ASTM C1901-21e1

Standard Test Method for Measuring Optical Retardation in Flat Architectural Glass

SIGNIFICANCE AND USE
5.1 Stress may be applied intentionally through a heat treatment or tempering process to increase mechanical strength and improve safety characteristics of glass sheets. The process itself makes it practically impossible to achieve a homogenous residual stress profile over a full glass panel. These variations are due to variations in type of glass (clear, tinted, coated, etc.), the fabrication, sheet geometry, heating, quenching, and cooling. Even though the level of inhomogeneity may not interfere with the global mechanical property of the glass sample, it can produce optical patterns called anisotropy (often commonly referred to as leopard spots). Today to evaluate this stress homogeneity people may use the subjective, non-standardized method of viewing through a polarized filter or employing a polariscope. The present test method provides guidelines for measuring a physical parameter, the optical retardation, directly linked to the local residual stress, at many locations on each heat-treated glass sheet.  
5.2 Through this test method one can obtain in a non-destructive manner, on-line to the tempering furnace equipment, a map of the retardation value of all glasses. That information can then be used:  
5.2.1 By the tempering operator to adjust the settings of the heat treatment process to optimize/tune both the levels optical retardations and its homogeneity on heat treated glass sheets.  
5.2.2 To provide a standardized way to measure optical retardation values for each glass panel that can be archived and communicated when desired.  
5.2.3 By customers and other stakeholders to develop/write specifications for the optical retardation values (not the visibility of the pattern) that are independently verifiable.  
5.3 This test method can also be used off-line to evaluate the optical retardation level and homogeneity of any heat-treated glass, for quality assurance or other purposes.
SCOPE
1.1 This test method addresses the measurement of optical anisotropy in architectural glass.  
1.2 This test method is a test method for measuring optical retardation. It is not an architectural glazing specification.  
1.3 The optical retardation values may be used to calculate/predict the amount of visible pattern, commonly known as anisotropy or iridescence, present in heat-treated glass.  
1.4 This test method applies to monolithic heat-treated (heat-strengthened and fully tempered) clear, tinted and coated glass.  
1.5 This test method does not apply to:  
1.5.1 Glass that diffuse light (that is, patterned glass, sand blasted glass, acid etched, etc.), or  
1.5.2 Glass that is not optically transparent (that is, mirrors, enameled or fritted glass).  
1.6 The optical measurement is integrated through the glass thickness, and therefore cannot be used to assess the level of tempering. It does not give information on the surface stress or center tension.  
1.7 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.8 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.  
1.9 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: Historical
• Publication Date: 31-Dec-2020
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.08 - Flat Glass

