond with any of the nine tone steps illustrated, corrected exposure times are estimated by interpolating between the nearest figures. Samples of various types of copy marked with the most satisfactory exposure and processing should also be kept for use in judging further copy.
50. Intensification and Reduction
Intensification of the negative increases the density of each silver grain in the emulsion by adding silver, compounds of the heavier metals (chromium, mercury, copper, or uranium), or coupling dyes. For photomechanical negatives, the silver cyanide (Monckhoven) intensifier (par. 56/1) is preferred because it does not fog the film and tends to clear the transparent areas while adding density to image areas of the negative.
a. Intensification. Photomechanical negatives are seldom intensified because a new negative can be made in less time. However, intensification may be desirable for dot etching or to improve a negative when there is a shortage of negative materials.
b. Reduction. Photographic reducers are frequently used on photomechanical negatives as a clearing agent to remove any exposure or development fog that appears during the processing. A fog density of only 0.3 in the clear areas of a negative will double the exposure time required in printing from this negative. Since it is difficult to estimate the exact density of the fog and its influence on plate-making, the negative background must be completely cleared to obtain satisfactory press plates.
51. Desensitizers
Desensitizers are used before or during development to make possible the processing of the negative in a i airly bright light. However, desensitizers are not furnished to field map reproduction units because most photomechanical emulsions used can be processed under fairly bright safelights.
52. Wet-plate Process
The wet-plate process is one of the earliest methods
for preparing photographic negatives. It is now obsolete for most photographic purposes, being superseded by dry plate or film, but is still used to a limited extent in base-plant map reproduction work. Wet plates are superior to dry plates in sharpness of definition and the ease in which they can be intensified, reduced, or engraved.
a. Description. In the wet-plate process, the entire handling of the negative during exposure and development is conducted while the plate is wet. Since the plate is relatively slow in speed and is color-blind, it can be used only for exposures that can be completed before the drying emulsion reaches the image. This will usually be 8 to 10 minutes if working margins around the image are sufficiently large.
b. Preparation. To prepare a wet-plate negative, first clean the glass thoroughly and then apply an albumen substratum coating. Just before the plate is used, flow a collodion solution containing the iodizer (potassium iodide) over the plate by hand and let it set as a uniform coating. Then, sensitize the plate to light by placing it in the silver bath (containing silver nitrate) for about a minute to let the potassium iodide combine with the silver nitrate to form silver iodide in the collodion. Next, drain the excess solution off plate and place directly in camera for exposure. Following exposure, develop the image with an acidified iron sulfate solution. Clear with a cyanide solution, intensify once or twice by bleaching with a copper-sulfate-potassium bromide solution, and blacken with silver nitrate. Further local 1 eduction or intensification can then be carried out. Protect the completed negative with a gum-arabic or varnish coating. If the image is to be sti ipped from the glass support and combined with another negative, two protective coatings consisting of a rubber solution and a stripping collodion solution are applied to strengthen the film.
53. Using Color Filters
I he function of color filters is to separate a particular color or range of colors to photographically record the colors on the negative. (See fig. 41.) The choice of the color filter depends on color of original copy, nature of illumination used, color sensitivity of negative, colors of printing inks to be used, and transmission range of available color filters. (See fig. 42.) The filter factor is the increased exposure time required by the filter. Characteristics of several filters are listed in table VIII.
50
ORIGINAL COMPOSITE COPY IN COLOR
A (RED) FILTER B (GREEN) FILTER C5 (BLUE) FILTER
COLOR-SEPARATION NEGATIVES
BLACK PRINTER
BLUE PRINTER
RED PRINTER
GREEN PRINTER
(A FILTER)
(B FILTER)
(A FILTER)
PRINTS OF CORRECTED COLOR SEPARATION NEGATIVES
Figure 41. Map color separation.
51
54. Magenta Contact-screen Halftone Negatives.
Halftone negatives are made from black-and-white copy by placing the magenta screen in contact with the sensitized negative on the vacuum back in the camera. Contrast is controlled by varying the relative exposures through several color filters, instead of changing the lens diphragm opening as is done with the glass halftone screen. The exposure guide furnished with the magenta contact screen must initially be adjusted to compensate for lighting and other conditions. Instructions for this preliminary adjustment are on the back of the exposure guide. Once these adjustments have been made, the steps in producing a contact-screen negative are as follows :
a. Prepare camera, associated equipment, and solutions as described in paragraph 46.
b. Determine contrast range and corresponding-exposures required by matching lightest and darkest portions of detail in copy with gray scales along margins of the exposure guide. Read recommended exposure times at intersection of selected highlight row and shadow column.
c. Mount copy and position copyboard and lensboard for size and focus as described in steps a through f, paragraph 47.
d. Turn off arc lamps, replace lens cap, and insert the first filter called for by selected exposure square on chart.
e. Attach upper edge of contact screen to vacuum back with a strip of self-adhesive tape. Emulsion side (dull side) away from the lens.
f. To avoid injuring the screen surface, handle only by the margins. Clean by dusting with a camel’s-hair brush. If necessary, wipe lightly with
UJ 2
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O >- O rv-
100%p=^=.|., .[. ,|y- ° ,17] . “ ——
---EFFECTIVE RANGE OF LIGHT TRANSMISSION THROUGH LENS-^V-h-
—-u"4-----------------------------------------------
% LIGHT ...........:
TRANSMITTED 80%-------------------------y /---------A— . /--------------------
NO 4 / / / /
\/ / NO 30 > / WRATTEN
7 / \ . / FILTER
/ / A; I NO COLOR
/ K2 r I I
60%-----------*--\-------A—v--z-v-----i--1--- 4 ---------LT YELLOW-
•. NO 30 / / \ : 8 (K2)_____YELLOW
: ''S 1 \ 25 (A)______RED
: •. ! \ : 30_________ROSE
; I I ! I 47 (C5)____________BLUE
/ \ I | ; I 58 (B)_________GREEN
/ / V' If ' :
40%--------f-----r----\;—-----------------------------------------
/ I \ \TI fT|
/ ' • 'J ' ■
/ I \ k I Z5 58 \ : NO 25
20%------?-----A---------------------U-f--------------------------
/ / nTl
/ I \ • \
•• / / M ' • }
/ NO47/ / J\ WAVE LENGTH
o%L_____Ty_____________ / I*—.>...■ / lsv._____
3,000A 4,000A" 5,000A° 6,000A° 7,000A° 8,000A°
Figure 42. Color-filter transmission curves.
52
Table VIII. L se of color filters.
Wratten filter No. A (No. 25) B (No. 58) C5 (No. 47) K2 (No. 8) No. 4 No. 30 Color of filter Red Green Blue Yellow Light Yellow Rose Used in exposing color color separation for— Blue printing plate. ■ Red printing plate. Yellow printing plate. Black printing plate. Also for photographing Blue as black; Green as black; Orange as white; Red as white. Violet as black; Green as white; Orange as black; Red as black. Violet as white; Blue as white; Yellow as black; Red as black. Blue as black; Yellow as white. Decreasing contrast with magenta contact screen. Increasing contrast with magenta contact screen. Negatives used Kodagraph pan Reprolith pan Kodalith ortho Commercial ortho Kodagraph pan Reprolith pan Kodalith ortho Commercial ortho Kodagraph pan Reprolith pan Commercial ortho Kodalith ortho Kodagraph pan Reprolith pan Kodalith ortho Kodalith ortho Approximate filter factor (increase exposure, multiply by) 19 / 7 40 15 22 10 3 12 17 14 3 3 2
a tuft of cotton dampened with carbon tetrachloride and wipe with a second tuft of dry cotton.
g. Turn on vacuum pump, insert negative (emulsion side towards lens) between vacuum back and contact screen, and lower contact screen down against negative. Open all valves on vacuum back leading to channels behind contact screen. If screen tends to lift away from vacuum back when brought into contact by finger pressure along the margins, place a large sheet of clean cardboard over film and press to bring screen into vacuum contact. Contact screen must be larger than the negative and should extend to a vacuum channel beyond edges of negative on vacuum back. If screen is not large enough to provide such a seal, enlarge it by adding border strips of clear film along the margins, carefully joining the screen and strips with self-adhesive tape so no waves or wrinkles are formed. Wait 15 to 30 seconds after inserting the film to let the vacuum withdraw all the air pocketed between the screen and the vacuum back. Complete contact can be observed by viewing the screen surface to reflect the image of one of the safelights.
h. Close vacuum back. Proceed with first exposure stated on exposure guide.
i. Change filters and continue with other exposures. Then, replace lens cap and switch off arc lights.
]■ Remove negative from vacuum back, stop pump and motor, and proceed with development and processing as described in steps f through m, paragraph 48.
55. Photographic Expedients
a. Salvaging Film. For reviving fogged or exposed but undeveloped process negatives. Prepare:
Ounce
Water .............................. 24
Ammonium bichromate.................. 1
Immerse about 3 minutes. Wash in water 5 to 10 minutes, blot with clean blotting paper, and hang film to dry. Conduct all operations under safelight. For use, multiply normal exposure time by four. Follow standard procedure for developing, fixing, and washing negatives.
53
b. High Temperature Development of Process Film. When temperature control is unavailable, dilute developer to obtain constant development time as follows:
Line negatives Halftone negatives
Temperature °F Dilution 1 Temperature °F Dilution
70 none 70 none
80 1:1 parts water 80' 1 parts water
90 1 :1% parts water 90 1 :1 parts water
c. Continuous-tone Negatives From Photomechanical Film.
(i) Exposure time same as for line negatives.
(2) Develop in extremely soft contrast developer, such as DK 6oa diluted as follows:
For normal copy:
i part developer to 15 parts water. Develop for 8 minutes at 67° F.
To increase contrast:
i part developer to 10 parts water. Develop for 6 minutes at 67° F.
To decrease contrast:
I part developer to 20 parts water. Develop for 10 minutes at 67° F.
Advantages: fine grain, standard materials, can be processed at high temperatures.
d. Contact Screens. Contact film screens for use either in the camera or in a printing frame for exposing halftone negatives from continuous-tone subjects are made and used as described below. Several screens should be prepared so halftone negatives can be produced if screens are damaged.
(1) Preparation of screen. Use normal screen distance. Position lensboard for three times enlargement. Open lens to f/11. Place white sheet of paper over copyboard about 12 inches in front of lens. Mount photomechanical film on vacuum back. Expose about 2% minutes. Develop in extremely soft contrast developer, such as DK6oa diluted one part to eight parts water, for 6 minutes. Wash, fix, wash, and dry as in normal negative processing.
(2) Use in camera. To use contact screen on camera, hold screen in contact (emulsion to emulsion) with negative by vacuum. (See par. 54.) Expose about 3^ minutes at f/22.
(3) Use in contact-printing frame. To use in contact-printing frame, obtain halftone negatives from continuous-tone positives by placing screen between positive and film. Expose about 30 seconds,
using 60-watt lamp at 36-inch distance. Exposure times vary depending on density of positive or tone of copy. To obtain increased contrast, turn screen film over so emulsion side is away from negative or insert thin sheets of clear acetate between screen and negative. Screen films for different contrasts can also be obtained by using flat or contrasty developers.
e. Improvised Contact-printing Methods. Contact printing can be improvised as follows:
(1) Contact negatives (or positives) can be made by using the glass-covered copyboard to hold negatives together while exposing with a concentrated light source. Move copyboard to end of rails, and hold 15- or 25-watt incandescent bulb in front of lens.
(2) Use vacuum back of camera as contact printing frame. Cover with large sheet of clear acetate sheeting, and attach with self-adhesive tape to hinge along upper edge. Insert negative and film between clear acetate and vacuum back. Then, apply vacuum to seal films together. Exposure can be either from a lamp in darkroom or through lens.
f. Color Separation by Masking, (i) Use. The British Ordnance method for producing colorseparation negatives from existing maps under urgent conditions can be used as an expedient when time is limited or camera equipment is disabled. Little opaquing or other hand work is required on the negatives. The quality of reproduced maps is only fair but is sufficiently legible and accurate to be usable.
(2) Procedure, (a) Prepare an exposure light by placing a 25- or 60-watt lamp in a box having a small opening and a slot into which color filters can be inserted. Locate the light centrally in front of vacuum frame at a distance greater than the diagonal of map to be exposed.
(&) Place map, face down, on a sensitized panchromatic negative in vacuum frame.
(c) Expose black separation by successive exposures through red, green, and blue filters in the approximate ratio of 1, 2, 1 so the total exposure will in development block out all detail on negative except black printing areas.
(J) Develop as for line negatives (par. 47). Complete blocking out is not obtained, but other color details are sufficiently fogged so they do not print up in subsequent exposure of the press plate.
Note. If original map quality is poor and insufficient contrast is obtained, a satisfactory negative can usually be prepared by contact printing a positive and then making a final contact negative from the positive.
54
(e) Expose preliminary blue color-separation negative by placing map face down on a panchromatic film and exposing through green and red filters in approximate ratio of 2 to i, so total exposure blocks out all colors except blue and black.
(/) Mask out black detail by mounting positive made from black-separation negative in register with blue-separation negative. Expose the two registered negatives to a film in the vacuum frame. Develop to obtain the corrected blue-separation positive.
Note. The positive can be used directly for making glue-or gum-reversal plates, or can be contact printed to provide a negative for albumen plates. If the normal black-separation positive does not completely block out the black-printing lines, a new black positive should be made with a thin sheet of acetate inserted between the black-separation negative and the film using a diffused light source or several lights to undercut and thicken detail on the resulting black positive.
(• Position copyboard and lensboard to ratio of reproduction required.
6. Adjust camera lamps and carbons to obtain uniform light intensity.
i. W ith camera arc lamps on, examine image on ground glass. Center image, check size and focus, and adjust if necessary.
am • MB HI 'V. zS'.H
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f/16 - 15 sec f/16 - 15 sec f/22 - 75 sec
f/45 - 10 sec f/45 - 60 sec f/45 - 150 sec
f/90 - 30 sec (flash)
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2 f/22 - 75 sec f/22 - 55 sec f/16 - 30 sec
f/45 - 300 sec f/45 - 420 sec f/90 - 30 sec (flash)
, f/90 - 65 sec (flash) f/90 - 90 sec (flash)
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f/16 - 30 sec f/16 - 45 sec f/22 - 300 sec
f/45 - 90 sec f/45 - 60 sec f/90 - 90 sec (flash)
f/90 - 30 sec (flash) f/90 - 30 sec (flash)
BASIS: 133-line screen, 13/64" separation (screen surface to negative), 200 ft-candles illumination.
FOR USE:
1. Select illustration corresponding with tone range of copy. Note exposure for each fZ-line.
2. Measure light intensity reflected from white area of copy. Note Weston Exposure Meter reading. Multiply exposures (step 1) by exposure factor. WESTON METER READING 50 75 100 125 150 175 200 225 250 275 300 FOOT-CANDLES
EXPOSURE FACTOR 4 8/3 2 8/5 4/3 8/7 1 8/9 4/5 8/11 2/3 MULTIPLIER
3. Expose on f/-lines for times determined in step 2. Develop 3 minutes at 68 F (photomechanical film developer).
Figure 43. Halftone negative exposure chart.
Note. The halftone negative control chart (fig. 43) pro- Copy to be photographed can be classified by direct com-vides a basis for estimating the exposure times required for parison. Or, a gray scale with a hole punched through correcting different contrasts of copy. The illustrations range each tone step can be used to obtain the tone range of the from flat low-density prints to flat high-density prints. Gray copy by matching the tone steps with the lightest and darkscales alongside indicate the range of tones in each print. est detail on copy.
CHAPTER 5
NEGATIVE CORRECTIONS AND LAY-OUTS
Section I. NEGATIVE CORRECTIONS AND LAY-OUTS
57. General
In. photolithography, all changes, additions, and positioning for lay-outs are made either when preparing the original map copy or in retouching and assembling negatives. The offset printing plate cannot be corrected or changed except for adding or deleting minor details. Exposed characters or subjects cannot be shifted in relation to each other and large-scale alterations cannot be made without injuring the grained surface of the plate. However, satisfactory copy is not always attainable and most corrections must be made on the negatives. 1 hese corrections and additions usually consist of assembling, masking, opaquing, and spotting-out operations. They may also include major changes involving stripping, engraving, and etching the negative. All operations are done on a glass-topped retouching stand or stripping table having uniform nonglaring internal lighting.
58. Characteristics of Satisfactory Negatives Characteristics of a satisfactory negative include correct size, uniform density, exact proportions, sharp definition, adequate opacity of the background, and clarity in transparent areas. These properties must be checked before proceeding with corrections and lay-out because a few minutes of additional treatment in the camera darkroom to correct certain deficiencies frequently eliminates hours of retouching on the negatives. In examining negatives, check that:
a. Coverage. Detail of entire copy appears on negative.
b. Uniformity. Density of negative background, weight of type characters, and drafted detail are uniform over entire negative. (Negatives that show decrease of density towards corners of negatives, thickening or merging of lines and characters, and local or general fog in clear areas should be returned to the camera section and corrected.)
c. Definition. All type matter and map detail are sharply and clearly defined. (Soft edges on
characters result in sharpened or thickened and frequently illegible detail.)
d. Size. Over-all size of map image on the negative agrees with designated dimensions on copy. Check measurements along all sides and across diagonals with a magnifier and a steel rule graduated in hundredths of an inch. Measurements must be within ,oi inch if good register is to be obtained in reproducing a color set. Only limited corrections for size can be made later in plate-making or on the press. Since humidity variations cause size changes by shrinking and stretching the negative base, handle and process all negatives in a color set as a group to obtain good agreement in register even if over-all size cannot be obtained.
59. Splicing and Stripping Negatives
a. Combination Negatives. Combination line and halftone negatives are sometimes produced on the camera by double exposure (with and without the screen) interchanging masking on the copy for each exposure. More frequently, such negatives are prepared by splicing or stripping together the required sections of line and halftone subjects as follows :
(i) Trim line or halftone sections to fit within cutaway openings in larger negative. Then carefully splice in position, joining with strips of red-cellophane self-adhesive tape to back of negatives. Be sure tape does not overlap printing detail. (To correct slight overlapping, cut lightly through tape with razor blade and lift tape.)
(2) Carefully align marginal data and similar text with borders, preferably using dividers or marked strip of paper to check parallelism.
(3) To join inserts or negatives, hold them in accurate relationship, with small padded weights, until splicing is completed.
b. Group Assemblies. To assemble groups of negatives such as four or eight pages for book or manual reproduction, position negatives over previously prepared lay-outs containing marks for locat
59
ing the individual negatives. For color-register combinations either prepare lay-out on a matte topo-base acetate sheeting or use first-color press plate to key other color negatives into register.
c. Strip Pilm. Halftone illustrations can sometimes be stripped in pages of text, or place names in halftone areas of photomosaics, by covering areas of copy with pieces of black paper to provide clear areas on the negative. Proceed as follows:
(i) Expose additional subjects on strip film and process in normal manner. (See par. 48.)
(2) Following final wash, carefully slide strip film off base and place in clear desired area on emulsion side of negative that has first been covered with strip-film adhesive prepared according to instructions accompanying film or as follows:
Gelatin (leaf or granular). % ounce Water (hot)................. 16 fluid ounces
Acetic acid (28 percent) ... 1 fluid ounce
I )issolve gelatin in hot water; then add acetic acid and cool. (Adding a few grains of a preservative such as sodium benzoate prevents deterioration.)
(3) Use small pieces (about 2 by 3 inches) of photographic blotting paper to manipulate and press strip film into contact with negative. Then dry. 11 joining edges of stripped-in areas require opaqu-ing, apply opaque on back side of negative to prevent loosening strip film.
d. Combinations. Stripping is frequently unreliable for repeated use in vacuum frame. Combinations are more effective if enough working margin is available around inserted area. (See a above.) Otherwise expose two negatives (line and halftone) from the same copy. Then, opaque all line areas out of halftone negatives, and all illustrations out of line negatives. Double expose successively in register onto the sensitized press plate. To obtain register, use one of the following methods:
(1) Scribe center marks for locating negatives on press plate (before sensitizing).
(2) Develop center marks of first negative exposed applying small spot of developing ink over each mark, rubbing down, and then bringing marks out with dampened tuft of cotton. Position second negative to these marks and fasten with tabs of tape to prevent shifting until held by vacuum in printing frame.
60. Opaquing
The use of red-cellophane self-adhesive tape together with red, orange, or black paper masks reduces the opaquing required on a negative. Opaquing is
used to spot out pinholes or other markings on negatives, to crop illustrations down to size, and to remove undesired markings or text. Opaquing is usually applied to the emulsion side of the negative. It is applied to the back of negatives having stripfilm additions, or used for two-color separations where opaque must be removed in certain areas to bring out mapping detail for the second color.
a. Types of Opaque. Three types of opaque are included in the reproduction sets.
(1) Water-soluble graphite opaque is best for close opaquing, making corrections, and spotting out pinholes and other defects. Thin applications have high opacity, but may leave stains on the negative when removed from accidently covered areas or from negatives used for two-color separations.
(2) Red opaque is more easily removed without staining the negative, but may be granular and develop pinholes after use in the vacuum frame. It is also used for titles or numbers on the negative.
(3) Turpentine opaque is usually used on glass negatives. It produces a coating that is better resistant to repeated use in the vacuum frame. It is also applied to negatives prepared for two-color Separations because it can be wiped away with cotton dampened in turpentine, carbon tetrachloride, or gasoline without softening the emulsion or dissolving water opaques in adjacent areas.
b. Opaquing Procedure. The opaquing procedure is as follows:
(1) Transfer a small quantity of concentrated opaque to pan or dish, dilute in small stages, and mix with brush until proper working consistency is obtained. To test consistency, apply opaque to margins of negative with brush. If correctly prepared, a single stroke completely opaques area covered. Lumps or ridges indicate insufficient dilution, while thin translucent streaks following brush hairs indicate excessive dilution.
(2) Touch up defects and pinholes with tip of brush.
(3) Opaque areas to borders or outlines by drawing brush so it partly flattens against negative, turning negative to permit opaquing to edge away from operator.
(4) Block out large areas by filling in to outline or marginal opaquing. Use one of the following methods:
(a) Block out with red, orange, or black paper masks. Keep masks at least % inch away from all printing detail to prevent spreading of design resulting from out-of-contact areas.
60
(b) Spread opaque with a %-inch or i-inch flat camel's-hair or sable brush. Use parallel strokes and avoid applying over same area because this develops ridges.
Note. Use an arm board over negative to facilitate opaqu-ing. Also, arrange an overhead light so application of opaque can be observed. Light must be dim enough not to interfere with illumination from the light table.
61. Ruling and Engraving
a. Application, (i) Military grids. Military grids are more accurately prepared and sharply defined by engraving than by photographic reproduction. Although these grids can be engraved directly on the photomosaic or topographic map negative, it is better practice to prepare them on separate pieces of film that can be used repeatedly for all negatives of the same scale. Such grids are prepared either as negatives for obtaining black lines on the map by double exposing to register with exposures on the plate; or as positives for attaching in position on photomosaic negatives to produce white grid lines on the map.
