ASTM C148-17(2022)

Standard Test Methods for Polariscopic Examination of Glass Containers

SIGNIFICANCE AND USE
4.1 These two test methods are provided for evaluating the quality of annealing. These test methods can be used in the quality control of glass containers or other products made of similar glass compositions, where the degree of annealing must be verified to ensure quality products. These test methods apply to glass containers manufactured from commercial soda-lime-silica glass compositions.
SCOPE
1.1 These test methods describe the determination of relative optical retardation associated with the state of anneal of glass containers. Two alternative test methods are covered as follows:    
Sections  
Test Method A—Comparison with Reference Standards
Using a Polariscope  
6 – 9  
Test Method B—Determination with Polarimeter  
10 – 12  
1.2 Test Method A is useful in determining retardations less than 150 nm, while Test Method B is useful in determining retardations less than 565 nm.  
Note 1: The apparent temper number as determined by these test methods depends primarily on (1) the magnitude and distribution of the residual stress in the glass, (2) the thickness of the glass (optical path length at the point of grading), and (3) the composition of the glass. For all usual soda-lime silica bottle glass compositions, the effect of the composition is negligible. In an examination of the bottom of a container, the thickness of glass may be taken into account by use of the following formula, which defines a real temper number, TR, in terms of the apparent temper number, TA, and the bottom thickness, t:
This thickness should be measured at the location of the maximum apparent retardation. Interpretation of either real or apparent temper number requires practical experience with the particular ware being evaluated.  
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Jun-2022
• ICS: 81.040.30 - Glass products
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.07 - Glass Containers

Relations

• Refers: ASTM C162-23 - Standard Terminology of Glass and Glass Products
• Effective Date: 01-Oct-2023
• Refers: ASTM C1426-14(2020) - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 01-Aug-2020
• Refers: ASTM C224-78(2020) - Standard Practice for Sampling Glass Containers
• Effective Date: 01-Aug-2020
• Refers: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 01-Nov-2015
• Refers: ASTM C224-78(2014) - Standard Practice for Sampling Glass Containers
• Effective Date: 01-Oct-2014
• Refers: ASTM C1426-14 - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 01-May-2014
• Refers: ASTM C1426-09 - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 01-Nov-2009
• Refers: ASTM C224-78(2009) - Standard Practice for Sampling Glass Containers
• Effective Date: 01-May-2009
• Refers: ASTM C162-05(2010) - Standard Terminology of Glass and Glass Products
• Effective Date: 01-Oct-2005
• Refers: ASTM C162-05 - Standard Terminology of Glass and Glass Products
• Effective Date: 01-Oct-2005
• Refers: ASTM C1426-99(2004) - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 01-Oct-2004
• Refers: ASTM C162-04 - Standard Terminology of Glass and Glass Products
• Effective Date: 01-Jun-2004
• Refers: ASTM C224-78(2004)e1 - Standard Practice for Sampling Glass Containers
• Effective Date: 01-Apr-2004
• Refers: ASTM C162-03 - Standard Terminology of Glass and Glass Products
• Effective Date: 10-Jul-2003
• Refers: ASTM C1426-99 - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 10-May-1999

