[Federal Register Volume 59, Number 55 (Tuesday, March 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-6638]


[[Page Unknown]]

[Federal Register: March 22, 1994]


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DEPARTMENT OF THE TREASURY

Customs Service
[T.D. (94-25)]

 

Testing of Pressed and Toughened (Specially Tempered) Glassware

AGENCY: Customs Service, Department of the Treasury.

ACTION: Final notice on the testing of pressed and toughened (specially 
tempered) glassware.

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SUMMARY: Customs has completed a review of the comments submitted by 
interested parties on the testing of certain articles of glass to 
ascertain if they have been ``pressed and toughened (specially 
tempered).'' These articles are normally imported under Subheading 
numbers 7013.29.05, 7013.32.10, 7013.39.10, and 7013.99.20 of the 
Harmonized Tariff Schedule of the United States (HTSUS).

FOR FURTHER INFORMATION CONTACT: Mr. Robert L. Zimmerman, Jr., Office 
of Laboratories & Scientific Services, (202) 927-1060.

SUPPLEMENTARY INFORMATION:

Background

    The U.S. Customs Service published the last in a series of requests 
for comments on a proposed method for the testing of ``pressed and 
toughened (specially tempered)'' glassware in the Federal Register 
(Vol. 58, No. 192, October 6, 1993). Specifically, comments were 
requested on a part of the proposed method entitled ``Cutting Test for 
Opaque Glassware''. These glassware articles are normally imported 
under Subheading numbers 7013.29.05, 7013.32.10, 7013.39.10, and 
7013.99.20 of the Harmonized Tariff Schedule of the United States 
(HTSUS). Articles of ``safety glass, consisting of toughened (tempered) 
* * * glass'' normally imported under Heading 7007 of the HTSUS, e.g., 
architectural plate glass, vehicle windshields, were not within the 
purview of the notice.
    The U.S. Customs Service received responses from two interested 
parties as a result of the October 6, 1993, Notice. Both respondents 
endorsed the incorporation of the cutting test into the overall method.
    Issue 1--Fluorosilicate glass. Respondent A offered a caution on 
the behavior of fluorosilicate glass articles when subjected to the 
cutting test. According to their comments, ``while soda lime tempered 
glass and borosilicate tempered glass does indeed break almost 
immediately upon contact with the saw, fluorosilicate glass will not 
break until the saw has passed through at least a part of the glass.'' 
Customs has studied this point and has found that the respondent's 
comments are valid. This study has also shown that, while a deeper cut 
into the glass article is necessary, the article will not sever 
``cleanly'' into two pieces as does annealed glass. Therefore, 
appropriate changes have been made to the method to address the 
fluorosilicate issue.
    Issue 2--Thermal Shock Conditions. Respondent B included a comment 
on thermal shock conditions. These issues have been discussed in 
previous Federal Register Notices on this subject. Customs has no 
further comments on this topic at this time.

Conclusion

    Effective as of the date of publication of this Notice in the 
Federal Register, Customs will conduct the analysis of all glassware 
falling under the purview of the aforementioned HTSUS item numbers, 
using the following method.

METHOD

    Safety Precaution: Certain procedures described in this method pose 
a potential hazard to personnel from the proximity to or handling of 
breaking or broken glass. This method shall not be undertaken without 
supervisory concurrence that adequate precautions for personal safety 
have been implemented.

I. Apparatus

A. Photographic Equipment

    A camera (equipped with flash or supplemented by adequate lighting) 
is recommended for making a permanent record of unusual samples and 
test results.

B. Polariscope

    The basic instrument consists of a light source, a polarizer, and 
an analyzer. The addition of a full-wave retardation, or tint, plate 
permits observation of color-enhanced stress patterns. Ideally, the 
working space, or distance between the polarizer and the analyzer, 
should be large enough to accommodate samples ranging up to eight 
inches in height.

C. Tile Saw (or Similar Table-Mounted Circular Saw)

    A tile saw having a cutting head which can be adjusted horizontally 
and vertically and which is equipped with an 8 to 12 inch diameter 
continuous rim diamond blade designed for wet cutting glass is adequate 
for testing opaque glassware articles.