(2) Rule forms and tints. Engraving is similarly preferred in preparing rule forms and parallelline tint negatives because the lines obtained are cleaner-cut than the reproduction of inked lines.
b. Principles. Since the photographic negative consists of an emulsion uniformly deposited on a film or glass base, satisfactory engraving must remove the emulsion cleanly and completely to produce transparent lines. A round or needle point would tear and furrow the emulsion resulting in ragged and broken lines. The engraving tool must remove a continuous shaving of the emulsion and is accordingly shaped similar to a cutting tool used for metal work. It must have a flat sharp-cornered cutting edge the width of lines to be ruled. (See fig- 44-)
c. Procedure. The negative is prepared for engraving by accurately placing tick marks along the margins with a divider, beam compass, or needle point and steel rule. The negative is then squared and taped to the glass top of the light table. The steel T-square or straightedge is carefully aligned to the tick marks, and the cutting tool is then drawn along the edge with a uniform even stroke at a constant angle with the negative. Cutting angle, face, and pressure are first tested by ruling short lines along the margins of the negative and the lines checked with a magnifying glass. Improvised ruling tools can be made from any piece of hard steel such as lithographic needles, a section of a hack-
In /
ttJ
^CUTTING EDGE
Figure 44. Scribing tool.
saw blade, the etching or vaccination pen points, or phonograph voice-recording needles.
d. Miscellaneous Engraving. Negative engraving is also used to touch up defective lettering or symbols on map negatives. Fine line engravings required for illustrations or tints can be prepared on a clear film or glass plate covered with a thin uniform coating of opaque strong enough to interfere with illumination from the light table.
62. Dot Etching
a. General. Dot etching is used to correct tone value or color proportions of halftone positives or negatives in single- or multi-color printing. In mapping, dot etching is principally used for representing contour elevations as layer tints, providing various shades of color in a single printing. Preparing a halftone negative for dot etching requires building up the dot structure so it has a central dense core, with the density of the silver deposit diminishing away from the core to the dot edges. (See fig. 45.) By etching the negative, the diameter of the dot is progressively reduced until the desired value is obtained. Since it is easier to reduce than to enlarge dot sizes, halftone negatives or dot etching are usually “shot high” so only a fine pinpoint opening remains in the high-light areas of the negative. These pinpoint openings are the nucleus for progressive enlargement, increasing in size at etching proceeds.
61
LAYER
TINTS
'APPEARANCE OF DOT ••••• • • • • • • • • • • • . •
RELATIVE DOT SIZE -.002" -.0025" -.003" -.004" .005" +.004" +.0035" + .003" + .0025" +.002"
RELATIVE ETCHING TIME 0 + 1 V2 MIN -pl V2 MIN p-1 V2 MIN + 1 V2 MIN + 1 ’/2 min + 1 ’A MIN + 1 MIN + % MIN + V2 MIN
Figure 45. Dot etching.
b. Procedure. Procedure for dot etching layer
tints follows:
( 1) Prepare copy for exposing negative to be dot etched. Phis consists of a white drawing with black contour lines and contour elevation figures (See fig- 46.)
(2) Expose a “high” negative with a vignetted core by equal exposures through high-light and detail stops (for example, 2 minutes on f/32 line and 2 minutes on f/45 line, plus 2-minute flash exposure at f/90). Develop negative until only pinpoint openings remain between dots. Process as usual by washing, fixing, and final washing. Avoid handling negatives except by edges because fingerprints may
interfere with later acceptance of staging lacquer or etch.
(3) Examine negative against white background or light table with magnifying glass. If a veil appears over pinpoint openings, clear with doublestrength Farmer’s reducer (par. 56/), wash and dry.
(4) Carefully paint out contour areas representing lightest tint (lowest elevation) on finished map with flexible lacquer or lithographic washout solutions. As soon as lacquer is no longer tacky, place negative in tray. Pour in enough freshly mixed double-strength Farmer’s reducer to cover negative. Rock tray to circulate solution for about 1% minutes, remove negative, and immerse in wash
LINE DRAWING
HALFTONE NEGATIVE FOR DOT ETCHING
NEGATIVE ETCHED THEN STAGED WITH ASPHALTUM (FIRST FIVE LAYERS ETCHED AND PAINTED OUT)
NEGATIVE COMPLETELY STAGED ETCHED AND ASPHALTUM REMOVED
Figure 46. Layer tints.
62
tray for i minute. When washed, examine etched dot under magnifying glass. If dot is desired size, dry negative. If dot opening is still too small, return negative to etching bath and continue until dot size is sufficiently enlarged. Then wash and dry.
(5) Paint out next contour-interval area with same lacquer, extending it to meet and overlap previously staged-out area. Let lacquer set as before. Then place negative in tray and again etch with freshly prepared reducer for 1% minutes or longer if found necessary in previous etching operation.
(6) Continue with remaining contour intervals. Reduce etching time for higher elevations as etching progresses more rapidly. (See fig. 46.) After
several such negatives are made and satisfactory reproduction is obtained, negative-making and etching operations can be standardized by controlling time and temperature for exposing, processing, and etching.
(7) When all etching is completed and negative dried, wash off lacquer with a solvent (gasoline or a lacquer solvent). Use solvent sparingly to avoid softening film base. Do not use these inflammable solvents near a flame. Keep only a small quantity on hand. Use safety cans, and provide adequate ventilation.
(8) Check printed appearance of dot-etched negative by exposing on sheet of brownprint paper. 1 f satisfactory, complete final opaquing, retouching, ruling, and engraving of lines and other detail.
Section II. LAY-OUTS
63. General
One of the essentials of good printing is proper lay-out. This is the orderly and pleasing assembly of type matter and pictorial detail on each printed sheet as well as the over-all arrangement of a pamphlet or book. The assembly involves mechanical considerations governing location of subjects, folds, backing, and ink distribution. It also must have good form and balance. Mechanical essentials of lay-out are governed by press limitations of maximum printing area, gripper distance, direction of paper grain, and location of subjects for uniform ink distribution. ( See fig. 47.) In making a layout. an accurate drawing is prepared to full scale showing the location of various subjects on the printed sheet. The copy is then prepared and the negatives are assembled to conform with the layout. Lay-out forms are designated as single, combination. and step-and-repeat (a single subject, a group of different ones, or a multiple of the same subject used to compose the printing area of the press plate). The lay-out can be made directly on the plate, but it is more frequently prepared on a heavy ( 8o-pound) orange masking paper on which the positions for the negatives are marked. The orange paper is then cut away to permit exposure through the printing areas of the negative to the press plate.
64. Lay-out Procedure
The procedure in preparing a lay-out is as follows: a. Select a sheet of masking paper large enough to cover the press plate.
b. Attach masking paper squarely on glass-top layout table with tabs of self-adhesive tape.
c. With a sharp pencil or ruling pen, carefully draw lines indicating vertical center line of plate, gripper distance (corresponding to margin of plate necessary for clamping on press minus distance allowed for gripping paper). Draw center lines of positions for negatives to be used. Prepare combination forms, in reverse direction reading from right to left because assembled negatives will be turned over for exposure on the press plate.
d. Carefully place each negative (emulsion side up) in exact agreement with negative-location center lines on lay-out paper. Attach negatives with tabs of self-adhesive tape.
e. Detach lay-out paper with its assembled negatives from lay-out table. Turn assembly over and switch on lights in table. Using sharp knife or razor blade, cut lightly through masking paper (not through the negative) and remove paper covering printing areas of negative. To keep from cutting paper, place small sheet of clear film between negative and paper.
f. With retouching brush and opaque, spot out all pinholes and defects.
65. Combination and Step-and-Repeat Lay-outs
a. Preparation of combination and step-and-repeat forms follows the sequence given in paragraph 64, except that a number of negatives are assmbled on the lay-out sheet and exposed as one unit. Indi-
63
I------------23------------
r--------2O’/2~---------*1 Fl-----------------------7----
BACK EDGE OF PLATE / ------------------------------------------------------------------------------------- , ........., | | 17 ; % ।-• y /8-।
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AREA | lU ™^ING -22V,—;
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I %" MINIMUM I MARGIN | I 5/16
I Uli 1 ! MINIMUM GRIPPER |
1,/4" minimum margin
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’9"L21?"OFFSET PRESS \ e 2 op pa J
(MULTIUTH 2066) 20//x221/a// OFFSET PRESS
(HARRIS LTE) p---------------28%---------------p
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jS J MAXIMUM „
r—----------- PRINTING ----28----•J
04 । AREA
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I I
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MINIMUM GRIPPER 1 1%" MINIMUM MARGIN |
L--------1------1_______L_________■
\------F--------
GRIPPER EDGE ' \ EDGE OF PAPER
22" x 29" OFFSET PRESS (ATF—WEBENDORFER)
Figure 47. Press-plate lay-outs.
vidual negatives must be equally transparent in the clear areas to obtain a uniform printing plate.
b. Step-and-repeat forms are frequently exposed from a single negative, instead of an assembled group of identical negatives, by preparing a lay-out carrying the required number of center lines and openings for the number of exposures to be made.
(1) Attach lay-out in position on press plate.
(2) Mount negative over first opening in lay-out and register to drawn center lines. Mask all other openings for exposure.
(3) Completing first exposure, move negative to second opening, shift masking to cover remainder of
plate. Make second exposure. Repeat until all required prints are exposed on press plate.
Note. In commercial production, step-and-repeat and combination forms are prepared with a photocomposing machine in which the negatives are mounted in holders and accurately exposed to predetermined locations on the press plate.
66. Double Exposure
Double shooting is a term describing the successive exposure of two or more negatives in register over a particular area of the press plate. This combines the printing detail of each negative and avoids the more troublesome stripping operation. To make a
64
WORK TABLE
TABLE | | TABLE | | TABLE | | TABLE |
[GLASS-TOP 1 RETOUCHING
|GLASS-TOP| RETOUCHING
GLASS-TOPI RETOUCHING
LASS-TOP] RETOUCHING
PAPER-CUTTER TABLE
REAR TRUCK-BODY EXTENSION
BLACKOUT CURTAINS
ENTRY DOOR
STEPS
FOLDING FIELD TABLE
Figure 48. Map lay-out section.
single-color map plate, successively expose the first negative carrying the line work, the second adding place names and marginal data, and the third adding tint areas representing woods, contours, or bodies of water. Negatives must have identical scale. Registration between them is obtained either by positioning each to engraved center marks on the plate, or by developing the center marks of the first exposure on press plate to guide positioning the others.
67. Color-register Lay-outs
ci. Single-color Map. Lay-outs for printing a single-color map are best prepared on the press plate. Scribe center and gripper-edge marks along gripper margin for positioning negative on plate. Secure negative in register to these marks with tabs of self-adhesive tape, and add masking. Expose and process plate in normal manner. (These same gripper-edge marks will be used to align press plate to corresponding indicating marks on plate cylinder.) Gripper marks must extend to edges of plate and be long enough to reach corner marks of map. A convenient way to locate them is to use strip of metal as a template. Cut template to width of gripper margin, and superimpose flush with edge of plate to guide scribing tool.
b. Step-and-repeat forms. Lay-outs for color register of step-and-repeat or combination forms are more difficult to prepare because paper or acetate sheeting does not maintain accurate dimensions. The following methods can be used :
( 1 ) With combination subjects, assemble and expose first-color negatives to obtain first-color press plate. Following normal development and processing, use this press plate as a key for assembling negatives for each successive color plate. Align each negative to center marks, checking registration with magnifying glass, and join them together with strips of self-adhesive tape. Be careful that waves or buckles do not form because they displace relative positions of subjects.
(2) A sheet of glass, vinylite, or topo-base acetate film is used for accurately preparing the lay-out. Draw center-mark locations for subjects directly on glass or plastic, or on small tabs of transparent self-adhesive tape affixed to surface. Attach negatives to this lay-out with tape tabs and mask out remaining areas with strips of opaque paper.
(3) Coat glass or low-shrink-matte plastic base with an albumen or deep-etch sensitizer in a whirler and expose to negatives assembled for first color. Processing is similar to that for a press plate. Use light blue or methyl violet dye instead of developing ink. Carefully develop with water and a cotton swab and dry. Light blue or violet image formed is the key lay-out on which each of the subsequent groups of color-separation negatives is assembled and secured.
68. Color Proofs
Proofs for judging color register between the detail of a multicolor map are used to check errors and progress without waiting until plates are made and
65
run on the press. The following methods are used for obtaining advance proofs.
a. Brownprints. Successively expose the colorseparation negatives in register on a sheet of brownprint paper (hold paper in contact with the negatives in a vacuum frame). Expose each negative for a different length of time to identify color separations by different shades of brown. Since exposure of brownprint paper to an arc lamp produces a visible image, no further processing is necessary.
b. Multiple Exposures. Sensitize a metalmounted paper sheet or a press plate with standard albumen coating. Register and expose each negative in succession, to scribed marks or to center marks developed from exposure of first negative. Cover plate with developing ink or roll up with an offset ink, dust with French chalk, develop in normal manner, and dry. This produces a composite print of all negatives. A colored proof can be obtained by mixing small quantities of pigments or dyes into
separate batches of albumen sensitizer corresponding to required reproduction colors. First, sensitize mounted board or metal plate with one of colored coatings and expose through corresponding colorseparation negative. Following exposure, develop plate with water, sensitize with next colored sensitizer, expose through separation representing that color, and develop again. Repeat this operation for other colors until complete composite proof of all color separations is obtained.
c. Color Paper. Color paper can be used to obtain full-color proofs from a set of map color-separation negatives without making plates or operating the press. Proofs are made by using colored lights to successively expose the paper through the negatives. These lights correspond to the desired printing color for each separation. Issue of color paper and processing kits with instructions is limited because additional facilities and controls are required.
66
CHAPTER 6
PLATE GRAINING
Section I. EQUIPMENT
69. General
The photolithographic plate is usually a zinc or aluminum plate whose surface is prepared with a grained or matte finish. This surface is both ink-and water-receptive and has a good “tooth” to which the albumen image will adhere. The grain must be deep enough to carry necessary moisture throughout the press run and fine enough to retain clean-cut edges on small halftone dots or line detail. The most satisfactory way to prepare the plate surface for lithographic printing is by use of the plate-graining machine.
70. Plate-graining Equipment
a. General. The plate-graining machine (fig. 49) consists of a stand supporting a heavy power-driven oscillating tub. Plates are placed in the tub, secured, and then covered with graining marbles and an abrasive. The tray is set in an eccentric motion so the marbles roll in small circles to gradually grind the abrasive material into the surface of the press plates. The size and type of marbles used, the nature of the abrasive material, and the time allowed for graining determine the kind of grain obtained. Marbles that are too light
GATE HANDLE f CLAMP PLATE clamp
CROSS BAR | JjF
M BL
H- —---------------------1
M . - ■ GRAINER : |»
TUB ..... . k_ -----“T---~F7—, M
| . -rr * -W ■■■■
MECHANICAL '..-- IB !
JACK —-n _________________ ................. ........
I BBBHI OBrtCLUW”—JIf 85
f TS . / 1 \
Wm ywpi j/J- s Au Brgfe* ' L t\
5 Skf ’ ' marble
Wh VfiSI dump
J ; AND
X ■ BASKET
Z ■' ''' holder
—acsL*** **-*-*»4llwvy'. ‘
Figure 49. Plate grainer.
67
SATISFACTORY
(UNIFORM, FINE, DEEP GRAIN)
UNSATISFACTORY
(SHALLOW, FLAT, SCRATCHY GRAIN)
Figure 50. Plate grains (enlargements)
or too heavy produce a shallow grain. Light marbles lack weight to force the abrasive into the plate while heavy ones break up the abrasive. Too little water makes a paste of the abrasive that is injurious to itself and to the marbles. Too much water floats the abrasive, allowing marbles to slide and scratch the plate. Too slow a speed of oscillation does not let the marbles grind the abrasive into the plate. Too fast a speed causes skidding, wearing flats in the marbles, and scratching the plate. A balanced condition between all these factors is therefore essential to obtain a satisfactorily grained plate. (See fig. 50.)
b. Graining Marbles and Abrasive. Graining marbles are made of steel, glass, porcelain, and wood in diameters from Fs to 1 inch. The usual
abrasive materials are flint, quartz, sand, aluminum oxide, carborundum, and emery in various degrees of coarseness. Steel marbles with an aluminum oxide abrasive are standard field issue because they are best for the zinc plates used in map reproduction.
c. Equipment Location. The plate-graining machine is always located at some distance from other equipment because particles of abrasive used can seriously damage equipment by working info bearings and moving parts. For the same reason, the plate-graining machine must be frequently cleaned and lubricated to prevent rapid deterioration. For maintenance, operation, service, and repair of the plate-graining machine, see TM 5-4420.
(T i__________________ _______Htl J
PLATE-DRYlNGl^N2JLNlkS^Ullt!X__4-J|LZAlE_LA_Cg| (, ’ 1 _
CABINET I ( ENTRY # "nT
er^nAf^D TRISODIUM I DOOR / STEPS
STORAGE BIN PHOSPHATE BIN II
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PLATE-GRAINING curtaVnS " EXTENSION
SINK MACHINE CURTAINS 4
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MARBLE \
WORK BIN i FOLDING
IX I ______________________ ; FIELD TABLE
’ ^SAND BIN । । SAND BIN~| I J-____________
--- ।------—I ~F-~: 7 ~ I =4
Figure 51. Plate-grainer section.
68
Section II. GRAINING PROCEDURE
71. Machine Graining
Zinc press plates issued to map reproduction units usually are grained. They must be stored in a dry place and carefully handled to avoid kinking, damage, or soiling. After use. if no longer needed for a particular job, press plates are regrained and used again. Regraining is as follows :
a. Clean and lubricate plate-graining machine before starting operation. If marbles are rusted, place them in graining machine on some discarded plates; add abrasive, trisodium phosphate, and water; and run machine until rust is removed. Then, wash marbles and machine thoroughly to remove rust particles.
b. Straighten bent edges of plate, using steel hand roller or mallet. If plate shows severe oxidation or is seriously injured, discard it. ,
c. To remove any remaining ink from plate, pour small pool of turpentine or gasoline on center; then, quickly spread over surface and wipe with rag ball. Provide adequate ventilation. Keep away from flame or heating equipment.
d. To remove gum coating, place plate in sink, and wash thoroughly with water and scrubbing brush. Drain and place wet plate, with grained side up. on bed of graining machine.
Note. If two plates are being grained, remove ink from both and wash plates successively with water so first does not dry before second is ready for grainer.
c. Clamp plate to bed of graining machine.
4. Carefullv pour enough steel marbles on plate to cover with slightly more than one layer.
Caution.* Do not drop marbles on plate, fl o avoid denting surface, temporarily place section of a rubber blanket on plate and pour marbles on blanket.
cj. Weigh out /2 pound of aluminum oxide abrasive. Pour it in measuring cup, and mark cup so future weighing is unnecessary. Scatter abrasive over marbles. Dissolve i ounce of trisodium phosphate in I quart of water. Mark small measuring cup to indicate this quantity. Then, sprinkle marbles with solution.
Note. Quantities of abrasive and phosphate are based on 10-square-foot grainer area. For other size grainers, use amounts in proportion. Use just enough water so abrasive adheres to marbles as a thin film.
h. Start graining machine, and continue graining operation for 20 to 30 minutes, depending on
whether plate is new or used and on nature of grain desired. Increased grainings times are ordinarily required when quartz or sand are used instead of aluminum oxide. A second sprinkling of abrasive added 5 minutes before completing the process may be necessary to assure a uniform fine deep grain.
i. Release gate of grainer, jack up tub, and let marbles roll into baskets in marble dump while grainer is in motion. Stop grainer, remove press plate, place in sink, and wash well with water. Use clean scrubbing brush, reserved for this purpose, to remove remaining abrasive material in grain of plate.
j. Drain plate, wipe off excess moisture along edges with clean damp rag, and dry quickly with electric fan or place in drying cabinet. Slow drying seriously oxidizes grained surface. Avoid temperatures above 250° F., because they permanently soften the metal. If climate is excessively damp or cold so moisture condenses on plate, or if plate is to be stored for several weeks, gum or treat plate immediately after washing to prevent oxidation. (See par. 73.)
k. W7ash out grainer before graining another batch of plates.
I. After all plates are grained and grainer and marbles are cleaned, marbles in their baskets are placed in storage bins and fanned dry to prevent rusting.
72. Chemical Regraining
Chemical regraining is used to recondition plates suitable for use when normal graining facilities are inoperative. Prepare strong lye (10 percent caustic soda solution mixed half and half with alcohol) or commercial bleaching solution (such as Chlorox or similar 5 percent sodium hypochlorite mixture) and place in covered tray or tank. Submerge plate for about 20 to 30 minutes. Remove plate and scrub thoroughly with brush and water. Dry rapidly. Wear rubber gloves when handling plates, and provide adequate ventilation when using bleaching solutions.
73. Preventing Plate Oxidation
Zinc oxidizes rapidly upon exposure to moisture, and plates stored in a damp place may become seriously corroded in a few days and unsuitable for re-use. If warm and dry storage conditions are not available, plates must be treated to protect them. Protection consists of gumming plates for prolonged
69
storage under moderately dry environments, etching and gumming for less favorable climates, and treating the plate with chromate for extreme conditions.
a. Gumming Plate. Procedure for gumming plate is as follows: Immediately after graining and washing, place plate on a dry table. Pour small pool of gum arabic solution (par. 87a?) on plate, spread uniformly, and rub down smoothly with damp rag. Fan dry.
b. Etching and Gumming Plate. Procedure for etching and gumming plates is identical to that used in processing albumen plate after development. (See par. 796m.)
c. Chromate Treatment. The Chromate treatment for preventing oxidation of zinc is a patented process.
(1) To prepare chromate solution:
Ammonium bichromate. . 23 ounces
Water .................. 1 gallon
Sulphuric acid ......... 1% fluid ounces
Dissolve bichromate in water (267 ounces of sodium bichromate are equivalent to 23 ounces of ammonium bichromate). Then pour sulphuric acid slowly into solution. Place in enameled or stainless-steel tray or tank. Chromate solutions are toxic.
Wear rubber gloves and aprons when handling plates. Wash hands and arms following contact with chromate solution.
(2) Immediately after graining and washing, immerse plate in chromate solution for about 20 seconds until plate has a medium brown color. Remove plate and drain off excess solution for about 30 seconds. Flush plate with water until water is clear, then fan dry.
Note. Chromate solution becomes depleted with continued use (from six to nine 22- by 29-inch plates or equivalent) as shown by decreased coloration of plate. To replenish, add M ounce sulphuric acid to 1 gallon solution. The solution can be replenished twice, and is then discarded.
d. Storage Precautions. All plates, regardless of treatment, must be kept as dry as possible. Interleaving the plates with acid-free inert paper helps prevent surface scratches and other injuries when packaging. However, since paper is hygroscopic, it absorbs moisture and eventually oxidizes the plate. For long storage under damp or cold conditions, plates can be packaged in groups of 25 or 50 in sealed waterproof containers, placing a mesh bag of silica gel or similar moisture-absorbing material in each container. Bag must not contact plate. Then seal containers.
Table XI. Plate-graining difficulties.
Difficulty Cause Correction
1. Graining shallow or too fine. a. Poor abrasive. b. Too much water. c. Too long graining. If satisfactory abrasive is unobtainable, add fresh batches of abrasive once or twice during operation. Reduce water. Prolonged graining breaks down abrasive. If normal graining period is insufficient, add second batch of abrasive about 5 minutes before end of graining period.
2. Grained surface scratchy. a. Too much water. b. Too fast operation. c. Dragging plates. Marbles slide. Reduce water so it just forms a film of abrasive over marbles. Marbles slide. Reduce speed until scratches no longer appear. Do not drag plates from under marbles or slide marbles off plate after completing graining. Allow marbles to roll off while grainer is running.