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C148 − 17 (Reapproved 2022)
Standard Test Methods for
Polariscopic Examination of Glass Containers
This standard is issued under the fixed designation C148; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods describe the determination of rela-
ization established in the Decision on Principles for the
tive optical retardation associated with the state of anneal of
Development of International Standards, Guides and Recom-
glass containers. Two alternative test methods are covered as
mendations issued by the World Trade Organization Technical
follows:
Barriers to Trade (TBT) Committee.
Sections
Test Method A—Comparison with Reference Standards 6–9
2. Referenced Documents
Using a Polariscope
Test Method B—Determination with Polarimeter 10–12
2.1 ASTM Standards:
1.2 Test MethodAis useful in determining retardations less
C162 Terminology of Glass and Glass Products
than 150 nm, while Test Method B is useful in determining
C224 Practice for Sampling Glass Containers
retardations less than 565 nm.
C1426 Practices for Verification and Calibration of Polarim-
eters
NOTE 1—The apparent temper number as determined by these test
methods depends primarily on (1) the magnitude and distribution of the
residual stress in the glass, (2) the thickness of the glass (optical path
3. Terminology
length at the point of grading), and (3) the composition of the glass. For
3.1 Definitions—For definitions of terms used in these test
all usual soda-lime silica bottle glass compositions, the effect of the
methods see Terminology C162.
composition is negligible. In an examination of the bottom of a container,
the thickness of glass may be taken into account by use of the following
formula, which defines a real temper number, T , in terms of the apparent
4. Significance and Use
R
temper number, T , and the bottom thickness, t:
A
4.1 These two test methods are provided for evaluating the
T 5 T 0.160 ⁄ t , where t is in inches, or
~ !
R A quality of annealing. These test methods can be used in the
quality control of glass containers or other products made of
T 5 T 4.06 ⁄ t , where t is in millimetres.
~ !
R A
similarglasscompositions,wherethedegreeofannealingmust
This thickness should be measured at the location of the maximum ap-
be verified to ensure quality products. These test methods
parent retardation. Interpretation of either real or apparent temper num-
apply to glass containers manufactured from commercial
ber requires practical experience with the particular ware being evalu-
soda-lime-silica glass compositions.
ated.
1.3 The values stated in SI units are to be regarded as the
5. Sampling
standard. The values given in parentheses are for information
5.1 Methods of sampling a minimum lot from a group of
only.
containers of a given type are given in Practice C224 for the
1.4 This standard does not purport to address all of the
various situations to which that method may apply.
safety concerns, if any, associated with its use. It is the
TEST METHOD A—COMPARISON WITH
responsibility of the user of this standard to establish appro-
REFERENCE STANDARDS USING A POLARISCOPE
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
6. Apparatus
6.1 Polariscope, conforming to the following requirements:
These test methods are under the jurisdiction of ASTM Committee C14 on
Glass and Glass Products and are the direct responsibility of Subcommittee C14.07
on Glass Containers. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2022. Published July 2022. Originally approved contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
in 1939. Last previous edition approved in 2017 as C148 – 17. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
C0148-17R22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C148 − 17 (2022)
6.1.1 The degree of polarization of the field at all points greater than that of N disks but less than N + 1 disks, the
shall not be less than 99 %. apparent temper grade is judged to be that of N + 1 disks. The
6.1.2 The field shall be a minimum of 51 mm (2 in.) in apparent temper number is always determined to be the next
diameter greater than the diameter of the container to be integral temper number greater in value than the actual
measured. The distance between the polarizing and analyzing observed value as seen in the following table:
elements shall be sufficient to allow the inside bottle bottom
Apparent Temper Number Observed Temper
surface to be viewed through the open container finish.
1 less than 1 disk
6.1.3 A sensitive tint plate, having a nominal optical retar-
2 less than 2, greater than 1 disk
dation of 565 nm, with a variation across the field of view of
3 less than 3, greater than 2 disks
4 less than 4, greater than 3 disks
less than 5 nm and with its slow axis at 45° to the plane of
5 less than 5, greater than 4 disks
polarization, shall be used. Such an orientation will produce a
6 less than 6, greater than 5 disks
A
magenta background in the field of view. The brightness of the
polarized field illuminating the sample shall be a minimum of
A
Evaluation by polarimeter (Test Method B) should be used for apparent temper
300 cd/m .
numbers greater than six.
NOTE 2—Color discrimination remains satisfactory with retardations
8.2 Examination of Square, Oval, and Irregular Shapes—
between 510 nm and 580 nm, but optimum conditions are attained at
Make the polariscopic examination of that container curve or
565 nm.
corner that shows the maximum order of retardation color and
6.1.4 Samples must be allowed to equilibrate until the entire
record the temper number in accordance with the procedure
thickness of glass is at room temperature.
outlined in 8.1.
7. Calibration and Standardization 8.3 Examination of the Container Sidewalls—Match the
maximum retardation color observed in the container sidewall
7.1 A set of not less than five standardized glass disks of
with the maximum retardation color at the calibration point of
known retardation stress shall be used to cover the range of
the standard reference disks, and record the apparent temper
commercial container annealing. Such disks shall be circular
number in accordance with the procedure outlined in 8.1.1.
plates of glass not less than 76 mm (3 in.) nor more than
102 mm (4 in.) in diameter. Each disk shall have a nominal 8.4 Examination of Colored Ware—Using the polariscope
retardation at the calibration point, 6.4 mm (0.25 in.) from the
with the tint plate in the field of view, rotate the container to
outer circumference of the disk, corresponding to not less than determine the location of the highest order retardation color at
21.8 nm nor more than 23.8 nm of optical retardation. Each
the inside knuckle position. View the bottom of the container
disk shall have a nominal retardation at the calibration point, through the open container finish and select as a reference area
6.4 mm (0.25 in.) from the PHYSICAL EDGE of the GLASS the darkest appearing area of the container bottom having
disk, corresponding to not less than 21.8 nm nor more than minimum retardation, usually found at the center of the
23.8nmofopticalretardation.Ifthediskismountedinaframe container bottom. Then, with the tint plate in position, hold a
that covers the glass edge, refer to the instructions provided by standard reference disk under the reference area in the bottom
the supplier of the strain disk set with regard to the distance to of the container such that the calibration point on the disk is
the calibration point from the frame ID. If unknown, the disks directly under the reference area in the center bottom of the
may be removed from the frame, the calibration point marked container. Compare the retardation color of the reference area
accordingly, and the disks placed back into their frames. in the container center bottom as modified by the standard
reference disk with the maximum retardation color as normally
8. Procedure
observed at the inside knuckle of the container bottom. If this
color is greater than the modified color of the reference area,
8.1 Examination of the Bottom of Cylindrical Flint
use two or more disks and grade the
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