D. Other Apparatus and Supplies

    The method requires various common laboratory articles such as a 
caliper or similar device for measuring the diameter of the opening and 
the maximum inside diameter of the sample, an oven and water bath, and 
other equipment and supplies. Appropriate safety devices and personal 
protective equipment are also required.

II. Preparation of the Sample

    When available a representative number of samples should be 
analyzed. However, it is recognized that for any of several reasons, 
e.g., cost of the item, only a limited number of samples may be 
submitted for analysis. The possibility exists that only one sample may 
be available for testing.

III. Analysis Procedures

    The following procedures may be conducted in whatever order the 
analyst deems is appropriate for the particular sample being examined. 
The test protocol should be terminated at the point that a sample fails 
to meet any of the key criteria, i.e., ``pressed'', ``toughened'', 
``tempered'', or ``specially''.

A. Macroscopic Analysis

    Examine each article of glassware as follows:
    1. Visual Inspection:
    Inspect the sample for the following:
     Identifying marks, labels, sizes, etc., especially those 
that may have been caused by a push-up valve and a mold that have been 
pressed into the article;
     The style (stemware, tumbler, bowl, plate, etc.);
     The presence of ribs, handles, flutes, etc.;
     The size of the rim or opening, if applicable;
     The size of the most bulbous portion of the article;
     Any other unusual characteristics (e.g., chips, cracks)
    Interpretation of Visual Inspection results: Characteristics such 
as mold marks, ribs, handles, and flutes are often indicative of a 
pressed rather than blown glass article.
    2. Dimensional Measurement (applies only to stemware, tumblers, 
bowls, etc.):
     Using a caliper or similar device, measure the minimum 
diameter of the mouth, opening, or upper rim of the sample. With the 
same device, measure the maximum inside diameter. Record both 
measurements.
    Interpretation of Dimensional Measurement results: A sample having 
a maximum inside diameter greater than the minimum diameter of the 
mouth, opening, or upper rim is not likely to have been ``pressed''.
    Interpretation of the Macroscopic Analysis Test: The analyst is 
advised to consider the overall features of the article and the 
dimensional analysis test results in determining that an article has 
been ``pressed''. If the results show that the sample is not 
``pressed'' the testing sequence for this sample should be terminated 
at this point.

B. Thermal Shock Test

     Heat the sample(s) in an oven to 160  deg.C for 30 
minutes.
     Remove 1 sample from the oven and immediately immerse it 
in a water bath set at 25  deg.C. This effects a 135  deg.C difference 
in temperature.

    Note: Reasonable alternate oven and water bath settings up to 
 10  deg.C acceptable as long as the 135  deg.C 
difference in temperature is maintained.

    Interpretation of Thermal Shock Test results: Annealed glassware 
and inadequately or partially tempered glassware will generally not 
survive this test of durability or toughness. If breakage occurs, the 
sample is not ``toughened'' for Customs purposes. Record the findings, 
and terminate the analysis.