3. Round spots on plates. a. Leaving marbles rest on plate after graining. Starts local oxidation. If slight, later counteretching will remove. If severe, regrain plate.
70
Table XI. Plate-graining difficulties—Concluded
Difficulty Cause
4. Graining nonuniform. a. Grainer not level. b. Insufficient abrasive.
5. Old work remains on plate. a. Deep-etch plates. b. Dried ink.
6. Spots and pits remain on plate. a. Hate oxidized. b. Lead spots. c. Electrolytic action.
7. Streaks in drying. a. Hanging plates wet.
8. Plate soft. a. Excessive heat. b. Poor zinc.
Correction
Abrasive, water, and marbles concentrate on low side. Level grainer bed accurately.
Not enough abrasive to spread over plates. Add more abrasive, distributing it over entire bed of machine.
Can only be removed by prolonged or double regraining.
Remove ink by washing with solvent for graining. Wear rubber gloves. If condition is severe, immerse plate in 5 percent caustic soda solution for about H hour; then, wash and grain.
if not excessive, prolonged graining removes oxide spots.
Caused by lead or other metals being rolled into plate in manufacture, usually on one side of plate only. Grain other side and mark defective side.
Specks of iron or other metals, either rolled into plate in manufacture or allowed to rest on the plate while damp, etch holes by electrolytic action. If holes take ink, grain other side and mark defective side.
Due to water running and drying slowly on plate. Drain and sponge or squeegee plate off. Then dry rapidly.
Drying or storing plates above 250“ F., removes spring from metal. No field cure. Avoid excessive heat.
Plates made of pure zinc or zinc containing too large a percentage of lead or other metals ar soft and lose grain rapidly on press. No cure.
Table XII. Check list of plate-graining operations.
1. Clean and lubricate graining machine.
2. Wash ink off plates with turpentine or gasoline.
3. Place plate in sink and scrub well with brush and water.
4. Mount plates on bed of graining machine.
5. Carefully pour enough marbles over plates to cover bed of machine.
6. Sprinkle required quantity of abrasive over marbles and corresponding amount of water (with trisodium phosphate added).
7. Start machine and grain plates for required time.
8. Tilt grainer to remove marbles from plate while machine is running.
9. Remove plate and place in sink.
10. Wash plate with clean brush and water to remove abrasive from grain.
11. Drain plate and dry quickly with fan or in drying cabinet. If plate is not to be used for some time, or if storage conditions contribute to oxidation, apply protective treatment.
12. Interleave finished plates with clean acid-free inert paper and store in dry place.
71
CHAPTER 7
PLATE PROCESSING
Section I. EQUIPMENT AND MATERIALS
74. General
a. The processing of offset press plates includes all operation;-- required to convert the grained metal plate into the finished lithographic printing plate. The offset press plate is a planographic plate that depends on the mutual repulsion between water and grease to define its printing design. This printing design must be a clean-cut greasy image of the map that will be reproduced on the sheet of paper. A satisfactory press plate must retain the printing design throughout the required run on the press without loss of detail, without thickening or sharpening of characters or halftone dots, and without attracting ink on the nonprinting areas to tint the paper background. The subject matter on the offset printing plate must read correctly, that is, from left to right, exactly as it will appear on the printed sheet.
b. Equipment used in processing offset lithographic plates consists essentially of a sink or trough for cleaning and developing the plate; a coating machine for sensitizing the plate surface; a lay-out table for preparing and assembling negatives; a vacuum printing frame with an arc lamp for mak
ing the exposure; and several tables for inking, gumming, or adding hand work to the plate. (See 52-)
75. Plate Whirler
The plate-coating machine, or whirler, is used to apply a uniform coating of sensitizing solution on the press plate. It consists of a revolving-plate supporting bed contained in a housing. The bed can be rotated between 30 and 90 revolutions per minute (rpm). Electrical heating units and an air circulating system are normally included to assist in drying the sensitized coating. (See fig. 53.)
a. Coating Requirements. Since the lightsensitive coating applied to the press plate is the foundation of the printing design, it must be applied in as thin a layer as can be processed. A thick coating is subject to mechanical injury and absorbs water and other chemicals on the press This results in loss of its attracting properties and in erosion or “walking away’’ of the printing design. Uneven coatings, dust specks, or bubbles also result in defective printing areas.
b. Whirler Maintenance. As the plate-
I 4 -I “ ; entry /
1 vaciiii** ! < WORK TABLE DOOR //
I VACUUM ijj : \ STEPS
1 PRINTING । x : /ill
1 FRAME * j ''^/ ,111.,
1 ' : " —
1 I
1-------------1 BLACKOUT I,
CURTAINS > TRUCK-BODY
__________ ARC LAMP \ 1 ' EXTENSION ^-|--|>£< (BELOW) X. 1
/ \ 1 i/^\ .......
/ \l r \ 1 ,______________<
I 1 1 1 ----- ——!
, j 1 PRESS-PLATE pgi r>ii\ic'
\ ’ 1 DEVELOPING GLASS-TOP :.
\ WHIRLER / $|NK TABLE LAYOUT FIELD TABLE
\ / TABLE ______________________
Jr-.... ZT-— I __________________I--------------J r-V.............................. j
Figure 52. Plate-processing section.
72
Figure 53. Sensitizing plate in whirler.
crating mach'ne is exposed to water and chemical solutions, proper lubrication and care are required to prevent rusting and freezing of its bearings. The interior of the tank must be kept clean by thoroughly
washing with water at the conclusion of each day of operation. Sensitizer on the interior of the tank may scale off and spot the coating on the press plate. For complete instructions on operation and maintenance, see TM 5-6044.
76. Vacuum Printing Frame
The vacuum printing frame holds the negative and the press plate closely together for exposure to the arc lamp. Good contact between the negative and plate is required to prevent light from undercutting the opaque areas of the negative and spreading or thickening printing detail. The vacuum printing frame consists of two frames, supported on a stand, hinged so they can be separated or brought together as required. The upper frame carries a plate of clear glass, and the lower has a rubber blanket bordered by a rubber sealing ring. The blanket contains an outlet fitting connected through a rubber hose to the vacuum pump. (See fig. 54.)
MASKING PAPER
/1 I ■ ’
(7 VACUUM PUMP
J AND MOTOR
7 // NEGATIVE \
f VACUUM PRINTING
FRAME
F PRINTING ARC LAMP
Figure 54. Exposing press plate.
73
ci. Operation. To operate the vacuum printing frame, place sensitized press plate on bed of lower frame. Then, place negative with mask (opaque paper border or lay-out sheet) in position on plate and lock two frames together. Turn on vacuum pump to remove air between frames, and bring the press plate and negative into contact. Tilt frame in vertical position for exposure. Following exposure, reverse operations. Lower frame in horizontal position, release vacuum valve, and open frame to remove the negative and plate.
b. Maintenance. The vacuum frame requires little attention other than keeping it clean and lubricating the vacuum pump and motor. Clean glass using a soft rag and carbon tetrachloride or a solution of Aerosol (J4 ounce to i gallon water). Do not use razor blades or other scraping materials because resulting scratches will imprint on the press
plate. For operation and maintenance details, see TM 5-6042.
c. Pressure. The maximum pressure obtained with a vacuum frame is approximately 30 inches of mercury (dial reading), corresponding to about 15 pounds per square inch (psi). This represents a total pressure between the blanket and the plate glass in a 24- by 26-inch vacuum frame of about 5 tons. When a glass negative is used, particles of dirt or heavy masking between negative and vacuum-frame glass under this pressure may break the glass. On the other hand 15 psi is not enough to flatten kinks in press plates or to force the plate into complete contact with a negative that has heavy masking. Therefore, masking must be as thin as possible. In normal operation, about 20 inches of vacuum (10 psi) is used because it provides adequate contact pressure without taxing the vacuum pump.
Section II. PLATE MAKING
77. General
The albumen or direct process of photolithography is largely used for preparing offset press plates in the field because of its comparative simplicity. Better quality printing plates can be produced by deepetch or other methods, but additional time and materials are required.
78. Preparing Plate-processing Solutions Sensitizers for albumen and deep-etch processes are organic colloids, and are affected by temperature, humidity, impurities, light, degree of acidity or alkalinity, and bacterial and fungus growths. Cleanliness and controlled preparation and processing are essential to successful plate making. Sensitizers and most plate etches contain chromates which may cause dermatitis. Wear rubber gloves. Wash and dry hands and arms if contacted by chromate solution. Use salves for dry or chapped skin.
79. Albumen Process
Materials required for the albumen process are counter-etch for cleaning the plate, albumen sensitizer, developing ink, solutions to assist development, plate etch, gum. and washout solutions. Developing ink and washout solutions are furnished ready-mixed. Procedure for albumen plate-making is as follows:
a. Prepare solutions to counter-etch, sensitize, develop, gum. and etch press plate. (See formulas, par. 87.)
b. Counter-etch press plate as follows: Place
plate in sink, flush with water, and scrub with brush. Then, pour about 4 ounces of counter-etch solution over plate, spread quickly, and scrub evenly for about 1 minute. Finally, wash plate thoroughly, first using scrubbing brush and then flushing with clean water. Keep plate wet until ready for coating operation.
c. Prepare quart graduate of water for washing, and put about 4 ounces of sensitizing solution in pouring container before coating operation. Carefully flow sensitizing solution into pouring container through cheesecloth so air bubbles are not transferred. Then, remove press plate from sink, and mount centrally in whirler. Start whirler revolving at about 35 rpm and pour quart of water on plate to flush off any accumulated dust. When most of water is thrown off plate, and only a few drops drip from corners, pour sensitizing solution in steady stream beginning at center of plate. Continue pouring so solution spirals outward until expanding circle of solution reaches edges of plate. Then, increase speed to 60 rpm, turn on heat, close whirler lid carefully to avoid shaking dust on plate, and let spin until plate is thoroughly dry (about 7 to 10 minutes).
Caution: Plate is now sensitized. Carry out following operations, up to development step, in subdued or amber light.
cl. Remove plate from whirler, wipe remaining drops of solution from back with dry rag. Place plate, sensitized side up, on bed of vacuum printing frame.
74
SENSITIVITY OF A X \
BICHROMATED \ \
ALBUMEN \ I RADIATION FROM WHITE
x. | / X FLAME-CORED CARBON
- ■ —VI----------------------------------
/ v
I \
A
TRANSMITTED BY GLASS \\\\\\
—;,W„A---------------------------------------------
/ region
3,000 4,000 5,000 6,000
LIGHT SPECTRUM (ANGSTROM UNITS)
Figure 55. Sensitivity of albumen coating to light.
e. Place prepared negative and attached mask on press plate so emulsion side contacts plate. Locate negative accurately to gripper edge of plate, with aid of reference marks on mask or plate.
f. Clean vacuum-frame glass again, using soft rag and moisture or solvent. Then, close frame and turn vacuum switch on. When dial reaches 20 inches of vacuum, tip frame in exposure position. Increase pressure if necessary because of thick-masking. Reduce pressure to about io or 12 inches when glass negatives are used. When glass negatives are exposed on press plates, fill in areas of plate not covered by negative with strips of card board having same thickness as glass to avoid embossing plate.
g. Position arc lamp centrally in front of and facing vacuum printing frame. Locate so carbons are about 4 feet from surface of glass. For large plates, increase distance to amount greater than diagonal of plate. Mark floor under center of arclamp stand to locate for future plates. Check that
carbons meet centrally. Spread the arms and make sure carbon tips separate at least 1% inches. Do not look directly at arcs. The intense light may cause serious eye injury.
h. Before making first plate, determine necessary exposure time as follows:
(1) Print small negative, containing fine-line or halftone work, with progressively increasing exposures in six or eight positions on press plate. Mark out unused part of plate and start with i%-minute exposure for first print. Then increase exposure time on each successive location by % minute. Shift masking each time until six or eight prints are made on plate. Develop plate and examine under magnifying glass. If exposure time is correct, dot or line detail size is equal to corresponding detail in negative. If entire plate develops out too easily in unexposed areas, coating is too thick. Coat new plate and increase coating speed to 65 or 70 rpm as required. If development in unexposed areas is difficult and requires prolonged
75
soaking in water and addition of ammonia, too thin a coating or excessive heat or light fog is usually the cause. Correct condition or resensitize, using slower coating speed. A correctly coated and exposed albumen plate does not develop too easily. It requires some soaking and sometimes addition of sodium bicarbonate solution for halftones or fine-line areas.
(2) Having determined correct exposure time, note and tabulate the corresponding percentage of relative humidity adding similar information at other times to build up a table similar to the following:
Relative humidity Relative exposure time
Percent Mi 1. Sec.
20 6 0
30 4 0
40 3 0
50 2 24
GO 2 0
70 1 42
80 1 30
90 1 20
(3) If a dial-type hygrometer is provided, mark exposures corresponding to various percentages of relative humidities on a paper attached to face so indicator always points to correct exposure time. (See fig. 56.)
i. Tilt the vacuum frame in horizontal position. Open air escape valve so back pressure does not develop in pump forcing oil into vacuum line. Then
Figure j6. Hygrometer exposure-control dial.
stop vacuum pump. Remove negative and press plate from vacuum frame. Return negative to its container. Place press plate on dry table for applying developing ink.
j. Pour small pool (about 2 inches in diameter) of developing ink on center of plate. Using dry rag ball, quickly distribute ink uniformly over plate, and rub down evenly and smoothly with another dry rag ball. Fan plate dry for about 1 minute. If developing ink is too thick, because of evaporation of solvent, and cannot be applied smoothly, dilute with small quantity of turpentine. Keep developing ink rags in covered can for re-use. Discard all waste ink- and turpentine-soaked rags in metal safety cans. The cans must be emptied daily because spontaneous combustion may result from an accumulation of ink rags.
k. Plug sink drain or use tray, and cover bottom with about 1 inch of water. Place inked and dried plate in water and soak for 1 or 2 minutes until swab of cotton rubbed lightly in a circle starts to develop image. Turn cotton as development progresses and unfold to present new surface as cotton collects ink, until entire plate is developed out clean. A short circular stroke without pressure and continued progressively over surface of plate is best. Examine plate with magnifying glass. If shadow tints of halftones, or strokes of characters in fine-line work, join together, dip cotton in sodium bicarbonate solution to open up detail. Drain water out of sink or tray, if necessary, to avoid excessive dilution of bicarbonate solution. If sodium bicarbonate solution is not wholly effective, use solution of ammonia (1 fluid ounce to 1 quart of water) sparingly on cotton to complete development. Difficult development indicates overexposure: light fog indicates too thin, or too old a coating, or a poor negative. Correct cause when making next plate. After developing, flush with clean water and drain or squeegee plate.
I. While plate is still damp, applv plate etch to surface with camel’s-hair etching brush. Circulate etching solution quickly and uniformly with horizontal and vertical strokes. Continue spreading for about 1 minute or longer if development was difficult. Then, flush again with water, squeegee off, and remove plate to dry table.
m. Pour a small pool (about 2 inches in diameter) of gum-arabic solution on center of plate. Using damp rag ball, spread gum over press plate in both directions. Then, turn rag and rub down smoothly so thin even coating of gum covers plate. Fan plate dry. If gum streaks appear across printing area,
76
gum is not rubbed down uniformly and thin enough. Rub down entire plate again with damp rag ball. Plate is now ready for press if it is to be used immediately.
n. If plate is not to be used for a day or more, or if it is required for some other color than black, wash out plate with asphaltum or washout solution. Washout is required because some developing inks contain driers and lose their affinity for the offset printing ink. This is done as follows:
( i ) Place plate face upward on dry table, and pour small quantity of turpentine on center. Using dry rag ball, spread turpentine over plate to dissolve developing ink. Wipe plate clean and dry with rag. making certain no developing ink remains on plate.
(2) Pour small pool (2 inches in diameter) of asphaltum or washout solution on plate. Add a little turpentine if asphaltum appears thicker than developing ink previously used. Using dry area on rag ball, spread solution over plate and rub down smoothly and evenly. Plate can now be stored indefinitely if kept in dry place.
80. Hand-drawn Additions to Albumen
Plates
a. General. W hen hand work, such as painting in solid printing areas or ruling lines with tusche, is to be added to albumen plate, normal plate procedure is followed except counter-etch for handdrawn plates (par. 87^) is used instead of the regular plate etch. Distribute counter-etch over surface for about i minute with brush or wad of cotton. I hen flush well with water and dry quickly under a fan. Since plate is sensitive to grease, avoid fingerprints or other marks within printing area. Additions or corrections can now be made.
b. 1 l'SCHing Press Plates. Tusching is the process of greasing the printing areas of the plate by hand. The greasing liquid consists of an emulsified grease or diluted ink that can be applied with an artist s brush, lithographic pen, or ruling pen. To facilitate drafting, use a board arm rest (fig. 15) or pieces of clean blotter or paper as hand rests. The procedure for tusching follows:
(1) Pour small quantity of tusche in small deep dish.
(2) If applying tusche with brush, paint on in a thin uniform layer, covering area with one stroke where possible. If tusche is too thick to flow properly when using a pen, add water or turpentine, following instructions on bottle. Add only enough
for tusche to flow properly. Excessive thinning causes tusche to spread on plate. Try tusche on gripper or back edge of plate before drawing in work areas.
(3) If using water-emulsion tusche, dry for 1 hour or longer before finishing plates. If developing ink or transfer ink thinned with turpentine is used, additional time is not required.
(4) After tusche dries on plate, dust with French chalk (talcum powd&r), using tuft of clean dry cotton for applying chalk. Do not rub, because this spreads tusche into adjoining areas.
(5) Then, place plate in sink. Apply plate etch with camel’s-hair brush, using light strokes in both directions to distribute etch evenly. Continue etching operation for about 1 minute.
(6) Flush off etch with water, drain plate, and place on table.
(7) Pour small pool of gum on center of plate. Spread and rub down thin with damp rag ball, and fan dry.
(8) Finally, wash out plate with turpentine and thin coating of prepared washout solution. Plate is now ready for press, or can be stored in dry place until needed.
81. Carbon-paper Tracings
Press plates for overprinting are frequently prepared by transferring the additional data drawn on the map directly to the plate through an intermediate sheet of carbon paper placed between the map and plate. A lithographic carbon paper is used, but if unavailable the standard typewriter carbon paper is satisfactory. The procedure is as follows:
a. Wash press plate and apply counter-etch for hand-drawn plates (par. 87b), flush with water, and dry rapidly under fan. Since plate is now sensitive to grease, handle carefully by its edges.
b. Place carbon paper and attach map in position. Trace outlines and data, taking care that pressure on paper is applied only by stylus or pencil. To transfer data to localized areas of plate, use smaller sheets of carbon paper. Trace corner marks or other reference marks on plates to register the overprint. Add tusche or litho crayon to plate to thicken lines and emphasize necessary detail.
c. To prepare plate for press, apply plate etch, gum thinly, dry, and wash out with turpentine and wash solution. (See par. 79/, m, and n.)
82. Blue Lines (Blueprinting Press Plate)
Blue lines are printed on press plates to provide an
77
outline to which tusching or other hand work can be added in exact register with other color plate or plates made from the same master negative. Ordinarily the master or key negative is the same one used in making the black printing plate by the albumen process. The procedure follows:
a. Clean and counter-etch press plate as in preparing for sensitizing with albumen. (See par. 79.) Keep plate wet until blueprint solution is applied.
b. Place plate centrally in plate-coating machine, and rotate at about 35 rpm.
c. Pour enough mixed blueprint sensitizer (par. 87^7) in center of press plate to cover plate. Then, close coater, turn on heat, and spin until dry.
d. Remove plate from coater, wipe back dry, and place plate on bed of vacuum frame.
e. Locate negative accurately on press plate. Close vacuum frame and apply vacuum as described in paragraph 79/; then tilt vacuum frame in exposure position.
f. Expose plate to arc lamp for about double time used for albumen plates. (See par. 79/7.)
g. Remove plate from vacuum frame, place in sink, flush with water, flow with grease-sensitizing counter-etch, flush thoroughly with water, and dry quickly. Plate is now ready for tusching. Since it is sensitive to grease, handle carefully.
83. Bichroma+ed Gum Coating for Desensitizing Plates
A protective light-hardened bichromated gum coating applied to nonprinting areas of press plate protects the plate from injury during adjustment of press. It also prevents scumming or catching-up, and can be used when plate difficulties are experienced and the additional time involved in its application is available. Bichromated gum coating solution is prepared as described in paragraph S’/h. (See also par. 78.)
a. Apply to press plate instead of regular gum coating after plate is etched. Rub down and dry to form a uniform thin coating free from gum streaks.
b. Expose plate to arc lamp for about the same time as required in making the albumen plate. Do not look at the arcs.
c. Wash under water for 2.or 3 minutes.
d. Finally, gum up with uniform thin coating of gum arabic solution. (See par. 79m.) Scumming of bichromated gum coating indicates overexposure. If this occurs, reduce time exposure to arc lamp.
84. Reversal Plates
Reversal and deep-etch plates are made by tanning the sensitized coatings around the design areas by exposing through a positive or a drafted tracing instead of a negative. Development dissolves the coating in printing areas, permitting areas to be further etched or treated to accept the greasy ink.
85. Glue-reversal Process
The procedure for glue-reversal plate-making is as follows:
a. Counter-etch same as for albumen plates. (See par. 79A)
b. To sensitize with glue sensitizer (par. 88&) mount plate in whirler, rotate at about 35 rpm, then flush with water. When excess water spins off plate, apply sensitizer in steady stream. Begin at center and then spiral outward until plate is covered. Increase speed to 60 rpm, turn on heat, and fan and whirl plate until dry.
c. Remove plate from whirler, wipe back and corners dry, and place on bed of vacuum frame. Place positive or tracing in position on plate, making certain it reads correctly (left to right) as viewed from above. Secure positive to plate with tabs of transparent cellophane tape. No masking is required because exposed coating extends to edges of plate.
d. Expose press plate for about double the time used for albumen plates. (See par. 79/z.) If development and processing thickens characters, plate is underexposed; if it sharpens them, overexposure is indicated. Transparent areas of positives must be clear, without veil or fog. Existence of fog or use of tracing paper or tracing-cloth positives requires increased exposures. Determine increased time experimentally or approximate using light meter. (See fig. 37.)
e. Place plate in tray of water and let water flow over it for 1 minute. Then flow dye solution (par. 88c) over plate, allow to penetrate about 1 minute, flush with water. Then, swab lightly with wad of cotton (using short circular strokes) until entire plate is developed.
f. Flush plate with fresh water, drain quickly, and blot dry with photographic blotting paper, paper toweling, or unsized newsprint paper. Do not shift paper because its re-use may transfer glue to printing areas. Dry plate thoroughly.
g. Touch up all defects and exposed metal in nonprinting areas by applying gum arabic solution (par. 871/) with artist’s brush. Then fan dry.
h. Pour small pool of prepared washout solution
78
or transfer ink diluted with turpentine (to the same consistency as washout solution) on plate. Using rag ball, spread solution over entire plate. Rub down firmly with short circular strokes so solution enters grain of metal. Continue rubbing until coating is dry. If surface remains tacky, dust French chalk over ink and rub down with dry rag.
i. Place plate in tray with enough reversal solution (par. 86a) to cover plate. Soak for minute or two. Then, remove glue stencil surrounding workareas with soft bristled brush, using short circular strokes. Continue until nonprinting areas are clean.
j. Apply plate etch as for albumen plates (par. 79/), but continue spreading etch for about 2 minutes. Then, flush off etch with water, and drain plate.
k. Place plate on dry table and apply gum solution. (See par. 8yd.) Spread and rub down to thin uniform layer. Plate is now ready for press.
