[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