C. Evaluation of Temper

1. Polariscopic Examination
    This method for the qualitative evaluation of temper in glassware 
should be conducted only on transparent or translucent articles. This 
method is not applicable to opaque items or to articles which have been 
tempered by a process other than thermal tempering. In addition, some 
translucent articles will not transmit enough polarized light to permit 
the observation of stress patterns; these items should be evaluated for 
temper using the Cutting Test.
     Place the full-wave retardation plate (tint plate) between 
the polarizer and the analyzer. The polarized light must pass through 
both the sample and the retardation plate for the color-enhanced 
polariscopic pattern to be observed through the analyzer. Position the 
retardation plate in direct contact with the polarizer or, 
alternatively, just in front of the analyzer.
     Turn on the light source.
     Evaluate the stress in the bottom of the intact article by 
placing its bottom surface in contact with the polarizer so that the 
polarized light passes perpendicularly through the bottom surface, or 
as close to perpendicularly as possible, depending upon the article's 
shape. [This positioning does not work well with stemware because of 
color patterns caused by the stem itself. With these items, it will be 
necessary to hold the glass at a slight angle to view the base and the 
bowl separately.]
     Evaluate the stress in the sides of the intact article, 
especially near the rim or edge, by positioning the article so that the 
polarized light passes perpendicularly through the sides near the rim, 
or as close to perpendicularly as possible, depending upon the 
article's shape. Observation of the stress patterns in the sidewall and 
rim areas should be made while viewing through a single thickness of 
glass. For some items, especially stemware, tumblers, and mugs, this 
will require holding the article at a slight angle to the polarizer 
(open end raised slightly).
    Interpretation of the Polariscopic Examination: Thermal tempering 
of glassware involves heating to the softening point followed by rapid 
cooling. The surfaces cool first and reach a temperature where they 
become rigid. With further cooling, the interior or core tries to 
shrink but is prevented from doing so by the rigid surface layers. This 
results in the surfaces being locked into a state of high compression 
and the interior locked into compensating tension.
    When polarized light rays travel through a stressed material, they 
divide into slow and fast fronts. As a result of the difference in 
speed of the slow and fast rays, interferences occur and a pattern of 
colors is observed. These colors can be used to evaluate the stresses 
in the article. As the stress increases, the observed color changes to 
reflect the amount of stress. The color changes follow a rigorous 
sequence as the stress-induced retardation, or distance between the 
fast and slow rays, increases. In low-stress areas, black and shades of 
gray are seen. Evaluation of low stress is simplified by using a color-
enhancing retardation or tint plate which adds a shift of one fringe 
order, or 565 nm, in the color pattern throughout the observed field. 
With the tint plate in place, even low and moderately stressed areas 
will exhibit a contrasting color effect.
    Annealed glassware will exhibit a uniform coloration of the 
polarized light passing through it; there will be essentially no change 
from background. Tempered articles will exhibit non-uniform coloration 
of the polarized light on the bottom surface and sidewalls and bands of 
color parallel to the rim or lip. [Note: With highly colored articles, 
it may be helpful to conduct the polariscopic exam without the tint 
plate. There will be no color enhancement, but the gray to black 
interference patterns should be readily discernible in tempered 
articles.]
    If the sample passes the Thermal Shock Test and shows evidence of 
full-surface tempering (as opposed to rim-tempering or partial 
tempering) when examined polariscopically, the sample has been 
``toughened (specially tempered)'' for Customs purposes.
2. Cutting Test for Opaque Glassware
    This test is applicable to opaque articles and to those translucent 
articles which can not be examined polariscopically because of 
inadequate transmission of the polarized light.
     Ensure that the saw is equipped with a continuous rim 
diamond blade designed for wet cutting glass.
     Adjust the cutting head of the saw vertically and 
horizontally, as necessary, to accommodate the glassware article.
     Be sure the water supply to both sides of the diamond-
rimmed blade is adequate.
     Turn on the saw.
     While holding or otherwise securing the article to prevent 
twisting and binding during the cutting, slowly and gently move the 
article into contact with the blade.
     Proceed with the cutting.
    Interpretation of the Cutting Test: Annealed (non-tempered) 
glassware will readily accept the diamond-rimmed blade and will be 
cleanly cut in half. Tempered glass, on the other hand, will break into 
pieces when cut. Tempered soda lime and borosilicate glass will break 
almost immediately, whereas tempered fluorosilicate glass will not 
break until the blade has cut through at least part of the article. The 
extent of cutting needed to induce breakage may vary from item to item, 
but in no event will tempered articles be cleanly cut in half by the 
diamond-rimmed blade.
    A sample that passes the Thermal Shock Test and shows evidence of 
tempering per the guidance given above for the Cutting Test has been 
``toughened (specially tempered)'' for Customs purposes.

    Dated: March 15, 1994.
George D. Heavey,
Director, Office of Laboratories and Scientific Services.
[FR Doc. 94-6638 Filed 3-21-94; 8:45 am]
BILLING CODE 4820-02-P