86. Gum-reversal or Deep-etch Process
I he procedure for gum processes is similar to that for glue-reversal processes except for changes in sensitizing and processing solutions. The procedure is. as follows:
a. Clean and counter-etch as for albumen plates. (See par. ygb.)
b. Place plate in whirler, rotate at about 35 rpm and pour water over plate. When excess water is thrown off flow sensitizer on plate in steady stream. Begin pouring in center until about half solution is used. Then move container sideways so solution spirals outward to edge of plate. Increase speed to 60 rpm, turn on heat and fan, close lid, and whirl until dry (10 to 20 minutes).
c. Remove plate from whirler, wipe off water and solution on back and corners, and place face up in bed of vacuum frame.
d. Put positive or tracing in correct position on plate, and attach with tabs of transparent cellophane self-adhesive tape. Do not use additional masking unless exposures are to be made on another part of plate.
e. Close vacuum frame, apply vacuum and tilt in exposure position. Expose about twice as long as for albumen plates. (See par. 79/1.)
f. After completing exposure, remove plate from vacuum frame and place on dry table covered with several sheets of paper.
g. Pour pool of developer on center of plate. Using spreader quickly distribute and circulate over rest of plate. Continue circulating for about 3
minutes (until slight frothing in image areas indicates penetration through unexposed coating). Then, squeegee off solution and apply more developer. Spread as before and continue for another 3 minutes. Squeegee excess solution off plate and fan dry.
Note. To make suitable spreader for applying developer and deep-etch solutions, cover bottom of wood block with layer of thick pile rug. Cut rug large enough to spread over sides. Tack rug to block along top edge.
h. For deep-etch only—(1) Wash plate as follows : flow small quantity of anhydrous alcohol on center, spread and wipe with clean rag, and then dry. Touch up all defects and uncoated places in nonprinting areas of plate with gum sensitizer. (See par. 8gb.) Apply sensitizer with artist’s brush in uniform thin layer, and fan dry. Then, expose plate to arc lamp for 6 to 8 minutes to thoroughly light-harden touched-up areas.
(2) Apply deep-etch solution and spread over plate as in developing step but using a spreader kept tor this purpose. Continue circulation for about 1% to 2 minutes. Then squeegee excess solution off plate and fan dry.
i. Wash plate several times as follows: flow small pool of anhydrous alcohol on plate, and spread with clean rags or paper towels. Provide adequate ventilation to remove fumes. Change to new towels or rags for each application, and work solution well into plate to wash out any remaining developer in printing areas. Then blot with dry towels and fan dry. If alcohol is unavailable, clean plate by flushing with running water. Do not rub or use pressure because gum image is easily injured. Then, quickly drain and blot off excess water with photographic blotting paper. Do not shift, rub, or re-use paper because this will transfer gum coating into printing areas. Then fan dry. Printing areas of plate must be thoroughly clean and free from any trace of gum so ink-receptive base will adhere firmly to plate.
/.To touch up defects and uncoated places in nonprinting areas on plate, apply gum arabic solution (par. 8yd) with artist’s brush. Then, fan dry.
k. Apply coating of prepared washout solution or transfer ink diluted with turpentine (to same consistency as washout solution) over plate with rag ball. Spread and rub solution firmly into exposed areas of metal plate, using short circular strokes. Continue rubbing down until coating is dry. If ink-remains tacky, dust surface with French chalk. Spread and rub down with dry rag.
I. Immerse plate in a tray containing reversal solution (par. 89/), and soak for several minutes. Then,
79
remove gum stencil by rubbing with soft bristle brush. Continue rubbing uniformly over entire plate until surface is clean.
m. Flush plate with water, squeegee off excess, and apply plate etch (par. 87c) with etching brush. Circulate etch over plate for about 2 minutes.
n. Squeegee off etch, place plate on dry table, and gum up plate in normal way. Then fan dry. Plate is now ready for press.
87. Albumen Plate-processing Formulas
Chromate salts and solutions may cause dermatitis. Wear rubber gloves. Wash hands if contacted by solutions. Concentrated acetic, nitric, hydrochloric, or phosphoric acid causes skin burns. If contacted accidentally, wash immediately with water and neutralize with bicarbonate of soda solution. Concentrated ammonia also injures skin. If contacted, wash immediately with water and neutralize with weak acetic and solution.
a. Counter-etch.
Acetic acid (glacial) ..... 6 fluid ounces
Water to make.............. 1 gallon
b. Counter-etch (Alternate for Hand-drawn Plates).
Water...................... 1 gallon
Nitric acid ............... 1 fluid ounce
Alum (potassium) .......... 4 ounces
Mix nitric acid in water, then add alum and shake or stir until dissolved.
c. Albumen Sensitizer, (i) Solutions.
Solution A:
Albumen (flake or scale) 3 ounces
Water (to 3.3° Baume)
or ................ 24 fluid ounces
Solution B:
Ammonium bichromate. 1 ounce
Water (to 5.1 ° Baume") or ................... 12 fluid ounces
Solution C:
Ammonium hydroxide. *4 fluid ounce
Water................... 4 fluid ounces
(2) Instructions. Dissolve albumen by tying in cheesecloth bag, suspend in water for several hours or overnight. (See fig. 57.) Do not squeeze insolubles remaining in cheesecloth into solution. If considerable insolubles remain, use larger proportion of albumen so resulting solution has density of 3.30 Baume. Dissolve ammonium bichromate in water by stirring. Add solution A to B. Then add solution C in sufficient quantity to just clear the cloudy appearance, or to a pH of 7.4 to 7.6. Filter mixed
sensitizer through pad of cheesecloth or cotton. Add water, if necessary, to bring specific gravity to 1.029 or 4.10 Baume. Keep sensitizer in cool dark place. Solution can be used within a few hours after mixing, if kept cool is satisfactory for several days. To preserve solution, add 50 grains of sodium benzoate or % ounce of formaline.
k—SUPPORTING . r s jw *---FUNNEL
STRING JF
W WATER 7^--SOLUTION
\ • 7lEVEL —
" 3 It H COTTON
I .//CHEESECLOTH
1 BAG |
' WR ” f/ WITH ALBUMEN | ||
, Il DISSOLVED » ||
7F albumen I gl FILTERING
7 1 lr str,ng
V ’’*7 III SOLUTION
GRADUATE
...I....... K. . ■ . ______
. ..................... .
Figure 57. Dissolving and filtering.
d. Gum-arabic Solution.
Gum arabic (lumps) ..... 1 pound
Water (to 140 Baume) about 32 to 36 fluid ounces
Dissolve gum arabic in water by suspending gum in cheesecloth bag until density of solution reaches 14° Baume. To increase effective life and prevent souring of solution, add preservative such as % ounce formaline or % ounce sodium benzoate to each 64 ounces of gum solution.
c. Plate Etch.
Solution A:
Phosphoric percent)
Water . . .
acid (85
1 fluid ounce
2 fluid ounces
Solution B :
Gum-arabic solution (rf above) ....... 24 fluid ounces
Solution C:
Ammonium bichromate .......... % ounce
Water .............. 2 fluid ounces
Dissolve each solution separately. Then add together and mix. Keep in cool place. Effective for several days or longer until souring occurs.
fi. Sodium Bicarbonate Solution (To Assist Development).
Sodium bicarbonate .... 1 ounce
Water .................. 16 fluid ounces
80
g. Blueprint Solution (For Blueprinting Only ).
Stock A:
Potassium ferricyanide ............. 2 ounces
Water ............. 12 fluid ounces
Stock B:
Citrate of iron and ammonia (green scales) ............. 4 ounces
Water .............. 12 fluid ounces
Note. Keep stock solutions in separate bottles in dark place. Mix equal quantities of stock A and B just before using. One ounce of each mixed together is adequate to coat a plate.
h. Bichromated Gum Protective Coating.
Stock A:
Ammonium bichromate ........... % ounce
Water ............... 8 fluid ounces
Stock B:
Gum-arabic solution
(d above) '....... 16 fluid ounces
Dissolve stock solutions separately. Mix together before use.
No.te. If kept in cool place, solution is effective for several days.
88. Glue-reversal Process Formulas
a. Counter-etch. (Same as par. 86a.) b. Sensitizer.
Solution 1 :
Glue, liquid (photoengravers) ........
Water .............
6 fluid ounces
24 fluid ounces
Solution 2:
Ammonium di-
chromate ........ y4 fluid ounce
Water ............... 6 fluid ounces
Solution 3:
Ammonium hydrox-
ide (28 percent) . . 34 fluid ounce Dissolve each solution separately, add together.
Filter through cotton or cheesecloth before using.
c. Dye Solution.
Methyl violet dye................ % ounce
Water (hot) .................... 16 ounces
Dissolve by adding small quantity of water to dye, rubbing in well to form paste. Gradually add more-water, rubbing and stirring until completely dissolved. Filter through cheesecloth, and cool to room temperature.
d. Reversal Solution. (Same as par. 86a.)
e. Plate Etch. (Same as par. 862.)
f. Gum. (Same as par. 86d.)
89. Gum-reversal and Deep-etch Process Formulas
a. Counter-etch. (Same as par. 86a.)
b. Sensitizer,
Gum - arabic solution
(same as par. 86d) .... 6 fluid ounces
Ammonium bichromate . . 34 ounce
Water .................... 6 fluid ounces
Ammonium hydroxide (28 percent) ............ % fluid ounce
c. Calcium Chloride Solution.
Calcium chloride ......... 5 pounds
Water to density of.....40° Baume
Add water to calcium chloride slowly, stirring and testing until density of 40° Baume has been reached. Add more calcium chloride if density is too low.
d. Developer.
Calcium chloride solution (c above) ...............64 fluid ounces
Lactic acid ............. 2 fluid ounces
e. Deep Etch.
Calcium chloride solution (c above)............... 64 fluid ounces
Hydrochloric acid ....... 2 fluid ounces
f. Reversal Solution.
Citric acid.............. 4 fluid ounces
Water ................... 1 gallon
g. Plate Etch. (Same as par. 86c.)
h. Gum. (Same as par. 86d.)
81
7 able XIII. Plate-making difficulties—Albumen Process.
Difficulty
Cause
Correction
1. Plate does not counter-etch uniformly.
Greasy or oxidized areas.
2. Plate coating not uniform.
a. Greasy areas.
b. Dry areas.
c. C oating thickness not uniform.
d. Rays
e. Comets or flares.
3. Plate does not develop or develops with difficulty.
a. Plate fogged.
b. Coating too thin.
c. Sensitizer too old.
Stronger counter-etch may cut through grease. Or, wearing rubber gloves, scrub lye solution over pate, wash, and then counter-etch. If this does not help, return plate to grainer.
Repels coating. Noticeable chiefly on edges of plate where handled. Handle plate by gripper and back edge only so work area is not affected.
Due to local drying of plate before coating. Keep plate entirely wet with water until solution is applied.
Results from waves in plate, low side on plate support, or nonuniform pouring. Faster coating speed is frequently helpful. To obtain uniform coating, pour solution from center outward in steady stream so it spirals slowly onto plate.
Caused by irregular pouring. Pour solution continuously from center outward so solution spirals on plate.
Caused by bubbles, dirt, or dust on plate or in solution. Wash and scrub plate thoroughly following counter-etching, using filtered water or pouring water through cheesecloth pad. Just before coating, pour quart of filtered or settled water over plate. When applying sensitizer, use freshly filtered solution to remove bubbles and filaments. Pour with spout of container held close to plate so bubbles do not form. Keep interior of coater clean, and wet thoroughly before coating plate to settle dust and dried albumen flakes.
Caused by excessive exposure of plate to room lighting, heat in whirler, or aged too long before using. Work under diffused or amber light. Correct other causes. In an emergency, try to develop out plate by soaking with 3 percent ammonia solution until developing starts. Then, transfer to water. However, forcing development may result in a blind or scummed plate on press.
Usually caused by high humidity, when most of sensitizer spins off before it can set and dry. Also caused by use of too greasy a developing ink that penetrates through coating to metal. Slower coating speed or second application of sensitizer, immediately after first, is helpful. If high humidity and temperature are encountered, use plate etch instead of counter-etch to facilitate development. Assist development with 3 percent bicarbonate of soda or ammonia solution. Bichromated gum coating applied after development and etching may help in continued high humidity.
Effect same as for plate fogged. (See 3a above.)
82
Table XIII. Plate-making difficulties—Albumen Process—Continued
Difficulty
Cause
Correction
4. Plate develops with difficulty in localized areas.
5. Plate develops with difficulty in localized areas.
6. Develops too easily.
7. Halftone shadow dots filled.
a. Negative lacks density or plate is overexposed.
b. Masking inadequate.
a. Out-of-contact areas.
b. Plate coating not uniform.
a. Underexposure.
b. Too thick"a sensitized coating.
a. Negative too thin.
b. Out-of-contact areas.
c. Overexposed.
Partial light hardening because light penetrates through opaque areas of negative. Indicated when surrounding masked area develops more readily. Use prolonged development and assist with sodium bicarbonate or ammonia solution.
Same as for negative lacks density (item 4a). Evidenced by easier development of areas where masking or negative overlap each other. Use more opaque masking paper on next plates.
Especially noticeable in fine-line or halftone work. Caused by insufficient vacuum, thick masking or opaquing close to work areas, lumps of dirt on negative or plate, or kinks or dents in plate. Avoid overlapping masking excessively, and keep masking at least inch away from work areas. Increase vacuum when fine detail is to be obtained from masked negatives, preferably using a single-point source of light. For extreme cases, temporarily blacken reflector and increase exposure time. Out-of-contact areas can sometimes be developed up by local treatment as described in item 3a if they are not too severe.
Correct cause. See item 2 above. Develop further with ammonia or bicarbonate solution in areas that develop with difficulty.
Increase exposure on subsequent plates. An underexposed plate can sometimes be used by carefully developing with cotton, etching, and gumming, followed by baking plate in front of arc lamp for several minutes. However, plate will usually fail on press and must be remade if long press run is required.
While such a plate can be used for short runs, it does not provide full ink density on press. Fine detail or halftones gradually disintegrate (“walk off” plate). Check density of solution. Add water or use faster coating speed for hot and dry atmospheric conditions.
Dots on negative, particularly pinpoint dots, lack enough density to hold back light. A longer flash exposure in making the negative is the usual remedy, although entire negative may require increased exposure or development. Follow procedure for negative lacks density above (item 4a).
Evidenced by localized irregularly defined areas in which shadows are plugged. Use bicarbonate or ammonia solution with further local development to open up shadows.
Same treatment as for negative too thin (item 7a). Do not underexpose plate to compensate for thin negative, or poor printing plate results.
83
Table XIII. Plate-making difficulties—Albumen Process—Continued
Difficulty
7. (Continued).
d. Poor developing ink.
8. Halftone high-light dots miss-
ing.
9. Plate scummed.
Negative fogged or plate underexposed.
a. Pinholesjn negative.
b. Thin negative.
c. Plate scum.
d. Albumen scum.
e. Developing-ink scum.
f. General.
A stringy or long developing ink bridges shadow dots. Although bicarbonate or ammonia solutions help to open up dots, resulting plate may blind or scum. Thin developing ink with turpentine until better ink can be obtained.
High-light dots on negative (pinpoint openings) usually fogged because of halation, overexposure, or other causes. Clearing bath helps negative. Press plate cannot be intensified satisfactorily to bring up partly exposed or missing dots. If time does not permit correcting negative, make new plate and overexpose to “burn” through fogged areas in negative.
Caused by pinholes in negative from dust on copy, copyboard glass, or negative, or from minute gas bubbles in fresh developer. Cleanliness in negative making is necessary to eliminate dust and dirt spots. Slight overexposure or overdevelopment in making line negatives fills in most dust spots, but is not applicable to halftone negatives. Opaquing or spotting out is required if negative scum is to be reduced. Rocking of tray or agitation of film holder in tank development helps eliminate small bubble formation on negatives. See albumen scum for treatment (item 9e below).
Insufficient opacity of negative because of underexposure, underdevelopment, old or cold developer, or other conditions that must be referred to the camera section for correction. Use aids to development. See plate develops with difficulty, item 3 above.
Caused by oxidized spots or pits in plate, or sand or dirt remaining on plate following counteretching and washing. Little can be done for oxide spots and sand spots because plate is greased. If not severe, some spots can be removed by rubbing out with snakeslip and then applying plate etch.
Results from incomplete development when some albumen sensitizer remains in grain and hardens there. If discovered early, apply plate etch for a minute or longer. Then wash with water and gum thinly and uniformly.
Results from too thin an albumen coating or too greasy a developing ink that penetrates through coating and greases metal plate. A strong etch may remove scum. Otherwise discard plate. See coating too thin (item 36 above).
Applying bichromated gum coating to plate is advisable whenever serious scum or similar difficulties are regularly experienced with plates. (See par. 82.)
84
Table XIII. Plate-making difficulties—Albumen Process—Concluded
Difficulty
Cause
Correction
10. Developing ink streaks.
Ink spreads to nonprinting areas.
Insufficient drying of developing-ink coating, or too greasy and slow-drying developing ink plus harsh rubbing-in during development without turning cotton freely or using new cotton, spreads ink to adjoining areas of plate. If only poor ink is available, dry developing-ink coating for several minutes, then dust and rub in French chalk (talcum powder) on developing ink. Then dry for several minutes before development.
Table XIV. Plate-making difficulties—glue-reversal process.
Difficulty Cause Correction
1. Plate not uniformly coated. Irregularities in application. Same as for albumen plates (item 2, table XIII).
2. Plate does not develop uniformly. a. Plate not uniformly coated. See item 2, table XIII. Additional localized development in thicker coating areas is necessary.
b. Light or heat fog. Excessive heat in whirler during drying of plate. Also, exposure to unsafe light fogs plate making development difficult. Correct contributing causes. Prolong development to clear up fog as much as possible, assisting with sodium bicarbonate solution if necessary.
c. Overexposure. Correct on plate as for light or heat fog above. Reduce time of subsequent exposures.
d. Old solution. Correct on plate as for light and heat fog above. Prepare fresh solution.
3. Printing base does not adhere to plate. Glue not completely removed from printing areas. Remake plate, correcting contributing conditions such as light fog, overexposure, thin positives, etc. Develop thoroughly to remove glue coating down to metal. Blot quickly in drying to prevent glue from bleeding into printing areas. Rub printing base firmly into image areas of plate.
4. Stencil resists removal. Overexposure or subsequent heating. Increase strength of citric acid in reversing solution. If conditions are severe, try 5 percent caustic soda solution (wear rubber gloves) or 5 percent phosphoric acid solution to remove stencil. Then, flush with water before etching and gumming.
5. Image too sharp on plate. a. Overexposure. If noticed in development (examine with magnifier), increase developing time. Some gain can be provided on press. If fine detail is lost, remake plate decreasing exposure time or developing longer to open image areas. Also, blot quickly after washing to minimize sharpening of detail caused by bleeding of glue into image areas.
85
Table XII'. Plateomaking difficulties—glue-reversal process—Concluded
Difficulty
Cause
Correction
5. (Continued.)
b. Undercutting by printing light.
6. Image too thick.
a. Underexposure.
b. Overdevelopment.
Correct as above. For subsequent plates, temporarily blacken arc-lamp reflector to provide point source of light.
Extended use of plate etch may sharpen detail slightly. Advisable to remake plate, increasing exposure time.
If excessive so plate cannot be used, remake plate reducing development time or use less pressure on wad of cotton.
Table XI . Plate-making difficulties—gum-reversal or deep etch process.
Difficulty
Cause
Correction
1. Plate not uniformly coated.
2. Plate does not develop or develops irregularly.
3. Stencil resists removal.
4. Printing base does not adhere to plate.
5. Image too sharp.
Irregularities in application.
a. Plate not uniformly coated.
b. Light or heat fog.
c. Lactic acid insufficient or omitted.
d. Specific gravity of calcium chloride too high.
Overexposure or subsequent heating.
Gum remaining on printing areas of plate.
a. Overexposure.
b. Insufficient development.
c. Out-of-contact areas.
See item 2, table XIII.
See item 2, table XIII.
Increase localized development until plate froths over entire image area. If development is prolonged excessively, add small amount of water to developer to lower specific gravity to 38° or 37° Baume. If this does not work, remake plate correcting contributing conditions.
Mix required amount of lactic acid in calcium chloride solution as required by formula. (See par. 89c.)
Reduce to 40° Baume by adding water.
See item 4, table XIV.
Remake plate. Correct causes, such as insufficient or nonuniform development, incomplete washing and alcohol, overexposure, undercutting, bleeding, or light fog. Rub printing base thoroughly into work areas.
If noticed during development (when examined under magnifier), dilute developer slightly with water to 37° Baume. If fine detail is lost on finished plate, remake plate reducing exposure time or increasing development time.
Increase development time on subsequent plates. Check progress of development with magnifier to determine when detail is opened enough.
Results from lack of vacuum or too heavy masking or opaquing. If noticed during development, continue localized development until out-of-contact areas clear up.
86
I able XT. Plate-making difficul ties—gum-reversal or deep etch process—Concluded
Difficulty
Cause
Correction
5. (Continued.)
d. Undercutting by printing light.
If noticed during development, increase developing time. For subsequent plates under similar conditions, temporarily blacken reflector of arc lamp to provide point source of light.
6. Image too thick.
a. Underexposure.
b. Specific gravity of developer or deep-etch solution toojow.
Extended application of plate etch may reduce weight of detail somewhat. If excessive, remake plate increasing exposure time.
Raise to 40° Baume for subsequent plates by adding more calcium chloride crystals. In damp climates, increase specific gravity of developer and deep-etch solutions to 42° or 43° Baume to counteract moisture absorbed by plate coating and developer from air.
7. Image too deep.
Etching too deeply.
While plate appears satisfactory, ink roller and blanket on press do not reach image design and plate does not print or prints gray. Remake plate, reducing deep-etching time or eliminating it entirely.
Table XI I. Plate-processing
check list for albumen process.
1. Prepare solutions. Select press plate.
2. Place press plate in sink and wash with brush and water.
3. Drain plate, flow counter-etch solution, and scrub with brush for about % minute. Then wash well with water.
4. Place plate (while still wet) in whirler. Start rotating at about 35 rpm. Pour clean water over plate. Immediately after most water spins off, pour sensitizing solution on plate, spiralling coating outward from center.
5. Turn on heat, close whirler lid, increase speed to 60 rpm and spin plate until dry.
6. Place sensitized plate on bed of vacuum frame and place negative and mask in position.
7. Close vacuum frame, apply vacuum, and tilt in exposure position.
8. Expose press plate through negative for required time.
9. Return vacuum frame to horizontal position, release vacuum, open frame, and remove press plate to dry table.
10. Coat plate with thin uniform application of developing ink. Rub down smooth and fan dry.
11. Place plate in sink under running water or in tray with water, and soak for about 1 minute.
12. Develop plate with wad of cotton soaked in water, using light circular strokes (assist with sodium bicarbonate or ammonia solution if necessary) until nonprinting areas are entirely clean of ink and albumen.