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: C1901 − 21
Standard Test Method for
1
Measuring Optical Retardation in Flat Architectural Glass
This standard is issued under the fixed designation C1901; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—Font of examples in Appendix X4 was changed, a duplicate subsection in Appendix X4 was removed, and edi-
torial changes to grammar were made throughout in February 2021.
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This test method addresses the measurement of optical
anisotropy in architectural glass.
2. Referenced Documents
1.2 This test method is a test method for measuring optical
2.1 Referencetothesedocumentsshallbethelatestrevision
retardation. It is not an architectural glazing specification.
unless otherwise specified by the authority applying this test
1.3 The optical retardation values may be used to calculate/
method.
predict the amount of visible pattern, commonly known as
2
2.2 ASTM Standards for Glass:
anisotropy or iridescence, present in heat-treated glass.
C162Terminology of Glass and Glass Products
1.4 This test method applies to monolithic heat-treated
C1036Specification for Flat Glass
(heat-strengthened and fully tempered) clear, tinted and coated
C1048Specification for Heat-Strengthened and Fully Tem-
glass.
pered Flat Glass
1.5 This test method does not apply to:
2.3 ASTM Standards for Optical Stress and Retardation
2
1.5.1 Glass that diffuse light (that is, patterned glass, sand Measurements:
blasted glass, acid etched, etc.), or C1279Test Method for Non-Destructive Photoelastic Mea-
surement of Edge and Surface Stresses in Annealed,
1.5.2 Glass that is not optically transparent (that is, mirrors,
enameled or fritted glass). Heat-Strengthened, and Fully Tempered Flat Glass
D4093Test Method for Photoelastic Measurements of Bire-
1.6 The optical measurement is integrated through the glass
fringence and Residual Strains in Transparent or Translu-
thickness, and therefore cannot be used to assess the level of
cent Plastic Materials
tempering. It does not give information on the surface stress or
center tension.
3. Terminology
1.7 The values stated in SI units are to be regarded as
3.1 Definitions:
standard. The values given in parentheses after SI units are
3.1.1 For definitions of terms used in this test method, refer
provided for information only and are not considered standard.
to Specifications C1036, C1048, and Terminology C162,as
1.8 This standard does not purport to address all of the
appropriate.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 analyzer, n—a polarizing element, typically rotatable
priate safety, health, and environmental practices and deter-
and positioned between the specimen being evaluated and the
mine the applicability of regulatory limitations prior to use.
observer.
1.9 This international standard was developed in accor-
3.2.2 anisotropy, n—property of being directionally depen-
dance with internationally recognized principles on standard-
dentwherebymeasurementstakenalongdifferentaxesproduce
ization established in the Decision on Principles for the
differences in a material’s physical or mechanical properties
Development of International Standards, Guides and Recom-
(absorbance, refractive index, conductivity, etc.).
1
This test method is under the jurisdiction of ASTM Committee C14 on Glass
2
and Glass Products and is the direct responsibility of Subcommittee C14.08 on Flat For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Glass. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved Jan. 1, 2021. Published February 2021. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
C1901-21E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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C1901 − 21
3.2.3 Babinet-Soleil compensator, n—an optical compensa- the fabrication, sheet geometry, heating, quenching, and cool-
tor that can be used to measure phase shifts locally in a ing. Even though the level of inhomogeneity may not interfere
polariscope or polarimeter using shifting quartz wedges. with the global mechanical property of the glass sample, it can
produce optical patterns called anisotropy (often commonly
3.2.4 birefringence, n—the optical p
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: C1901 − 21 C1901 − 21
Standard Test Method for
1
Measuring Optical Retardation in Flat Architectural Glass
This standard is issued under the fixed designation C1901; 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.
1
ε NOTE—Font of examples in Appendix X4 was changed, a duplicate subsection in Appendix X4 was removed, and edi-
torial changes to grammar were made throughout in February 2021.
1. Scope
1.1 This test method addresses the measurement of optical anisotropy in architectural glass.
1.2 This test method is a test method for measuring optical retardation. It is not an architectural glazing specification.
1.3 The optical retardation values may be used to calculate/predict the amount of visible pattern, commonly known as anisotropy
or iridescence, present in heat-treated glass.
1.4 This test method applies to monolithic heat-treated (heat-strengthened and fully tempered) clear, tinted and coated glass.
1.5 This test method does not apply to:
1.5.1 Glass that diffuse light (that is, patterned glass, sand blasted glass, acid etched, etc.), or
1.5.2 Glass that is not optically transparent (that is, mirrors, enameled or fritted glass).
1.6 The optical measurement is integrated through the glass thickness, and therefore cannot be used to assess the level of
tempering. It does not give information on the surface stress or center tension.
1.7 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.8 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.
1.9 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.
2. Referenced Documents
2.1 Reference to these documents shall be the latest revision unless otherwise specified by the authority applying this test method.
1
This test method is under the jurisdiction of ASTM Committee C14 on Glass and Glass Products and is the direct responsibility of Subcommittee C14.08 on Flat Glass.
Current edition approved Jan. 1, 2021. Published February 2021. DOI: 10.1520/C1901-21.10.1520/C1901-21E01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
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C1901 − 21
2
2.2 ASTM Standards for Glass:
C162 Terminology of Glass and Glass Products
C1036 Specification for Flat Glass
C1048 Specification for Heat-Strengthened and Fully Tempered Flat Glass
2
2.3 ASTM Standards for Optical Stress and Retardation Measurements:
C1279 Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-
Strengthened, and Fully Tempered Flat Glass
D4093 Test Method for Photoelastic Measurements of Birefringence and Residual Strains in Transparent or Translucent Plastic
Materials
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Specifications C1036, C1048, and Terminology C162, as
appropriate.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 analyzer, n—a polarizing element, typically rotatable and positioned between the specimen being evaluated and the
viewer.observer.
3.2.2 anisotropy, n—property of being directionally dependent whereby measurements taken along different axes produce
differences in a material’s physical or mechanical properties (absorbance, refractive index, conductivity, etc.).
3.2.3 Babinet-Soleil compensator, n—an optical compensator that can be used to measure phase shifts locally in a polariscope or
polarimeter using shifting quartz wedges.
3.2.4 birefringence, n—the optical property of a material having a refractive index that depends on the polarization and
propagation direction of light.
3.2.5 compensation methods, n—(1) Sénarmont compensator uses l
...