13. Drain plate, apply plate etch with brush, and spread etch over plate continuously for about 1 minute. Then wash off etch with water.
14. Drain plate, place on dry table, pour small quantity of gum on plate, and rub down smooth and thin with damp rag ball. Avoid gum streaks. Then fan dry.
15. If plate will not be used for several days or longer or if required for a colored printing ink, wash off developing-ink image with turpentine. Then pour small pool of asphaltum on plate, rub down evenly with dry rag ball, and fan dry.
16. Plate is now ready for press.
87
CHAPTER 8
OFFSET PRINTING
Section I. EQUIPMENT AND MATERIALS
90. Offset Press
a. General. The rotary offset printing press operates on the lithographic principle of mutual repulsion between water and grease. It is designed to print on a rubber blanket that in turn transfers the inked impression to the paper. The press consists of a frame supporting three main cylinders, the ink and water distributing system, and the automatic feeder and delivery. (See figs. 4, 58. 59, and 60.)
b. Cylinders. The main cylinders of the press are the plate, blanket, and impression cylinders. They are geared together and operate in rolling contact.
(1) Plate cylinder. The upper, or plate cylinder is undercut and provided with adjustable clamps for receiving and positioning the press plate strapped
around its circumference. \\ ater and ink are fed to the press plate from separate fountains. The ink fountain feeds a thin controlled film of ink through the distributing and form rollers to the greasy areas of the press plate. 1 he water fountain has a more simple distributing system.
(2) Blanket cylinder. The intermediate, or blanket, cylinder is undercut to receive the rubber blanket. It is equipped with clamp bars and a reel for stretching and holding the blanket taut around its circumference.
(3) Impression cylinder. The impression cylinder generally is not undercut and is not provided with a plate or blanket covering. It is mounted to permit adjustment for printing on different thicknesses of stock. Cam-operated paper grippers contained in the cylinder recess pick up the sheet of
INK FOUNTAIN
V WATER FOUNTAIN
• ■>. LtV 'I // \
UTF , •, 1 PRESS EEED
press efr'
DELIVERY I
I i r ■
\ I
Figure 58. Multilith 2066 press.
88
paper immediately after registration and carry it through the press. After the paper receives the inked image from the rubber blanket, the grippers release it to the press delivery, which deposits and stacks printed sheets in a pile.
(4) Cylinder relationship. Bearers at each end of the plate and blanket cylinders roll in contact with each other during the printing operation. They have the same diameters as the pitch (rolling diameters.) of the driving gears. The cylinders are undercut between the bearers by several thousandths of an inch more than the thickness of the standard press plate and blanket. This permits underpacking the press plate and blanket with several sheets of paper to bring their surfaces into true rolling contact with the recommended .003-inch printing pressure. It also permits changing the effective diameters of plate and blanket cylinders by adjusting the underpacking (make-ready). In this way, compensation can be made for variations in size
of the paper stock caused by differences in the relative humidity. By removing the underpacking from beneath the press plate and placing it under the blanket, the image size can be increased without altering the printing pressure. Maintenance of .003-inch printing pressure is essential to good reproduction. Less pressure may result in gray or unprinted areas. Increased pressure (often mistakenly attempted for obtaining better printing quality), or excessive under-and-overpacking, causes serious friction between the press plate and blanket shortening the effective life of the press plate.
c. Feeder. The feeder separates the sheets of paper to he printed, and delivers them one at a time to the press guides. An elevating platform raises the paper pile gradually as the sheets pass through the press. An attached blower separates the upper sheets, and a vacuum suction device lifts the top sheet off the pile, depositing it on the tapes of the feeder hoard. As the sheet passes down the
\
~WATER FOUNTAIN , / PRESS FEED
INK fountain-^ v 1 Wk ” / /
■life,.. ~~ M- JF'X-, /.
ftnJ/
i.-Lfldg /■ IT*
I ...J) 1 Mg g
PRESS D F i1 VERY YF
jdRBkJT r
aS? .... 1
Figure 59. Harris LTE press.
89
feeder board runway toward the cylinders, it is positioned by the front and side guides before it is picked up by gripper fingers of the impression cylinder.
d. Press Delivery. '1 he press delivery usually is a chain carrier equipped with crossbars having gripper fingers that seize the sheet just as it is released by the grippers on the impression cylinder. I he chain delivery carries and stacks the sheets evenly on an elevating platform. The platform is gradually lowered as the printing progresses.
e. Mechanical and Chemical Control. The offset press requires both mechanical adjustment and chemical control for satisfactory printing. Supply and distribution of ink and water to plate are essentially mechanical, but the reactions between the ink and water are chemical.
(1) li ater and ink distribution. Correct reproduction requires a proper balance of water and ink on the press. Too much water or fountain etch may sharpen or undermine the work, resulting in loss of detail as well as printing density. Too much ink or insufficient water induces scum, thickening of the characters, and plugging of the shadow tints in the halftones. Similarly, improper make-ready results in gear streaks and slurred detail or dots, gradually wearing down the albumen image and the grain of the plate.
(2) Acidify of fountain solution. Inks issued are standard inks and require little adjustment. (See par. Qib.) However, the fountain solution is more critical and must maintain a definite degree of acidity to minimize swelling of the albumen image, plate scum, and emulsification of the ink. While the
INK FOU NT Al N
J WATER FOUNTAIN PRESS FEED
PRESS DELIVERY J
■ Er
V.. I E
x,' •-
k ' \ ' 3W>-; J ?S
% W..F ♦ ~
TR(HiE8|r * ■ * ...---------------------------------------------------—---------- — ......
Figure 60. ATF Webcndorfer 29 press.
90
correct percentage of each ingredient can be determined by trial and error, more consistent results are obtained by controlling the fountain solution during operation. This is done by using the pH indicator that measures the acidity of the fountain solution. (See par. 91c).
(3) Registration control. Although humidity variations cause paper to shrink or stretch, proper press adjustments enable obtaining correct size in the initial printing, and assist in maintaining register when adding successive colors. Registration is more readily controlled by preconditioning the paper stock and by keeping the moisture content of the paper and the humidity of the pressroom constant during the entire run. A 50 percent relative humidity is best for the pressroom. However, any constant humidity that can be maintained throughout the press run is better than a varying humidity.
(4) Mechanical adjustments. Offset presses are adjusted and tested at the time of their installation. Minor adjustments are usually necessary every time the press is started, and others are required to compensate for wear. All major corrections, such as timing or aligning cylinders, must be made only by qualified personnel.
91. Printing Materials
a. General. Materials used in offset printing include inks, driers, varnishes, fountain solutions, and paper.
b. Inks. (i) Characteristics. Lithographic inks must be greasy, have fairly high color density, and be of proper consistency and tack to transfer from press plate, to blanket, and finally to the sheet of paper. Since lithographic inks are constantly in contact with moisture and acids on the press, they must not be chemically altered, emulsified, or subject to bleeding of color. The ink must set properly on the sheet so it will accept (trap) subsequent color printings. The ink must dry in a reasonably short time. The dried ink must also be resistant to chalking, smearing, bleeding, and fading.
(2) Composition. Lithographic inks are a mixture of a pigment or dye, a vehicle (varnish), a gi easing agent, and sometimes an ink extender. These are ground together in a mill until each pigment particle is thoroughly coated by the vehicle. Since the tendency of inks to “liver” (congeal into a rubbery mass) is accelerated by driers, the driers are usually supplied separately and mixed with the ink immediately before use.
(3) Classification. Inks are classified as trans
parent, semi-transparent, or opaque, depending on the nature of the pigment or dye and the ink extender used. The opaque inks usually are used for first printing colors or where good ink opacity is required on colored stock. The transparent inks are used in process color work, where subsequent printings must not block out the previous colors. The opaque inks generally have a higher specific gravity and greater permanence but print less sheets per pound of ink than the transparent varieties.
c. Vehicles. The vehicles or varnishes generally used in lithographic inks are boiled linseed oil, tung oil, soybean oil, perilla oil, or synthetics. All these vehicles dry at varying rates by polymerization, oxidizing and changing from a soluble liquid to an insoluble congealed form. This drying is further accelerated by incorporation of driers. Boiled linseed-oil varnishes are assigned numbers corresponding to their viscosities, ranging from No. 0000 (lightest) to No. 8 (heaviest), sometimes called body gum, that has high viscosity and rapid drying properties. Lithographic inks are usually ground in a No. 3 varnish. If the ink must be thickened or thinned, small proportions of a lighter ( No. exo) or heavier (No. 8) varnish are added until the required consistency is obtained.
d. Driers. Driers are catalysts that accelerate the drying of the inks. Although many chemicals can serve as driers, the two issued are cobalt (cobalt linoleate) and paste driers. The cobalt driers are the fastest and tend to dry from the surface down. Paste driers are slower in action, but drv uniformly throughout the ink. Cobalt driers are used, extensively in single-color work, where rapid drying and a hard glossy ink surface are desired. Paste driers are more frequently employed in multicolor printing, where the previous, colors must set with proper surface and tack to accept those that follow. The amount of drier used depends on its concentration, the color and pigment of the ink used, the printing conditions, paper stock, and the prevailing humidity. The addition of more drier increases the drying rate to a certain extent. Excessive amounts cause the ink to dry in the fountain or on the rollers, and may result in emulsification, chalking, and piling of the ink. Inks supplied to field units are prepared for average conditions. Aside from adding the recommended type and amount of drier, the ink should not be mixed with other ingredients. (See par. 103&.)
e. Fountain Solutions, (i) General. The offset press can be operated with water alone in the fountain, but control is difficult and there is a tendency for the plate to scum or the ink to emulsify.
91
INCREASING ACIDITY
NEUTRAL
INCREASING ALKALINITY
FOUNTAIN SOLUTION RANGE-*] 01 2 3 4 5 । 1 1— i h— 1 6 ->| ALBUMEN SENSITIZER RANGE ? 9 IQ 11 12 13 14
10,000,000 | 100,000 | 1,000 1 10 1,000,000 10,000 100 ( RELATIVE HYDROGEN ION (H + ) CONCENTRATION PURE 10 1 IzOOO 1 100,000 I 10,000,000 ) 100 10,000 1,000,000 RELATIVE HYDROXYL ION (OH-) CONCENTRATION WATER
Figure 61. pH scale.
Addition of a fountain solution to the water stabilizes the ink and press plate against break-down, or deterioration. Besides replenishing the protective ink-repellent film on the plate, the fountain solution also reduces the tendency of the albumen image to swell, preventing the loss of its affinity for ink. The acidity of the fountain solution retards emulsification of the ink, but dissolves the grain of the metal plate, undermining the printing image. For best results, the acidity of the fountain solution must be maintained at a pH between 3.8 and 4.6. (See fig. 61.)
(-) pH of solutions, (a) The pH value is a measure of the degree of acidity or alkalinity of a solution. It is expressed in numbers ranging from o to 14 in which a pH of 7 represents a neutral solution. As pH increases above 7 the alkalinity increases; as pH decreases below 7 the acidity inti eases. 1. See fig. 61.) Since the pH scale is loga-1 ithmic, a change of 1 unit of pH changes the acidity or alkalinity 10 times. For example, a pH of 4 is 10 times as acid as a pH of 5.
(Z?) Free acid in a fountain solution neutralizes itself rapidly by reaction with the metal in the fountain or the press plate, but this reaction can be delayed considerably by including buffers in the solution. The buffers are usually salts, such as magnesium nitrate, that stabilize and prevent rapid change in the pH of the solution.
(c) 1 he pH of a solution can be determined by colorometric or electrometric methods. The coloro-metric methods are not as accurate, but are simpler and better adapted to field use. They determine pH by the change of color resulting when selected dyes are placed in solutions of different acidities or alka-linities. 1 he pH is indicated by comparing the resulting color with a reference standard.
f. Map Paper. Map paper must be strong, relatively stable, and have a suitable surface to accept and hold the printed ink detail. The high wetstrength paper supplied meets these requirements.
(1) Shrinkage and grain. (a) All papers absorb moisture and are subject to shrinkage and stretch with varying humidities. Paper, like wood, shrinks or stretches more across the grain than along the grain (machine direction). Since the variations in paper size between printings on a multicolor job are largely across the grain, some compensation for color register can be obtained by changes in underpacking beneath the press plate and blanket. I his enables the press to print longer or shorter in the direction around the cylinder, but cannot compensate for changes across its width. A varying humidity may cause paper stock to curl or develop wavy edges, and improvised attempts to correct this condition with heaters or fans are seldom effective. Paper can be conditioned for use by hanging or spreading it in the pressroom until it is stabilized with the humidity of its ■ surroundings.
(Z>) Paper stock is preferably stored where the relative humidity is 3 to 5 percent higher than in the pressroom because paper is more easily controlled when losing than when gaining moisture. Since humidity control is difficult in mobile units, the press operator must learn how to handle paper under adverse conditions. These problems are particularly difficult when emergency paper stocks other than the high wet-strength paper must be used.
(2) Paper surface. A smooth paper surface permits transmitting finer detail and better halftone dot formation than an unfinished paper. (See fig. 62.) The smooth surfaces of coated papers repro-
COATED STOCK UNCOATED STOCK
Figure 62. Paper surface and dot structure.
92
duce better printing detail, but their susceptibility to abrasion, folding, and moisture makes them less satisfactory for map work. The tendency of coated and unfinished papers to pluck (lift away), may necessitate reducing the tack or length (stretch) of the ink by means of light varnishes or “dopes” with a resulting loss of color density. Machine-finished papers may be smoother on one side than on the other because in manufacture the pulp is deposited as a thin layer on a fine-wire mesh belting so the fine fibers on the bottom are carried away with the
water solution before the paper is passed between the finishing rollers. The smooth or “felt” side of the paper is the top side contacted by the felt belt while the paper lies on the wire mesh screen in its passage through the rollers. Coated paper has a deposit of white clay, oxides, or other materials suspended in casein vinyl alcohols, resins, or other binders impregnated into its surface. Since some paper coatings (those containing alum) induce scum on the plate, only coated paper made for offset should be used.
I-----------1
I DROP-DOOR |
I LOADING |
I PLATFORM |
I___________ I________________________________________________
rr* । ~ 1 1 । O
?'---- INK TABLE’; /mT
c’ ENTRY /
______________________| DOOR /
ROLLER > /
RACKS m /
/ 22" x 29" 5 BLACKOUT TRUCK-BODY
/ OFFSET LITHO PRESS Q CURTAINS EXTENSION
in \
\
LU \
QC \
| c > FOLDING
TABLE PLATE RACK CONTROL PANEL FIELD TABLE
I---Z--------, I I I I; 1[
। -.। ..I %l- -■I
TOOL PANEL
Figure 63. Press section.
Section II. PRESS OPERATION (PREPARATORY)
92. General
The sequence of operations in this section is general for all presses and is intended to guide in standardizing adjustments and control. They must be coordinated with instructions in the training manual applicable to the press supplied to the topographic organization.
a. Press Performance, (i) Successful printing on the offset press depends on a satisfactory plate and on the proper adjustment and control of the press. Reproduction characteristics that depend on press performance include full color density in the
entire printed subject, correct dimensions, fidelity of printing design without gain or loss of detail, and color register.
(2) Full color density means that the black ink prints black, not gray, the red prints red and not pink, etc., with the other colors. Also, colors must not change during the press run.
b. Maintenance References. Information concerning care, adjustment, servicing, and operation of offset presses used in map reproduction units are covered in TM 5-6020 and 5-6022.
93
SUCTION HOSES
^^^^■■Tpressure^' ■
ADJUSTMENT
K\ FOR FEED
_^a^ggSSSSS BhUSr ^Wr ShK^----------------------------S— TWO-SHEET CHOKE
FEEDER
JjZpJL F+\ SUCKERS
pH^TEIGHTMftj^a^^OBP^ ■ A
, j^^B^EBISIBBiiKKi
H B^fl|E^^DB^F. ’Na^ ,,
I b ''-■ ~ ’L i
--w, ^-***i><*S^ ^hk.
<•'« RECIPROCATING^^-' ^38" ST ' ”’
|J ■-IOE_ GUIDE ; > 1
\ V ’’^BB '' :s *MwBflS^ J
p<|tx x. ^wIS^ x «vF BBB
Bwflfln^k x99HBBHKik. 2X. paper B
MICROMETER MRGBlk xBB? ^^'''‘'jjfc. HOLDDOWN B
M ADJUSTMENT IflfljBBBk STRIPS
■ for stationary
■ SIDE GUIDE ^flKif '□flh. V^
^■wuvjssy'^ x La^tKKK^ &«. al
Figure 65. Paper guides, Multilith 2066 press.
-. x- iX-^-t
PRESSuRE SSSBk ./JiikX'X’ uF^^Wfli
THROW-ON 1^' W^' ‘ ""J/V Cf ■ PAPER-FEED-ROLL^
LEVER •> v. ■ a- 8 / pressure .
\ "'? r %• EbMP1^
BIBJE^BeX, <^7 '""-ju7-"™
■'-^ f-aV JJ- k. ■ y ■. y ^u................,
/. jr^- y. - ’B' < . flip i9B»^2f KBk^
VN*cf .<" ■ wCilBK
jjfapM : •■ iB^.IzX/J/x ' ;.'lt•)•■■ •
Mfl handwheel ■ Rj^KjR&ni
X’rCi^n'Hn I I ADJUSTMENT CYLINDER- ^M'i
ADJUSTMENT Ofllfl'
Figure 66. Controls, Multilith 2066 press.
95
93. Conditioning Paper
Where space is available, hang or stack the paper, flexing (winding) it at frequent intervals to get air between the sheets so it can acquire a humidity equal to or preferably slightly in excess of that in the pressroom. (See par. 91c.) When paper difficulties are experienced and humidity control is not possible, the paper can sometimes be conditioned by running it through the press with a blank plate and dampeners on.
94. Lubrication
All moving parts of the press must be lubricated regularly for continued satisfactory operation. Lubrication must be done while press is not operating. Lubrication instructions are in training manuals. If manuals are not available, proceed as follows:
a. Oil Daily, (i) All oil holes marked “oil” or indicated with a red spot.
(2) Tumbler shaft and gripper shaft at each end of impression cyclinder. (Use lohg-spout oilcan and wipe off excessive oil.)
(3) All ink and dampener roller bearings.
(4) All cam rollers.
b. Oil Weekly. Delivery chains. (Use SAE 20 oil cut half and half with kerosene.)
c. Grease Weekly. { 1) All gears. Use gear compound, after first cleaning out any accumulated dirt between gear teeth with a small bristle brush.
(2) All fittings on feeder, fountain, and press bearings.
d. Oil or Grease. Electric motor.- at intervals recommended on instruction sheets.
95. Mounting Blanket
The metal clamping bars must be accurately attached so the rubber blanket is stretched uniformly over the cylinder.
a. To attach the bars, place the blanket on a flat table with the bars over the leading and trailing ends. Carefully align the bars so they are parallel and in alignment. Then scribe on the blanket the location of each of the screw holes, and carefully punch the holes. Fasten the bars to the blanket, checking for
yjEjk DAMPENER DUCTOR ROLLER
FEED LEVER ✓
-^O^OLLER^ \Z
.-. v*"*"'”"’ -j V
DAMPENER jgfcr'-'''''''' Vii
|lORM-ROLlER cXhLVauGpoiifR ’ FOUNTAIN-SOLUTION F E E 7Y WJM |
I IHR^.° I I MANUAL FEED - -■ AND CUT?FF tEVFL..L^Wr3W|WWI I
I kXl RECEPTACLE'fOR^I
gpEF \r 1L iMBF' ~ • fountain solution I
uRk TH bottle
t JR I AEsflR
mPjlaAT Wfttk ---■}K-a - | IgM
tr k ^09
HMk WATER STOPS
Mk (WIPERS)
Hk* iH x ^A-xWMr'"v ^EfeAX> ' x Ttew
Figure 67. Water fountain, Multilith 2066 press.
96
DUCTOR DISTRIBUTING
ROLLER. ROLLER.
INK-FOUNTAIN \ /
ROLLER x. I /
INK-FOUNTAIN M /feed handle, al
IN K F O U N T AIN / jflBS
BLADE<>MT>h« V' '%
FORM ; ROLLER-----
INK-FOUNTAIN Xf^fcSsZl
ADJUSTING SC FEvVS<*>^ V.W ■tM *■• ’ L-/v^
form-roller
jtfStfnHn^'^ handle — .'./%r
Figure 68. Ink fountain, Multilith 2066 press.
parallelism before tightening the screws. It is advisable to prepare an accurate metal template with holes drilled in the exact location for marking the blanket. Because of the time delay in mounting a new blanket, a second blanket with duplicate clamping bars attached should be kept available.
b. \\ ipe the face and back of the blanket with a dry rag and clean the surface of the blanket cylinder. In applying a new blanket, thoroughly wash its surlace with a-rag and clean water, and scrub with pumice powder. Then dry the blanket and dust its surface with a powder consisting of a half-and-half mixture of flowers of sulfur and French chalk contained in a small muslin bag. W ipe clean with a dry rag.
c. Attach the front bar of the blanket to the blanket cyclinder.
d. Measure the average blanket thickness at several points with a micrometer. (Do not compress the rubber.) Select several sheets of paper of the same width and long enough to underlay the blanket completely. Insert several under the front end of the blanket so their combined thickness added to that of the blanket brings the surface of the blanket up to bearer height. (The figure for this thickness is usually stamped on the blanket cylinder or can be obtained from the Technical Manual.)
e. Turn press over by hand to draw the blanket and paper underpacking around the cylinder. Take care the paper does not wrinkle. Insert the backend of the blanket with its attached bar into the reel holder, and bolt the bar in position.
f. Stretch the blanket taut over the cylinder, using
97
the wrench provided. To prevent the cylinder from moving, hold the handwheel or insert the cylinder stop pin located on the operator’s side of blanket cylinder.
96. Mounting Press Plate
Check the press plate for damage, defects, and errors in position by comparing it with proof copy or other reference sheets. If satisfactory, mount plate as follows:
a. Extend gripper reference marks on press plate to sides of plate and to center of gripper edge if they are not already printed or drawn.
b. Wipe off back of press plate and face of plate cylinder with sponge and water. Then clean with gasoline on rag and dry with clean rag.
c. Loosen all plate clamps and clamp screws on plate cylinder.
d. Raise ink-form rollers up to off-contact position.
e. Put press on impression by pushing impression throw-on lever down after first placing a strip of paper under the sheet detector. On the Harris press, grasp pins on impression arm and throw on impression manually. Then turn press over one revolution with the handwheel.
/. Insert front edge of press plate centrally into plate gripper bar, aligning reference marks on plate edges with corresponding center and side marks previously engraved on gripper bar and press cylinder. Tighten plate clamping bolts from center outward. Raise clamp bar and bolt in position.
g. Measure average thickness of press plate with micrometer.
h. Select one or more sheets of paper for underpacking plate so total thickness of plate and underlay will be .003 inches above bearer height (to provide .003-inch printing pressure against blanket). Then, carefully insert paper underneath gripper edge of press plate and turn press slowly over by hand, making certain paper does not wrinkle under plate as it is drawn around the cylinder.
i. Insert back end of plate in rear clamps (bend plate slightly if necessary), and tighten clamps.
j. Remove paper strip from sheet detector. Trip press and revolve one turn “off” impression.
k. Again check clamps for tightness and make certain plate is drawn taut around cylinder. Test by tapping portion of plate bridging clamps and cylinder, listening for a sharp ring.
I. Finally, lock clamp-bar bolts in clamp slots. Then, run press for few seconds, stop press and
Hr'ji
'REAR JOGGERsMt^;^
Z ^-"SIDE JOGGERS^ '
■ thi ■ ■ FRONT
- ■ Em stop “Bi
**^5^***^ K K CLUTCH/■
■ K THROW-OFF HBfloH
lever
DELIVERY P
Figure '6g. ' Press delivery, Multilith 2066 press.
98
PULL-IN WHEELS
PILE-HEIGHT
ADJUSTMENT SCREW
PRESSURE-
BLAST FOOT
OSCILLATING SUCTION HEAD
PILE ELEVATING HANDLE
[VACUUM | CONTROL
VALVE \
ADJUSTABLE CORNER BRACKET
BACKLASH BRUSH
HOLD-DOWN-. WHEELS /' ■ FEED-BOARb^ TAPES /
AIR-BLAST NOZZLE
SHEET- g
SEPARATION I FINGER
Figure 70. Paper feed, Harris LTE press.
99
check to see that blanket and plate are still taut. Care must be taken not to catch tools or clothing in the moving machinery.
97. Fountain Adustments (figs. 67, 73, and 79)
a. Prepare fountain solution by using 1 ounce of etch (par. 105) to each gallon of water and adding phosphoric acid until pH is between 3.8 to 4.5. (Where pH testing equipment is not available, phosphoric acid content can be doubled or the alternate formula listed in paragraph 105^ can be used.) Most fountain solutions contain chromates which may cause dermatitis. Avoid hand contact. Wash after exposure. Pour prepared solution into water fountain so bottom portion of brass or muslin-covered fountain roller is immersed to a depth of % to % inch.
b. Wet all dampening rollers evenly with sponge. Dampening rollers must be damp enough so they do not accept ink from plate, but not so wet that water collects on plate surface.
c. Adjust all dampener rollers to plate and to each other using strips of cellophane along several positions and testing for even firm pull. Check dampener ductor in positions of contact with fountain roller and with intermediate roller.
98. Feeder Adjustment (figs- 64. 70, and 76)
a. Jog and flex the paper on a table or box to wind or air it properly and then load on the feeder board, stacking sheets carefully against side and front guides. (The side guide is adjustable for centering pile.) Add about 50 waste sheets, interleaved with 10 clean sheets, to the top of the pile for use in adjusting the ink and guides when starting press.
b. Raise feed board by turning hand crank until top of paper pile is about % inch below pile-height governor. Then set corner guides against paper pile, and position paper-separation blowers along back or sides about % inch away from paper pile. Adjust suckers so they are between the feed rollers. Then, turn press over by hand until suckers are at their lowest position, and raise paper pile until top sheet is % inch below suckers.
c. Adjust two-sheet choke with thumbscrew so one sheet of paper passes through freely but the thickness of two sheets catches and prevents passage of paper.
d. Set sheet stripper finger by turning adjusting screw until spring fingers press lightly against top of pile. (Screw may require further adjustment after feeder is in operation by setting pressure to
. .
■ H’Ont sheet.choke
fnit adjus’men^J||
— - - - flattening
X ■ X: Z BAR
g SIDE-GlflDE .
aAmusTMENT^gC,„5IDE
KTholddown
PAPER x
sheet X, VW.
Figure 71. Paper guides, Harris LTE press.
100
M- '
ON
OFF
HANDWHEEL
CLUTCH LEVER
THROW-OFF g ADJUSTMENT j
MANUAL TRIP LEVER
STUDS
FOR MANUAL PRESSURE THROW-ON
IMPRESSIONCYLINDER-ALIGNMENT ADJUSTING NUTS
» PAPER- W
THICKNESS ' W ADJUSTING B gF HANDLE AND W |h INDICATOR B (Release cap screws each side of press before adjusting)
FEEDER (LEVER HALF-DOWN) _....—
FEEDER & PRESSURE (LEVER DOWN)
Figure 72. Controls, Harris LTE press.
101
DAMPENER FORM
WATER PAN
DAMPENER-FORM-ROLLERS ___HANDLE
MUSLIN-COVERED PAN ROLLER
ADJUSTABLE WATER CONTROL CAM
WATER DUCTOR ROLLER
ROLLER .
DUCTOR-ROLLER ADJUSTING SCREW
DAMPENER-DUCTOR FEED CLUTCH
A ■
Figure 73. Water fountain, Harris LTE press.
102
x hand feed INK-FOUNTAIN
Xx / ROLLER ' DUCTOR
rOLLER DISTRIBUTOR INK-FEED
X;. ROLLER CONTROL
_/ Rider Zz
\a<: x^^x^sSBii^^wiCt-} ■
INK-FOUNTAlN f - - i 1
BLADE ~ * ,^^HbtC^H *1®^/
WASHUP -ATTACHMENT 1 • I W Wr/^wBRB^
PRESSURE SCREW • -Ik
K|Hb x^s^w?mi4h /"
%(-*'<■ WS '> IRIBUTION VEoHBjwX
TR PP'NT'NGrWBi^.^ll '•’ |.
j^^iHh^. K-- w iRif —J-'- itw». T^Mi^PaB
-----------------------wBb^S* LW23®W *k 'Pi
ink-ductor-------------\ «W .x^WreSCI
lever ^+F®bi R°L!-tR HJkj >^bS 'V*^
distribution xSr* B
wb^only jSf’l x iS.
j^LaskasMBMMCBMMfefc.
v FORM-ROlLER >"
'■ handle
Figure 74. Ink fountain, Harris LTE press.
103
RAISE
STRIPPER FINGERS
END-GATE FINGERS
liS ADJUSTABLE ■ SIDE-JOGGER-PLATE MMrodJBHBF
AUTOMATIC DELIVERY-PILE
BAR RECEDING ADJUSTMENT,
REAR JOGGER PLAT?—? ,
DELIVERY CHAIN
CHAIN-TENSION ADJUSTMENT
END-GATE
LIFTING LEVER
SIDE JOGGER Pl ATE
PAPER GRIPPERS >. .. Kfe/L,;.:,.
DELIVERY BAR
DELIVERY-PILE HOIST HANDLE
Figure 75. Press delivery, Harris LTE press.
104
fl SUCKERS
i 1 l. z ^jKR a^fcx^
JpF — <\Zm~
^>^sid^TKMBBEmL^”^f<.^-.. J( £Diil_
■KFE I . IW ..jg^f/j^Wy... Z i! n n ,
OIL PUMP
CYLINDER TRIPLATCH HANDLE
AUTOMATIC SLOW-DOWN
DELIVERYPILE HANDLE
ADJUSTMENT FOR DELIVERY- fc PILE LET-DOWN 1
IMPRESSION-CYLINDER ADJUSTMENT HANDLE
IMPRESSION THROW-ON LEVER
AIR SUCTION LEVER
IMPRESSIONCYLINDER ADJUSTMENT LOCK
Figure 78. Controls, ATF IFebendorfer press.
107
FOUNTAIN
DUCTOR ROLLER
ROLLER
WATER STOPS
FOUNTAIN PAN
DRIP PAN
WATER-MOTION THROW-OFF LEVER
WATER-MOTION THROW-OFF LATCH
DAMPENER
THROW-ON HANDLE
WATER-MOTION CONTROL
DAMPENER VIBRATOR-ROLLER SHAFT
DAMPENER FORM ROLLER
Figure 79. Water fountain, ATF Webendorfer press.
108
FOUNTAIN
DUCTOR ROLLER?
VIBRATING
RIDER ROLLER
VIBRATING ROLLER
FORM ROLLER
INK-DISTRIBUTION ROLLER LEVER
FOUNTAIN BLADE CLAMP SCREWS
INK ADJUSTING THUMB SCREWS
HAND-FEED
RATCHET LEVER
FORM-ROLLER ADJUSTMENT TO PLATE
INK-MOTION THROW-OFF LATCH /
INK FORMROLLER THROW-OFF LEVER
INK-FOUNTAIN / BLADE
AUTOMATIC FEED ADJUSTMENT
Figure 80. Ink fountain, ATF IFebendorfer press.
109
area, an opening of about one-half turn, or .01^-inch gap as tested with feeler gauge can lie used in the preliminary setting. Set ink-fountain ratchet pawl in halfway feed position. (See figs. 68, 71, and 80.)
c. Put the ink in ink fountain and spread it along the fountain roller in a uniform layer until fountain is half full.
d. Rotate press to bring ductor rollers into contact with fountain roller. 1 hen, turn fountain-roller hand ratchet and examine ink distribution by thickness of ink layer on roller. Open or close thumbscrews if necessary so ink layer corresponds to
approximate ink requirements along the plate.
e. Check ink rollers for proper contact with each other and with plate, using thin slips of cellophane or a .003-inch feeler gauge. Run press for several minutes to distribute ink on rollers. Stop press and test for uniform contact of form rollers by dropping them against gummed-up plate. Then, raise rollers and note ink marks for uniform :i/16- or inch bands across plate. If bands are not uniform, form rollers must be adjusted according to instructions in press manual. 1 he end of each removable ink-roller shaft should be numbered or marked so it can be replaced in the same location on the press.
- ■ awT-CXx y >"> xZCzXx/,?/,-/;
Z ' 'X 4
Z5".. ' -• -X-
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AUTOMATIC ‘ V" ' -• X " vZ I
BEIT-ALIGNMENT AQ ,.._.M G I
REGULATOR V . 1
X. t ‘s Xx>’ "*■—0 drums
dryer p** ■-—®C, - •' 3
belt .. IkWWk ■ J B
\\ ■ WS S~-'
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met -x---------------- jF^K? ■. 2/ + \W 1
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aln li k v\ - 1
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BH ® i jw X±rrM 1 1 I motor
|nL. «' X-«*4 oA - . / «****^**x: ? I /
1 WASH TANKS ‘ > ' j gF\~' || j
ii IHNbrs: \'s''s *14 ~
te*• \ W1k|k
HJf -"• ;■■ nX ‘v. ai w1*"!
fe fi' .4 I T ’Sil
figure gj. Wash tank and drier units, rapid projection printer.
130
COPYBOARD AND
LENSBOARD. X CAMERA LAMPS ______
CAMERA BACK. ’ \----------
r’r?;:--7 7 SB X? t ICTWMBT' Filial
MM q ® g |
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VACUUM PUMP AND TRANSFORMER
Figure gg. Task force camera.
WHIRLER
A, TRAY FOR
TABLE LEAF Xtx DEVELOPMENT TABLE LEAF
....-■ _ ■■■i. -11 fim.JiiWMMW'W'-—".''
(OPEN)
Figure 95. Task force plate-processing unit.
8 31
FOUNTAIN ’ _ «K FOUNTAIN
(I • »■ - imiia**-
la [Mb'S!? jf/
■M& & z friction
fi I Bwlb- k mra F EED
J |fe ' i !► ’ 1 w*'’ ~ i B — iB
SPEED I IK. 7 " WJ .
CONTROL -fiMIMI^k^WS '
^aL 11 mR*
DELivERY '^>>l111^^
1
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‘7'T . '-- 1 m
•• • * ■ -Ju yf SB \s
: ■ --'.j -TV
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Figure 96. Task force press.
132
SHEET DETECTOR THROW-OFF
MICROSWITCH THROW-OFF FOR TWO-SHEET CHOKE
SIDE-GUIDE
PAPER PULL-OUT WHEEL
H SQUARING /
■jXX ' JMIMI ADJUSTMENTS / /
/ \ TWO-SHEET / /
™Hrr . .xml'/rfMnfir fi-- - -. \ choke / /
/ --_____"-
U i/E3 9/
iH.^Tfl1l**i|i|i>L / jjw/v^^- ___—j
dt/S^k ^r-
I SIDE-GUIDE ' •' PAPER-FEED Z J FEEDER CLUTCH CONTROL / f
HO MICROMETER PRESSURE ‘’X'HHHHHHH^'^A ‘ 4
ADJUSTMENT CONTROL fX I*.
* -'Z . fix' J*
FEED BOARD
Figure 97. Friction-feed task force press.
133
-ax*"’/
FOUNTAIN RESERVOIR
WATER -FOUNTAIN
WATER-FOUNTAIN ROLLER
FOUNTAIN DUCTOR ROLLER
DAMPENER DISTRIBUTING ROLLER
DAMPENER FORM ROLLER
FOUNTAIN-ROLLER MANUAL FEED
DAMPENER-FORM-ROLLER
THROW OFF
LEVER
FOUNTAIN-ROLLER FEED S AND THROW-OFF CONTROL
iff A
- si
STUDS FOR HAND-CRANK OPERATION
Figure 98. Fountain controls, task force press.
134
/ DUCTOR control
^SfcJ^C OFF LtIonS
-3* FOUNTAIN
roller
■■■" FOUNTAIN'FEED £^i^.)r7VA
/ <^r AND THROW-OFF cniiMTAiM
"-T JL. L ( W rrNKiTDMi .11 FOUNTAIN
^-M'- 7^ ~°L --- BLADE
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WrlfiX- W11b. ' ><□
Jgk. C<-»Fy 0 ■ ■ ■<6Nk.’ vB *£
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» 4 DECREASE ADJUSTING SCREWS
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■K ....FORM ROLLER O£ ' ”’^>g
M THROW-ON LEVER * W;
MANUAL
fe^|||3r ^wRil ink-fountain-roller
V'.,.. ..FEED
3M HF^y
..ak. '7 . D"-- ■■-' "77 1 uhHfj3^«Mwr
vstiWU - I Wr
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Cabinet layout layout I DOOR /
TYPEWRITER , TABLE TABLE I II STEPS
TABLE ___________j||l JI 11—l|| < |[ ||i
BLACKOUT i' TRUCK-BODY
CURTAINS I) EXTENSION
LABORATORY II f j I F^imnG
TABLF SINK WORK TABLE 1 FIELD
IABLt blNK REFRIGERATOR > TABLE
IL—J I
V- I........i "1---------------- If] hrr. —.-....
Figure 100. Hq and laboratory section.
137
d. Prepare and lubricate equipment for operation, clean utensils, and mix solutions. Make tests where necessary to determine exposure or development time.
I 16. Water Supply
( 'peration of the individual map reproduction units is modified by the nature and availability of water. I his is particularly true in preparing solutions and in the thoroughness with which washing of plates and negatives can be carried out.
a. Impurities. The water supply should not only be free from visible impurities but also must not have chemical effect on prepared solutions. \\ ater that contains considerable organic matter or dissolved minerals may cause fogging, scumming, or precipitation of some of the chemicals out of the photographic solutions. Also, it may affect the albumen sensitizer used in plate processing. If water contains a large amount of such impurities, use distilled, rain, or boiled water for preparing solutions, using normal water supply only for washing operations.
b. Filtering, if water purification trucks and adequate filtering facilities are unavailable, and the local water source appears turbid, use the canvas tank to settle the impurities. Then, filter through available filters or improvised pads of cheesecloth with a square of absorbent cotton between, so the water is comparatively clear.
c. \\ ater Lines. Where a water-purification system is provided, chlorinating and filtering minimize difficulties caused by suspended matter and growth of algae in pipes and tanks. Pumps, tanks, and circulating system must be drained where freezing conditions within the mobile units are anticipated.
I 17. Electrical Equipment
The mobile map-reproduction equipment is designed to operate on no-volt, 60-cycle, single-phase, alternating current. The power is obtained either from 5-kw portable generators or from the local power-supply source. This current is normally available in most of the United States. However. local variations in cycles, voltages, and nature of the current make the use of local power supply inadvisable unless the electrical source and the capacity of the power lines are confirmed as suitable feu operating the equipment. Since most foreign power supply is rated at 50 cycles and 220 volts, either step-down transformers or the portable generators are generally used.
u. Standard Generator, The standard 5-kw portable generator (TM 5-5044) is rated at 7.2 kva with a permissible overload of 75 percent for a period of 2 hours. However, it may be inadequate when operation of all equipment is simultaneously attempted, or when several units are supplied with power from the same generator. Because of this, operation of equipment may have to be scheduled for intermittent service. The a-c generators cannot operate in parallel to increase the power supply since they cannot be synchronized manually. Joining generators in parallel may cause huge current surges and burn out the equipment. Since the starting current of most motors and arc lamps is several times larger than the operating current, switching on one unit affects operation of others supplied from the same generator. This is particularly important in the camera section because current changes affect the quality and intensity of the light. Therefore, it is desirable to operate the camera section from its own generator and to switch off the temperature-control unit during the exposure period.
b. Operation On 50-CYCLE Current. Operation of the mobile map-reproduction sections in areas having 50-cycle power that has been stepped down to no volts is generally more suitable than the portable generators. It permits keeping the generators ready for emergency operation. However, the 50-cycle current reduces the operating speed of all synchronous and induction motors to five-sixths that on 60-cycle current. Slower press speeds and timing cycles must be anticipated. Many motors, such as those operating vacuum pumps, compressors. and temperature-control units, are already overloaded on 60-cycle current. Unless they are also wound for 50-cycle operation, they may draw excessive current and burn out the insulation, shortcircuiting the windings. All motor equipment must be closely watched. If motors start to overheat, the operating load must be immediately reduced by slowing down the presses, reducing the vacuum by partially opening the escape valve, or by adjusting the thermostat on the temperature-control equipment to provide less cooling than normally required.
118. Temperature-control Equipment
a. Some mobile camera and photographic units are equipped with temperature-controlled developing sinks or trays. ( See fig. toi.) These maintain a temperature of 67° F.. by heating or cooling the incoming and circulating water. The equipment consists of a refrigeration unit complete with condenser and air-circulating fan, an electrical heating unit, thermostatic controls, heat-interchange cham-
138
her to heat or cool the circulating water, and a circulating pump.
b. Other mobile sections have complete interior temperature control to maintain an efficient operating condition within the vehicle body. All temperature-control equipment is delicate and must be carefully adjusted and serviced for satisfactory operation. 1 his includes precautions against damage from dust, sand, shock, overloading, and freezing weather. In cold climates, continued heating of the vehicle interior ma\ be necessary both during operation and while inactive or in transit. This prevents freezing of the water and solutions and maintains the press and other units at operating temperature. It also prevents moisture condensing on and corroding cold equipment. A gasoline-burning heater installed in each vehicle supplies 25,000 btu per hour, ordinarily enough for operation in temperatures as lbw as 40° F. For operation, maintenance, and repair of the heating units, see TM 5-9170.
I 19. Improvised Equipment and Supplies
Shortages of equipment or supplies frequently make substitutions necessary. Suggested expedients are described below.
<7. Process Camera, if the current supply or arc lamps fail, daylight can be used for exposing the copy. 1 he negatives are taped to the vacuum back with strips of self-adhesive tape to hold them fairly flat during exposure.
b. Plate Processing. Albumen can be replaced by the whites of fresh eggs, casein, condensed milk, or synthetic substitutes. Allowance must be made for their nature by adjusting the coating and exposure operations.
c. Gum Arabic. Gum-arabic solution can be replaced by albumen, glue, starch (dissolved in hot water forming a light paste), or a mixture of these. Satisfactory commercial products are also available.
- — ~ V-.t.Y.?—r r;- . .......
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I IMi flBHBEM fcr'F Ml-JMr.'.-
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I MBtilMEEi IL Jfl CAMERA
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M TEMPERATURE-
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’ RU E^^overelo '1 So
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Figure 101. Mobile-camera darkroom (rear panels open).
139
CHAPTER 11
MAP STORAGE AND DISTRIBUTION
120. Storage Conditions
a. Characteristics of Storage Space. The space selected for storing finished maps should have the following characteristics.
(I) Uniform cool temperature.
(2) Adequate ventilation.
(3) Uniform humidity.
(4) No exposure to drafts or direct heat.
(5) No chemical fumes.
(6) No rodents and vermin.
(7) No strong light.
b. Preventing Deterioration. Since paper is a hygroscopic organic material, it deteriorates, oxidizes. and decays the same as wood. The inherent acidity and moisture content of paper speeds up deterioration. Little can be done to alter the basic acidity of the finished maps. However, moisture content and deterioration are reduced by storing in a dry place. Maps retained for future overprinting are stored separately in a humidity comparable with that in the pressroom. To further protect against deterioration, maps are wrapped or boxed in conveniently handled packages, preferably in the two-ream containers in which the map paper was furnished. Added waterproof wrapping and sealing reduce damage if storage conditions are damp or vermin are present.
c. Method of Storing. Packaged maps are identified on their edges and placed in the storeroom according to a reference system so they can be located quickly. Maps are stacked on skids, platforms. or shelves to keep them off the floor. Since a pile of 20- by 22j4-inch maps 6 feet high weighs about 1.000 pounds, and a similar stack of 22- by 29-inch maps weighs about 1,400 pounds, the supporting platforms or shelves and the floor in the storage building must be strong enough to support the load. Maps for immediate distribution are stored flat on shelves, using an individual marked compartment for each different map subject. The location is keyed to a classification index, either alphabetically or for ready accessibility according to their possible frequency of issue.
121. Distribution
a. Small Quantities. Small quantities are supplied folded or rolled, folding being preferred ii permitted by the using organizations.
(1) Folding. Folding follows the standard size and direction of folds established for each type of map. For small quantity distribution, folding .an be done by hand, marking the location of the folds on the table top or a cardboard overlay. Then the edges are carefully matched and the maps creased with a rounded-edge strip of hard wood. If considerable folding is to be done, a commercial folder should be requisitioned. The folded maps can be supplied in manila envelopes or wrapped in packages with waterproof paper, using internal cardboard reinforcements at the top and bottom of each group of maps.
(— ) Rolling. If folding is not permitted, maps are rolled around a cardboard tube and covered with a sheet of kraft paper. A final covering of waterproof kraft paper is brought over the ends and sealed with tape. If necessary, the tube is painted or dipped into a waterproof sealing compound.
b. Large Quantities. To ship large numbers of maps, the two-ream waterproof containers in which the map paper is originally supplied can be used. Containers are resealed and strapped to assure undamaged arrival. Maps are also shipped in wood boxes lined with a double layer of waterproof wrapping paper. The waterproof paper is sealed at the joints, and the wrapping extended and sealed over the top of the contents before fastening the lid with screws.
c. Identification. Che contents of all map packages are stenciled or marked on the covers, except when security reasons limit identification to a code reference symbol.
122. Destruction
The best way to destroy maps is by burning. However, they must be separated and wrinkled or shredded to let air reach each map or destruction
140
may not be complete. Security conditions seldom permit time for large-scale destruction of storeroom contents by this method. Therefore, large quantities of high-explosive charges and gasoline must be used to completely destroy every map. Storage in for
ward areas must accordingly be limited to minimum quantities anticipated for field requirements. Excessive or superseded maps must not accumulate. They must be sent back regularly to a rear area for storage or destruction.
141
APPENDIX I
SUPPLEMENTAL TABLES
Table XIX.
LENGTH:
1 inch — 2.54 centimeters.
1 foot = 30.48 centimeters.
1 mile = 1,760 yards = 5,280 feet = 63,360 inches — 1.60935 kilometers.
1 centimeter = .3937 inches.
1 meter = 39.37 inches = 3.281 feet.
1 kilometer = 3280.83 feet = .621372 miles.
1 Angstrom =. .001 microns = .000 000 00394 inches.
WEIGHT (avoirdupois) :
1 ounce ~ 437.5 grains = 28.35 grams.
1 pound — 16 ounces = .453'6 kilograms.
1 gram = 15.43 grains = .035 ounces.
1 kilogram = 2.205 pounds = 35.274 ounces.
Weights and measures
CAPACITY (liquid):
1 fluid ounce = 8 drams = 480 minims = 29.57 cubic centimeters.
1 quart = 2 pints = 57.75 cubic inches = .946 liters.
1 gallon = 4 quarts = 231 cubic inches = 3.785 liters.
1 cubic centimeter — 16.23 minims.
1 liter — 1,000 cubic centimeters = 33.815 fluid ounces.
ELECTRICAL:
1 kilowatt (kw) = 1,000 watts = 1.34 horsepower
1 kilowatt hour (kwh) = 1,000 watts for 1 hour = 3415 btu (heat).
1 kilovolt-ampere (kva) = 1,000 volt amperes.
142
Table XX. Temperature conversion
I able XXI. Specific gravity (liquids heavier than zcater)
°F. (degrees Fahrenheit) °C. (degrees Centigrade) °F. (degrees Fahrenheit) °C. (degrees Centigrade) ° B a u mS Specific Gravity °Baum6 Specific Gravity
-40 -40 90 32 0 1.000 21 1.169
-30 -34 95 35 1 1.007 22 1.179
-20 -29 100 38 2 1.014 23 1.189
-10 . ~23 105 41 3 1.021 24 1.198
0 -18 110 43 4 1.028 25 1.208
10 -12 115 46 5 1.036 26 1.219
20 - 7 120 49 6 1.043 27 1.229
30 - 1 125 52 7 1.051 28 1.239
32 0 130 54 8 1.058 29 1.250
35 2 140 60 9 1.066 30 1.261
40 4 150 66 10 1.074 31 1.272
45 7 160 71 11 1.082 32 1.283
50 10 170 77 12 1.090 33 1.295
55 13 180 82 13 1.099 34 1.306
60 16 190 88 14 1.107 35 1.318
65 18 200 93 15 1.115 36 1.330
67 19.5 210 99 16 1.124 37 1.343
70 21 212 100 17 1.133 38 1.355
75 24 220 104 18 1.142 39 1.368
80 27 230 110 19 1.151 40 1.381
85 29 240 116 20 1.160 41 1.394
143
Table XXII. Relative humidity
WET BULB TEMPERATURE °F
dry bulb temperature °F
34 36 38 40 42 44 46 48 50 52 54 56 5 60 62 64 66 68
50 52 54 56 58 5 16 27 9 19 3 12 7 1 38 49 61 74 87 29 40 51 63 75 22 32 42 53 64 16 25 34 44 55 10 18 27 37 46 100 87 100 76 88 100 65 76 88 100 56 66 77 89 10(
60 62 64 66 68 5 13 21 30 39 8 16 24 32 4 11 18 26 7 14 21 3 10 16 48 58 68 78 8( 41 50 59 69 7! 34 43 51 60 71 29 36 44 53 6 23 31 38 46 54 100 89 100 79 90 100 71 80 90 100 62 71 80 90 100
70 72 74 76 78 6 12 3 9 5 3 19 25 33 40 48 15 21 28 34 42 11 17 23 29 36 8 13 19 25 31 5 10 16 21 27 55 64 72 81 90 49 57 65 73 82 43 50 58 65 74 38 44 51 59 66 33 39 46 53 60
80 82 84 86 88 3 7 12 18 23 4 10 14 20 1 7 12 16 5 9 14 3 7 11 29 35 41 47 54 25 30 36 42 48 21 26 32 37 43 18 23 28 33 39 15 20 25 30 35
90 92 94 96 98 1 5 9 3 7 5 3 1 13 17 22 26 31 11 15 19 23 28 9 12 16 20 24 7 10 14 18 22 5 8 12 15 19
100 102 104 106 3 7 10 13 17 1 5 8 11 15 3 7 10 13 5 8 11
108
3
7
10
21
18
16
14
12
36
32
29
26
23
100
91
82
74
67
61
55
49
44
40
70 72 74 76 78
80 82 84 86 88
90 92 94 96 98
100 102 104 106 108
110
(Barometric Pressure 29.92. Air Velocity 600 feet (or more) per minute.)
100
91
82
75
100
91 100
83 91 100
110
112
114
116
118
5 8
4 7
6
11
9
8
7
6
120
122
124
126
34 36 38
40 42 44 46 48
60 52 54 56 58
60 62 64 66 68
68
61
56
50
46
75
69
62
57
51
83
76
69
63
57
91
84
76
70
64
100
92
84
77
70
100
92
84
77
100
92 100
85 92 100
41
37
33
30
27
24
22
20
17
16
14
12
9
8
47
42
38
35
32
52
48
43
39
36
58
53
49
44
40
65
59
54
50
45
71
65
60
55
50
78
72
66
61
55
85
78
72
66
61
92
85
79
73
67
100
92
85
79
73
100
93
86
79
100
93 100
86 93 100
28
26
23
21
19
33
30
27
24
22
37
34
31
28
25
41
38
35
32
29
46
42
39
36
33
51
47
43
40
37
56
52
48
44
41
62
57
53
49
45
68
62
58
53
49
73
68
63
58
54
80
74
69
64
59
86
80
69
64
93
86
80
75
70
100
93
87
81
75
100
93
87
81
100
93 100
87 93 100
17
15
13
12
11
20
18
16
14
13
23
21
19
17
16
26
24
22
20
18
30
27
25
23
21
34
31
28
26
24
38
35
32
29
27
42
38
35
33
30
46
42
39
36
34
50
47
43
40
37
55
51
47
44
41
60
55
52
48
45
65
60
56
52
49
70
65
61
57
53
75
70
66
61
57
81
76
71
66
62
87
81
76
71
67
93
87
82
76
72
100
94
88
82
77
6 9
8
7
12
10
9
8
14
13
11
10
17
15
14
12
19
18
16
15
22
20
18
17
25
23
21
19
28
26
24
22
31
29
27
25
34
32
30
27
38
35
33
30
41
39
36
33
45
42
39
37
49
46
43
40
53
50
47
44
58
54
50
47
62
58
54
51
67
63
59
55
72
67
63
59
70 72 74 76 78
80 82 84 86 88
90 92 94 96 98,100 102 104 106 108
110
144
Table XXIII. Decimal equivalents DECIMAL EQUIVALENTS
FRACTION Inches Mm. FRACTION Inches Mm.
1/64 .016 .40 33/64 .516 13.10
1/32 .031 .79 17/32 .531 13.49
3/64 .047 1.19 35/64 .547 13.89
1/16 .063 1.59 9/16 .563 14.29
5/64 .078 1.98 37/64 .578 14.68
3/32 .094 2.38 19/32 .594 15.08
7/64 .109 2.78 39/64 .609 15.48
1/8 .125 3.18 5/8 .625 15.88
> 9/64 .141 3.57 41/64 .641 16.27
5/32 .156 3.97 21/32 .656 16.67
11/64 .172 4.37 43/64 .672 17.07
3/16 .188 4.76 ■—— 11/16 .688 17.46
13/64 .203 5.16 45/64 .703 17.86
7/32 .219 5.56 23/32 .719 18.26
15/64 .234 5.95 47/64 .734 18.65
1/4 .250 6.35 3/4 e .750 19.05
17/64 .266 6.75 • 49/64 .766 19.45
9/32 .281 7.14 25/32 .781 19.84
19/64 .297 7.54 51/64 .797 20.24
5/16 .313 7.94 13/16 .813 20.64
21/64 .328 8.33 53/64 .828 21.03
11/32 .344 8.73 27/32 .844 21.43
23/64 .358 9.13 7/8 55/64 .859 21.83
3/8 .375 9.53 .875 22.23
25/64 .391 9.92 57/64 .891 22.62
— 13/32 . 406 10.32 29/32 .906 23.02
27/64 .422 10.72 59/64 .922 23.42
7/16 .438 11.11 15/16 .938 23.81
29/64 .453 11.51 61/64 .953 24.21
15/32 .469 11.91 31/32 .969 24.61
31/64 .484 12.30 1 63/64 .984 25.00
1/2 .500 .12.70 1.000 25.40
145
Table XXIV. Summary of reproduction methods
Time required for first print1 (hours) Impressions per hour Maximum number of impressions per plate Quality of reproduction Types of reproduction Printing colors
Offset-lithography. . M to 2 3,000-5,000 50,000-100,000 Good-excellent Maps, mosaics, forms. 1 to 62 or more
Gelatin duplicator. 25-100 Poor Overprints, instructions. Purple and others 3
B&W 20-40 Unlimited Fair Single-color positive photoprints of maps, sketches. Purple or others
Ammonia process. . M 60-120 Unlimited Fair-good Same as B&W Purple or others.
Brownprint 20-40 Unlimited Fair Negative photoprints, proofs. Brown
Blueprint 15-30 Unlimited Poor Negative photoprints. Blue
Stencil duplicating. 2,000-12,000 400-5,000 Poor Typewritten instructions, sketches. Black or other colors 2
Photographic Rapid projection 30-60 Unlimited Excellent Photoprints, mosaics. Black
printer 500-1,500 Unlimited Excellent Photoprints, mosaics. Black
1 Minimum times with materials and solutions available. Corrections and art work additional.
2 Printing colors are inks. Additional colors by re-runs.
3 Several colors can be printed simultaneously.
146
APPENDIX I I
GLOSSARY
Abrasive. Hard material used for cutting away softer materials. Used in plate grinding to grind into and provide plate with matte surface. (See par. 71.)
Acetic acid, CH3COOH. Glacial is over 99 percent pure. 28 percent made by diluting 3 parts glacial acetic acid to 8 parts water. Used as counteretch in plate processing, also a short stop to neutralize alkaline developers in negative before fixing.
Aerosel. A commercial wetting agent. Issued in 10 percent concentration. (See Wetting agent.)
Albumen. Dried white of eggs; 1 part equals 7 to 8 parts of liquid egg white. Decomposes in moist air. Used in albumen process of platemaking and as substratum in wet-plate coating.
Albumen process. A method for making photolithographic press plates. (See par. 79.)
Alcohol, ethyl, C2H-OH. Volatile liquid solvent. Used in wet-plate collodion, and as plate cleaner for gum-reversal plates. Anhydrous alcohol is water-free alcohol.
Alcohol, methyl, CH.SOH (methanol) (wood alcohol.) Toxic, may cause blindness. Used as cheap solvent in place of ethyl alcohol.
Alkali. Solution containing free hydroxyl ions. Alkalis and acids neutralize each other to form salts. Alkalis swell colloids. They are used in photographic and plate processing developers.
Alum (potassium alum) (aluminum potassium sulfate) A1K(SO4)2. Salt used to toughen colloid films in photography and as ingredient in preparing lithographic plates for hand drafting.
Aluminum oxide (alumina) A12O3. An exceedingly hard crystalline powder used as abrasive in plate graining. Numerically graded by sieve mesh (openings per square inch) that particles will just pass through.
Ammonia process. See Diazo compounds.
Ammonia water (ammonium hydroxide), NH3OH.
Issued as 28-29 percent ammonia gas (NIL.) dissolved in water. Strongly alkaline. Used to alkalize plate-processing sensitizers and to soften exposed sensitizer for development.
Ammonium bichromate (ammonium dichromate), (NH4)2Cr2O7. Orange-red crystal used to make plate-processing colloids sensitive to light. Also for photographic reversal solutions in direct' positive making.
Anastigmat (without astigmatism). Describes lens corrected for minimizing image distortion.
Angstrom unit (A0) (io-8 cm= .000 000 00394 inches). A unit of measure primarily applied to light waves.
Anhydrous (anhy). Describes chemicals from which water is completely removed.
Apochromat. Describes a color-corrected lens designed to minimize distortion in the specific ranges used in color-separation work.
Asphaltum (mineral pitch). Issued as a water-in-soluble solution. Used as a protective coating in plate processing. (See par. 79.)
Astigmatism. Image distortion resulting from incompletely corrected lenses. (See par. 33.)
B&W (black and white). A direct positive printing process for obtaining duplicate prints from transparencies. Utilizes a diazo-compound sensitized paper. Requires contact with alkaline solution for development.
Baume. A unit for measuring density of liquids. (See table XXL)
Bearers. Bands on ends of press cylinders that roll in contact with each other and maintain correct separation between cylinder surfaces.
Benzene (benzol) C6H6. Highly volatile and inflammable coal-tar byproduct. Used as solvent and thinner for rubber cement.
Benzine (naphtha). Highly volatile and inflammable fractions of petroleum. Used as solvent in washing-up blanket and press.
Blanket dust. A half-and-half mixture of French chalk and powdered sulfur dusted on offset press blanket to remove its tackiness.
Blanket, offset. A rubberized blanket on a fabric base. Strapped around blanket cylinder of offset press. Receives inked impression from plate and transfers it to paper. (See par. 90.)
147
Bleeding. Spreading or running of ink or other soluble materials.
Blind. A visible printing image that will not accept ink.
Blocking. Adhesion between paper sheets preventing paper feeding in press.
Blue-line. A photographically prepared image in blue lines for guiding location of additional work in map color separation. (See pars. 29 and 82.)
Body gum. A thick gummy product resulting from prolonged boiling of linseed oil. Used to stiffen lithographic inks.
Boric acid, H3BO3. A preservative and antiseptic. Used in fine-grain photographic developers.
Bromide. Refers to photographic sensitive materials containing silver bromide salts.
Bromide process. Method for making photographic contact prints from opaque copy. (See par. m.)
Brownprint (vandyke paper, silverprint paper). Photographic printing paper coated with lightsensitive iron and silver salts for obtaining browncolored paper negatives directly on exposure through transparencies. Also used for obtaining proof copy from negatives because exposure makes visible image without further processing. (See par. 109.)
Buffer. A chemical agent added to a solution to stabilize it against rapid break-down. Used in offsetpress fountain solutions to maintain constant pH.
Calcium chloride, CaCl2. Hygroscopic crystals. Used in gum-reversal process as an inert vehicle to carry the active agents.
Camera. An optical device for projecting an image of an external subject onto a photographically sensitized negative inside a lightproof box.
Canada balsam. Sap of fir tree having approximately same refractive index as glass. Used as cement to join lens elements and halftone screens.
Carbon arcs. Intense light source produced by passing high current across a carbon arc gap. Used in camera-copy illumination and for exposure of press plates.
Carbon tetrachloride, CC14. Volatile noninflammable solution. Used as a cleaning fluid.
Cartographic. Refers to materials used for mapping.
Cartographic film. A low-shrink-base film used for map negatives. (See par. 44.)
Casein. A colloid prepared from milk. Used as substitute for albumen in plate processing; also as binder in manufacturing paper.
Catch-up. Press plate accepts ink in nonprinting areas, usually because of insufficient water.
Caustic soda. See Sodium hydroxide.
Citric acid, CcH8O7. Mild acid used for developing and cleaning gum-reversal press plates.
Cobalt drier. Fast ink drier usually used for singlecolor and black printing. Provides a hard dry surface that resists wear and rubbing. Not suitable where overprinting in other colors must follow. Made of cobalt resinate or linoleate ground in a varnish.
Collodion. A solution of nitrocellulose in alcohol and ether. Used with iodizer to form emulsion in wet-plate photography. (See par. 52.)
Colloid. Solution containing suspension of undissolved particles too minute to precipitate. Egg albumen, gelatin, glue, gum, and similar substances used in photolithography are colloids. When these colloids are in solution with a bichromate, they can be coagulated by exposure to light.
Collotype. A gelatin printing process in which inkreceptivity of printing plate is proportional to amount of tanning on exposure to light.
Coma. Lens distortion resulting in oblique rays through lens focusing at different points on same plane to appear comet shaped.
Compound. Ingredient added to ink to give it desired working properties.
Consistency. Classification of the working properties of an ink, including effects of viscosity, tack, and body.
Counter-etch. Process of cleaning a lithographic press plate by use of a diluted acid to remove oxides and prepare it for receiving the printing image.
Dampeners. System of rollers for applying a film of moisture to lithographic printing plate.
Deep etch. Lithographic printing plate prepared with printing areas slightly recessed below grained surface of plate.
Density. A measure of opacity of a photographic film to light.
Desiccated (des). Chemical salts with water removed.
Developing ink. A greasy ink applied to the exposed albumen image to make the ink-attracting printing design visible when developing the exposed press plate. (See par. 4.)
Development. Chemical process for bringing out image on photographic materials exposed to light.
148
Diaphragm. Opening in lens to control quantity of light passing through. Iris diaphragm is adjustable to vary the light transmitted.
Diaphragm control. A device for controlling adjustment of diaphragm opening to maintain uniform light intensity on negative for different lens locations. (See par. 35.)
Diazo compound. Dye compounds that are sensitive to light. Exposure decomposes the compound, preventing dye-coupling. Remaining unexposed compound forms color when exposed to ammonia fumes or alkaline solutions. (See pars. 107 and 108.)
Diffraction. The bending and resulting interference of light around the edges of small openings. This will appear as bands or fringes of light resulting from the alternate additive and subtractive combination of the light waves. The diffraction theory of halftone negative making is based on this phenomenon. (See par. 35.)
Dope. An ingredient added to a lithographic ink in the pressroom, purported to give it special properties or to adjust the ink to conditions of operation.
Dot-etching. Reducing dot size on halftone negatives by etching with a silver solvent. (See par. 62.)
Double-shooting. The exposure of two prints in succession and in register on the same area of the press plate. (See par. 66.)
Drier. A compound added to a printing ink to accelerate the drying of its oils. (See Paste drier and Cobalt drier.)
Ductor. Press rollers that have reciprocal as well as rotary movement, used to control the transfer of ink or water from the fountain roller to the distributor roller by alternately contacting each.
Emboss. Absorption of vehicles from ink resulting in rubber blanket swelling to form relief image of printing design. If not excessive, will disappear on washing and hanging blanket so solvents evaporate.
Emulsion. A suspension of fine globules of oil in water (such as milk). Photographic emulsions are a suspension of fine light-sensitive salts in gelatin or other colloids.
Emulsify. Destructive absorption of excessive water by ink resulting from use of too much drier or water, too little acid, or a poor ink. (See par. 9i.)
Etch. Chemical treatment of plate to make nonprinting areas grease-repellent and water-receptive.
Exposure. The quantity of effective light necessary to complete the chemical or physical change that results in full and correct development of the image.
Extender. A white or colorless pigment mixed with ink to improve working properties or reduce color intensity. Also used to extend quantity or covering power of ink.
Extension. The distance between the lens and the negative surface. (See par. 33.)
Farmer’s reducer. See Reducer.
Felt (smooth side). The top side of paper in process of manufacture that is contacted by felt belt for extraction of moisture.
Film. A thin coherent layer of material. A photographic negative prepared on a sheet plastic base. (See par. 44.)
Filter. A material that selectively witholds one class of material or energy while permitting another to pass. In plate-processing, the use of a cotton or cheesecloth pad to permit the dissolved colloids to pass, holding back other insoluble or foreign materials. Photographically, a colored film or glass that transmits a single color or a range of colors while absorbing the others. (See par. 34.)
Filter factor. Ratio of increased exposure time required when using a selected filter with a particular negative emulsion. (See par. 34.)
Fix. To stabilize the developed photographic negative by removing unexposed silver salts in emulsion using hypo (sodium thiosulfate).
Flash. In halftone negative making, the supplementary exposure with a small stop opening to a white sheet of paper placed over copy to form a uniform fine dot over entire negative, irrespective of subject detail. (See par. 48.)
Focus. The plane of a lens or optical system in which the image is of maximum sharpness. (See par- 33-)
Fog. The veil or cloudiness on transparent areas of negative that prevents complete passage of light.
Form rollers. The ink and dampener rollers on the offset press that contact the press plate.
Formalin. A solution of formaldehyde gas (HCHO) in water (37—40 percent. A powerful reducing agent used as a preservative and a hardener for photographic emulsions.
149
F ountam. Carries the reserve of ink or water required for printing on the offset press.
French chalk. See Magnesium silicate.
Fulling. 1 he separation of photographic emulsion from its base along the edges of the negative.
Fungicide. A chemical used to prevent deterioration of organic materials, such as albumen, gum arabic, and gelatin, by preventing growth of fungi. The fungi are parasitical plants living off organic materials and include mushrooms, smuts, molds, and mildews.
Gamma. A measure of the contrast of the negative. (See par. 44.)
Geai streaks. Parallel tint streaks appearing across printed sheet at same interval as gear teeth on cylinder. Caused by improper underpacking or defective press conditions resulting in difference of surface speed between cylinders and pitch diameter of gears.
Gelatin. Organic colloid; swells in cold water; dissolves in hot water.
Glass. Crown glass is a soft glass with a low index of refiaction (1.50 to 1.55). Flint glass is harder with higher index of refraction (1.55 to 1.94). Color-corrected lenses are made by combining glasses of different refractive indices to neutralize color distortion. (See fig. 6.)
Gradient tints. A range of color tints to represent varying elevations on a map.
Gram. Direction of alignment of fibers acquired by paper in process of manufacture. (See par.
91.) Also refers to relative particle size of silver grain in negative emulsion.
Grid. A pattern of rectangles formed of parallel lines for referencing locations on a map.
Guides. Mechanical stops used in positioning paper sheet on press.
Gum atabic (gum acacia). A dried sap of acacia trees. Soluble in water. Used to form a protective and ink-repellent film on the lithographic printing plate.
Halftone. Reproduction of a continuous-tone copy into a gi id of fine dots of varying sizes to present appearance of continuous tone on printed sheet. (See par. 35.)
H ectographic. Materials used for printing with gelatin duplicator. (See par. 106.)
High light. Lightest areas on copy (darkest on negative).
High-light negative. Haltone negative exposed to block out the high-light dots without altering the
tone gradations of the subject. Reduces retouching.
humidity. A measure of moisture content of air. Relative humidity is percentage of moisture in air at a specified temperature relative to maximum moisture air can hold at that temperature (See table XXII.)
I~i yd) ochloric acid, HC1. An acid used in cleaning (counter-etching) lithographic press plates.
FIydr0gen ion concentration (H). A measure of degree of acidity or alkalinity of a solution. It is equal to the logarithm of the reciprocal of the excess of hydrogen ions in an acid solution, or the hydroxyl ions in alkaline solutions. (See par. 90.)
Hydrometer. Instrument for measuring density of liquids by distance a projecting graduated scale floats above surface of the liquid.
Hydroquinone, C6H4(OH)2. A reducer used in photographic developer.
Hygrometer. Instrument for measuring relative humidity of air. (See par. 79.)
Hypo. See Sodium thiosulfate.
Imp) cssion. Inked image received by paper sheet in press.
Inertia. Measure of minimum quantity of light required in exposure of photographic emulsion to cause reduction of silver upon development.
Infrared. A range of radiation extending beyond the red end of visible spectrum. Includes heat rays.
Ink. A composition of pigments, vehicles, and compounds or greasing agents providing a stiff ink for lithographic printing. (See par. 91.)
Intensification. Chemical treatment to increase contrast and density in a negative. (See par. 50.)
Jog. Jarring paper to align and stack uniformly in a pile.
Lactic acid. Organic acid obtained from milk and other materials. Used as mild acid in deep-etch plate processing.
Lay. Correct positioning of subjects on press plate or printed sheet.
Layer tints. {See Gradient tint.)
Lay-out. The arrangement of printing subjects on press plate or printed sheet. (See par. 63.)
Lens. A process lens is a system of optical glass elements designed to project an image of a subject or copy on a photographically sensitized material. (See par. 33.)
150
Line negative. A negative of a drafted or printed copy prepared on photomechanical film. (See par. 47.)
Dinseed oil. Oil obtained from seed of flax plant. A drying oil used in mixing inks. Boiled oils are called varnishes. {See Varnish.)
Lithography. A planographic process of printing using the mutual repulsion between oil and water to control the ink-receiving design areas. (See Par. 5.)
Divering, ink. Permanent stiffening or coagulation of ink on standing, rendering it unsuitable for use.
Long ink. Ink that can be drawn into long strings. Lye. See Sodium hydroxide.
Magnesium nitrate, Mg(NO3)2. A salt used as a buffer in fountain etches.
Magnesium silicate, Mg3Si4O1:1. (French chalk). Used in powdered form to dust inked imaged in plate processing, or in combination with powdered sulfur as a blanket dust.
Make-ready. Materials and process for underlaying localized areas or entire printing plate to provide correct printing pressure.
Mass-tone. Color of ink in mass. May differ from printed color.
Negative. A record of a photographic image retained on a film and used for reproducing duplicate prints of image.
Nitric acid, HNO;i. A strongly corrosive acid used diluted as a glass cleaner in wet-plate making, and sometimes in counter-etch solutions.
Offset. Reproduction from lithographic plates in which inked image is printed on rubber blanket that in turn prints or offsets it onto sheet of paper. Also used to describe unwanted transfer of ink to back of sheet from next lower sheet in pile.
Opacity. A measure of degree a material or negative prevents passage of light. (See par. 44.)
Opaque. A paste ink used to block out areas of negatives to prevent these areas printing through onto the press plate. (See par. 60.)
Orthochromatic. Photographic emulsions sensitized to violet-yellow portion of color spectrum. (See par. 44-)
Oxidation, Corrosion of press plates due to slow drying. If severe, oxidation spots accept ink and plate cannot be used. (See par. 73.)
Panchromatic. Photographic emulsions sensitive to entire visible spectrum of color. (See par. 44.)
Paraformaldehyde (trioxy methylene). Powder that liberates formaldehyde in solution. Used in photomechanical developers.
Paste drier. Drier used principally for colored inks. Dries ink uniformly and slowly without hard surface to enable overprinting of subsequent colors. Consists of lead and manganese resinates or linoleates ground in a varnish.
pH. See Hydrogen ion concentration.
Phosphoric acid. H.,PO4. Issued in 85 percent concentration. Used in plate etches and press-fountain solutions.
Photography. A process for recording and duplicating images by exposure to light.
Photolithography. Process for preparing lithographic plates by selective exposure to light. (See par. 6.)
Photomechanical. Materials used in photographic reproduction by printing methods.
Photomosaic. Assembly of aerial photographs of small coverage to form composite picture of larger area.
Pigment. Ingredient in ink to give it color, body, and opacity.
Pitch diameter. Rolling diameter of a gear. On offset press, same diameter as cylinder bearers.
Planography. Printing from flat plate in which lithographic properties separate printing from nonprinting areas.
Plucking. Lifting of surface fibers of paper sheet by ink having excessive tack.
Plugging. Filling in of shadow dots on negative or in printing.
Polymerize. Chemical combination of organic compounds in irreversible action.
Potassium bromide, KBr. Salt used in photographic developers to inhibit fog.
Potassium cyanide, KCN. Salt used in solution for wet-plate reduction, also for local removal of albumen image.
Potassium ferricyanide, K3Fe(CN)G. Used in preparing photographic reducers and blueprint solutions.
Power factor. Proportion of reduced electrical power resulting from inductive lag of current behind voltage.
Ream, Quantity of paper, 480 sheets, usually 500 sheets.
151
Reduction (photographic). A chemical process resulting in decomposing exposed silver salts into metal silver and byproduct.
Refraction. Bending of light in passing from one transparent material to another at an angle.
Register. Agreement in location of successively printed images.
Reproduction. Duplication of subject or copy by photographic or printing methods.
Reticulation. Break-up of gelatin emulsion on negative into wormlike pattern, usually due to temperature changes or excessive hardening and drying in processing.
Roll-up. A greasy black ink used for rolling-up lithographic plates with a hand roller to work up a good printing foundation.
Scum. Film of ink accepted by nonprinting areas of plate.
Sensitizer. The light-sensitive solution applied to lithographic plates. (See par. 6a.)
Sensitometry. Light-sensitive characteristics of photographic materials.
Short ink. Ink of low elasticity and high pigment content that cannot be pulled into strings.
Silver bromide, AgBr. Silver salt sensitive to light. Used in photographic emulsions.
Silver chloride, AgCl. Sensitive salt used in paper emulsions.
Silver nitrate, AgNO3. Used in sensitizing wet-plate negatives. (See par. 79.)
Slip sheets. Sheets of paper manually placed between printed sheets delivered by the press to prevent offsetting of ink.
Sodium benzoate, NaC7H5O2. Preservative for organic materials.
Sodium bicarbonate, NaHCO3. Weak alkali used to assist press-plate development.
Sodium carbonate, Na2CO3. Accelerator for photographic developers.
Sodium hydroxide, NaOH. Powerful alkali used in solution to remove old images from press plates.
Sodium sulfite, Na2SO3. Preservative for photographic developers.
Sodium thiosulfate (hypo), Na2S2O3. Used for dissolving undeveloped silver salts.
Specific gravity. Ratio of density of a material to water.
Spherical aberration. Lens distortion in which light from outer zone of lens does not focus in same plane as light from inner zone.
Staging. Protecting negative areas from etch in dot-etch control.
Stripping. Refusal of press rollers to accept ink, caused by glazing or driers.
Sulfur, S. See Blanket powder.
Tack. Stickiness of ink. Property enabling ink to adhere to paper and trap succeeding printing inks. First color usually has most tack and least paste drier. Each succeeding color is progressively less tacky and has more paste drier. Last color has least tack and uses cobalt drier to provide hard-finished surface.
Talcum powder. See Magnesium silicate.
Tan. Rendering colloids insoluble by chemical or light action.
Thixotropy. Property of inks evidenced by temporary softening or lowering viscosity when stirred or worked.
Tint. A comparative lighter shade of color. A form of scum appearing uniformly on litho plate, resulting from emulsification of ink and other causes.
Transmission. Percentage of light permitted to pass through a translucent or transparent material.
Trap. Ability of ink on paper to accept following printing color. (See Tack.)
Trisodium phosphate. Used as cleaning agent and rust inhibitor in plate-graining.
Tusche. A liquid ink used for drafting printing areas on lithographic plates.
Under chitting. Action of light or acids in undermining the edges of fine lines or halftone dots in plate processing or on the press.
Varnish. Usual lithographic vehicle for inks. Prepared by boiling linseed or other drying oils. (See Linseed oil.) Varnishes are numbered from No 0000 to No 8, or higher, corresponding to their increasing viscosity resulting from extended boiling. No 8 varnish is frequently called “body gum.” (See par. 91.)
Vehicle. Liquid used to hold pigments together and give ink its working properties. (See Varnish.)
Viscosity. Measure of resistance of a fluid to motion.
Washout. Removal of ink from printing areas of press plate and replacing it with an ink-receptive asphalt or other varnish that can be redissolved.
Wet-plate. A photographic negative, prepared in the darkroom, that must be exposed and processed while wet. (See par. 52.)
152
Wetting agent. Chemicals that facilitate mixing of solids with liquid by lowering surface tension. Used to promote uniform wetting and drying.
Whirler. Equipment used for applying sensitizer to press plate. (See par. 75.)
Winding stock. Separation of paper stock by jogging and flexing to ventilate or get air between the sheets.
Yield value. Measure of rigidity of ink.
153
APPENDIX III
REFERENCES
TM i 219, Basic Photography.
TM 5-230, Topographic Drafting.
TM 5-4420, Grainer, Plate, Litho Offset, Zarkin 33" x 62".
TM 5-5044, Generator, 5 kw, no-volt, i-phase, Onan.
TM 5-6000, Camera, 24" x 24" Monotype.
TM 5 6006, Camera, Copying, Rutherford 24" x 30".
TM 5-6020, ATF Webendorfer Big Chief 29" Offset Press.
TM 5-6022, Harris-Seybold-Potter 20" x 22J/Z Press.
TM 5-6040, Camera, 24" x 24" Rutherford.
TM 5-6042, Vacuum Printing Frame, Pitman AF IOI.
TM 5-6044, Whirler, Litho Offset 22-%" x 23", Pitman.
TM 5-6046, Printing Lamp, Macbeth, 12-B-1-25, Airflow.
TM 5-6050, Camera, Vertical, Huebner, 10" x 10".
TM 5-6054, Vacuum Printing Frame, Pitman AF 103.
TM 5-9170, Heater, Gasoline Burning, Hunter Model UH-3.
AR 300-15, Military Maps and Mapping.
A.M.S. Bulletins (restricted periodical) Army Map Service, 6101 MacArthur Blvd., Washington, D.C.
Clerc, L. P., Ilford Manual of Process Work, Ilford Limited, London, England.
Ellis, Carleton, Printing Inks, Reinhold Publishing Corp., 330 W. 42nd St., New York, N.Y.
* Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., 1900 W. 112th St., Cleveland, Ohio.
*Kodak Wratten Light Filters, Eastman Kodak Company, Rochester, N.Y.
*Kodak Reference Handbook, Eastman Kodak Company, Rochester, N.Y.
Lester, Henry M., Photo-Lab-Index, Morgan & Lester, 101 Park Ave., New York 17, N.Y.
Lithographers’ Journal (periodical), 450 Seventh Ave., New York 1, N.Y.
♦Lithographers’ Manual, Waitwin Publishing Co., 1776 Broadway, New York, N.Y.
Lithographic Technical Foundation (complete series of publications), 131 East 39th St., New York, N.Y.
Mertle, J. S., Process Photography and Plate Making, G. Cramer Dry Plate Co., Shenandoah & Lemp Ave., St. Louis 4, Mo.
Modern Lithography (periodical), 254 W. 31st St., New York 1, N.Y.
National Lithographer (periodical), 11 Park Place, New York, N.Y.
Neblette, C. B., Photography, Its Principles and Practice, D. Van Nostrand Co., Inc., 250 Fourth Ave., New York, N.Y.
♦Polk, R. W., Practice of Printing, The Manual Arts Press, Peoria, Ill.
♦Sayre, I. FL, Photography & Platemaking for Photolithography, Litho Textbook Publishing Co., 30 W. Washington Blvd., Chicago 2, Ill.
Sayre, I. H., Single Color Offset Press, Lithographic Textbook Publishing Co., 30 W. Washington Blvd., Chicago 2, Hl.
Wolfe, H. J., Printing and Litho Inks, MacNair-Dorland Co., 254 W. 31st St., New York, N.Y.
Map Reproduction Equipment Manufacturers
Addressograph-Multigraph Corp., 1200 Babbitt Rd., Cleveland, Ohio.
Multilith press.
American Type Founders, 200 Elmora Ave., Elizabeth B, N. J.
ATF Webendorfer press.
*ASF Catalog, ENG 5.
154
Challenge Machinery Co., Grand Haven, Mich.
Paper cutter.
Davidson Mfg. Corp., 1020 W. Adams St., Chicago
7, Ill.
Portable press.
Dayton-Acme Co., 930 York St., Cincinnati, Ohio. 20" x 24" printer.
Douthiit Corp., 650 W. Baltimore Ave., Detroit 2, Mich.
Diaphragm control, temperature-controlled sink.
Elwood Pattern Works, Indianapolis, Ind.
Enlarger.
Garraway Research & Products Co., Rutherford, N. J.
Rapid projection printer.
Gelb, Joseph, Co., 12 E. 32d St., New York 16, N. Y.
Camera lamps.
Goerz American Optical Co., C. P., 317 E. 34th St., New York 16, N. Y.
Lenses.
Harris-Seybold-Potter Co., 4510 E. 71st St., Cleveland 5, Ohio.
Harris press.
Huebner Laboratories, 305 E. 46th St., New York 17, N. Y.
Vertical camera.
Hunter & Co., 1550 E. 17th St., Cleveland, Ohio. Vehicle heater.
Industrial Timer Corp., 117 Edison Place. Newark
5, N. J.
Electric timer.
Lanston Monotype Machine Co., 24th & Locust St., Philadelphia 3, Pa.
Camera, Whirler.
Macbeth Arc Lamp Co., 875 N. 28th St., Philadelphia 30, Pa.
Camera and printing lamps.
McCabe-Powers Auto Body Co., 5900 N. Broadway, St. Louis 15, Mo.
Truck body.
Morse Instrument Co., Hudson, Ohio.
10" x 10" contact printer.
Novadel-Agene Corp., Belleville, N. J.
Temperature-control trays.
Ozalid Products Division (General Aniline & Film Corp.), Johnson City, N. Y.
Ammonia process machine.
Peck & Harvey, 4327 W. Addison St., Chicago, Ill. Photo dryer.
Pitman, Harold M., Co., mo—13th St., North Bergen, N. J.
Vacuum frame, Whirler.
Rutherford Machinery Co., 100 Sixth Ave., New York 13, N. Y.
Camera, task force equipment.
Temprite Products Co., Detroit, Mich.
Temperature-controlled trays.
Universal Cooler Corp., 333 Mary St., Marion, Ohio. Air conditioning unit.
Wendel, Peter & Sons Inc., 464 Coit St., Irvington, N. J.
Truck body.
Zarkin Machine Co., 335 E. 27th St., New York 16, N. Y.
Plate grainer.
155
INDEX
Albumen process (table XIII) Ammonia process ..............
Arc lamp .....................
Asphaltum sensitizer .........
Paragraphs
.6a, 77-80, 87 .105
.32, 79g, 119a
Ad
Page
3, 74, 80
113
25, 75, 139
4
B&W process.................................................................107 122
Bibliography ...............................................................App II 147
Bimetal plates .............................................................6d 4
Blanket, offset ............................................................7, 90 5, 88
Care ...................................................................102d 111
Mounting ...............................................................95 96
Blue lines .................................................................29, 82, 87/ 23, 77, 80
Blueprint ..................................................................119 124
Bromide process ............................................................Hl 124
Brownprints ........................................................................................................199 66, 123
Camera .....................................................................4a, 30 1, 24
Copyboard ..............................................................31, 475 24, 47
Focusing ...............................................................33c, 47c, f 28, 47
Ground glass ...........................................................37 37
Lamps ..................................................................8a, 32, 79 g, 119a 5, 25, 75, 139
Lens ...................................................................33 25
Operation ...............................................................46-55 46
Task force .............................................................113 127
Vacuum back ............................................................38 37
Catch-up .......................................<•..........................103a 112
Collotype ..................................................................bd 4
Color:
Filters (table VIII) ...................................................8a, 24a, 34, 36, 53 5, 21, 32, 36, 50
Map ....................................................................8, 9, 18 5, 9, 16
Safelights ............................................................. 42 38
Theory..................................................................-8a 5
Color separation:
Blue line ............................'.................................29 23
Exposure................................................................31c 25
Hand-drawn .............................................................28, 60a 22, 60
Masking method .........................................................25, 315, 605, 63, 76c 21, 25, 60, 63, 74
Company organization........................................................12 10
Contact printing ...........................................................-55c 54
Copy .......................................................................18 19
Corrections ............................................................19, 24 17, 21
Drawing materials .......................................................20-23, 29 18, 23
Preparation ............................................................13, 16, 17, 19, 315, 57 10, 14, 16, 17, 25, 59
Reference marks ........................................................ 27 21
Stick-ups .............................................................. 26 21
Darkroom ....................................................................30
Equipment ...............................................................43
Illumination ............................................................-42
Portable.................................................................H3
Decimal equivalents. (See table XXIII.)
Deep-etch process (table XV) ................................................6c, 86, 89
Densitometer ................................................................41
24
39
38
127
4, 79, 81
38
157
Paragraphs
Developer ..........
Formulas .......
High temperature Diaphragm control . . Dot etching ...........
Double exposure:
•44b
56
.56a
.47g, 33b, c, 35c, 48c, 49
.62
Negatives ...............................................................66
Press plates ............................................................59b
Drawing materials : Aids .........................................................................90, 61
Bromide prints ...........................................................23
Metal-mounted paper .....................................................21
Sprayed lacquer plates ..................................................22
Driers, ink .................................................................914
Electrical equipment ........................................................38, 117
Engraving....................................................................61
Etching, plate ..............................................................65, 797, 87c
Exposure meter ..............................................................41. 854
Farmer’s reducer .........
Feeder, press ............
Adjustment ...........
Filters, color (table VIII)
Fixer ....................
.56/
,90c
.98
.8a, 24a, 34, 36, 53
.445, 47/, 487, 56(7,c
Fountain solution :
Control .......................................................................905, 97
pH ............................................................................90c, 91c, 103c
Gelatin duplicator ............................................................
Generator, electrical .........................................................
Glue-reversal (table XIV) .....................................................
Gradient tints ................................................................
Grainer, plate.................................................................
Graining ......................................................................
Chemical ............................. '..................................
Difficulties. (See table XI.)
Machine ...................................................................
Procedure .................................................................
Gumming, plates ...............................................................
Gum-reversal (table XV) .......................................................
.106
,117a
.66, 85, 88, 89
.62
.70
.69-73
.72
.70
.71
,6c, 79m, 83, 874, 119c
.66, 86, 89
Halftone screen ..........................................................,35O
Contact ..............................................................36, 54, 55<7
Distance. (See table III.)
Theory ................................................................355
Use ..................................................................35
Humidity, relative (table XXII) .........................................44a, 90c, 91/
Hygrometer ...............................................................79b
Page
43
55
55
47, 26, 28, 35, 48, 49
61
64
59
18, 61
20
20
20
91
37, 138
61
3, 76, 80
38, 78
55
89
100
5, 21, 32, 36, 50
43, 48, 49, 55
88, 98
90, 91, 112
121
138
64, 78, 81
61
67
67
69
67
69
4, 76, 78, 80, 139
64, 79, 81
32
36, 52, 54
32
32
39, 90, 92
Inks:
Adjustment .................................................................100, 103 106, 112
Developing .................................................................,6a, 79, 805 3, 74, 77
Distribution ...............................................................90c, 103 90, 112
Dr>ers .....................................................................914 91
Properties .................................................................91b 91
Vehicles ...................................................................91c 91
Intensifier, negative ...........................................................56b 56
Job analysis ..................................................................15 14
Job forms .....................................................................13 10>
158
Paragraphs Page
Layer tints .................................................................62 61
Lay-outs ....................................................................63-68 63
Color register ..........................................................67a 65
Combination .............................................................39b, 63, 65, 67b 59, 63, 65
Preparation..............................................................64 63
Step-and-repeat .........................................................63, '65, 67b 63, 65
Lens ........................................................................33 25
Care .....................................................................33d 31
Diaphragm control .......................................................33b, c, 35c 26, 28, 35
Lithography .................................................................5, 7 2, 5
Make-ready, press ........................................................906 88
Manufacturers ............................................................App II 147
Map-reproduction methods (table XXIV) ......................................3 1
Maps:
Cartographic ..............................................................10a 9
Colors ....................................................................186 16
Destruction ...............................................................122 140
Distribution ..............................................................121 140
Photo .....................................................................10a 9
Sizes .....................................................................11, 27 9, 21
Types .....................................................................10 9
Masking:
Copy ...................................................................25, 316
Negatives .............................................................606, 63, 76c
Military grids ...............................................................61
Mixing, chemical ...........................................................43, 44c, 87c
Mobile map reproduction equipment .........................................114
Negatives ......................................................................4
Base .......................................................................44a
Characteristics (table V) ..................................................44, 58
Clearing...................................................................47&, 48&, 506, 56/
Combination ...............................................................39
Continuous-tone ............................................................46, 55c
Contrast ...................................................................44a
Corrections ................................................................57-62
Densities. (See table IV.) Desensitizers .............................................................51
Development ...............................................................47/, 48 g, h
Difficulties. (See table IX.)
Dot etching ................................................................62
Double exposure ...........................................................59a, d, 69a
Exposure (table VI) ........................................................47 81
Mounting ............................................................. gg
Oxidation ........................................................... 73 qp
Tint.................................................................. Z 103c "
92
96
112
140
90, 91, 112
124, 127
1 S
3
67
69
69
72
78, 81
70
79, 81
76
75
78, 81
79, 81
23, 77
98
69, 111
112
Plate processing:
Albumen process ............................................
Blue lines ............................_•....................
Carbon-paper tracings .................................................
Difficulties. (See table XIII.)
Preparation .............................................................
Solutions .................................................................
Task force ................................................
.6a, 77-80, 87, 1195
.29, 82, 87g
.81
.75a
.78
.113
3, 74, 80, 139
23, 77, 81
77
74
127
Proofs:
Brownprints ...............................................................g8a
Color ........................................................................
Natural color ................................................................
Multiple exposure .........................................................g8£
Prehardener, negative .........................................................5g^
Press, offset .................................................................7 gg
Task force ................................................................113
Press operation ............................................................. 92-105
Blanket, mounting .........................................................95
Cleaning .....................................................................
Delivery ......................................................................99
Difficulties. (See table XVII.) Feeder .................................................................... 98
Formulas .................................................................105
Fountains .................................................................97
Ink adjustment ............................................................igg
Lubrication ...............................................................94
Plate adjustments ........................................................1Q2
Plate mounting ............................................................gg
Rapid projection printer .......................................................
Records ........................................................................
Reflex process .................................................................
Registration ...................................................................
Reproduction methods, general ..................................................
66
65
66
66
55
5, 88
127
93
96
112
90, 106
100
113
100
121
96
111
98
127
10
124
21, 37, 64, 75, 90
1
.112
.13
•111
.27, 37, 66-68, 79c, 90e
3
160
Paragraphs
Reversal process .............................................................Qb
Ruling ......................................................................61
3
61
Safelights ..................................................................42 38
Scheduling jobs .............................................................13 10
Scum ........................................................................102c 111
Specific gravity. {See table XXI.) Storage:
Maps .........................................................................120 140
Plates ....................................................................73d 70
Substitutes, albumen ............................................................,6a 3
Task force equipment ......................................................113
Temperature control: Equipment .................................................................44, 465, 118
Trays .................................................................39
Temperature conversion. {See table XX.) Thermometers ..............................................................43
Time estimates ............................................................14
Timers ....................................................................40
Tints:
Gradient ..............................................................18
Shading ...............................................................18
Tusching .................................................................805
Type faces ................................................................18a
127
39, 46, 138
38
39
12
38
16
16
77
16
Vacuum printing frame ............................................................76, 79/
Varnish, ink ....................................................................91c
73, 75
91
Walk-away ..............................................................
Washout ................................................................
Water supply ...........................................................
Weights and measures. {See table XIX.)
Wet-plate process ......................................................
Wetting agent ..........................................................
Whirler ................................................................
,75a
.77, 79h, 81c, 855
,114a, 116
.52
.35/,’ 44c, 47/, 48c, 765
6a, 75, 79c
72
74, 77, 78
137, 138
50
36, 45, 48, 74
3, 72, 74
★ U. S. GOVERNMENT PRINTING OFFICE: 1946—669124
161
7*3- K
UNT LIBRARIES DENTON TX 7S203
IIIIIIIIIIHIII
1001895236