ASTM C1649-14(2021)

Standard Practice for Instrumental Transmittance Measurement of Color for Flat Glass, Coated and Uncoated

SIGNIFICANCE AND USE
4.1 Color measurement quantifies the transmitted color for glass. The user defines an acceptable range of color appropriate for the end use. A typical quality concern for transmittance color measurement of glass products is verification of lot-to-lot color consistency for end-user acceptance.  
4.2 If the transmitted color of a glass product is consistent from lot-to-lot and within agreed supplier-buyer acceptance criteria, the product’s color is expected to be consistent and acceptable for end-use.
SCOPE
1.1 This practice provides guidelines for the instrumental transmittance measurement of the color of coated and uncoated transparent glass. (See Terminology E284.)  
1.2 The practice specifically excludes fluorescent and iridescent samples.  
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-2021
• ICS: 17.180.20 - Colours and measurement of light
• ICS: 81.040.30 - Glass products
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.11 - Optical Properties

Relations

• Refers: ASTM E1164-23 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Nov-2023
• Refers: ASTM E308-17 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-May-2017
• Refers: ASTM E1348-15 - Standard Test Method for Transmittance and Color by Spectrophotometry Using Hemispherical Geometry
• Effective Date: 01-Nov-2015
• Refers: ASTM D2244-15a - Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
• Effective Date: 01-Aug-2015
• Refers: ASTM E308-15 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Apr-2015
• Refers: ASTM D2244-15e1 - Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
• Effective Date: 01-Jan-2015
• Refers: ASTM D2244-15 - Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
• Effective Date: 01-Jan-2015
• Refers: ASTM D2244-14 - Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
• Effective Date: 01-May-2014
• Refers: ASTM E284-13b - Standard Terminology of Appearance
• Effective Date: 01-Nov-2013
• Refers: ASTM E284-13a - Standard Terminology of Appearance
• Effective Date: 01-Jun-2013
• Refers: ASTM E284-13 - Standard Terminology of Appearance
• Effective Date: 01-Jan-2013
• Refers: ASTM E1164-12e1 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Jul-2012
• Refers: ASTM E1164-12 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Jul-2012
• Refers: ASTM E308-12 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Jul-2012
• Refers: ASTM E179-12 - Standard Guide for Selection of Geometric Conditions for Measurement of Reflection and Transmission Properties of Materials
• Effective Date: 01-Jul-2012

Overview

ASTM C1649-14(2021): Standard Practice for Instrumental Transmittance Measurement of Color for Flat Glass, Coated and Uncoated establishes guidelines for the instrumental measurement of transmitted color in transparent flat glass products, both coated and uncoated. Developed by ASTM International, this practice enables manufacturers, purchasers, and users to quantify and assess the color of glass using objective, replicable methods. Its focus ensures quality control, facilitates lot-to-lot color consistency, and supports supplier-customer agreement on color specifications in various industries, enhancing confidence in glass product performance for architectural, automotive, and other applications.

Key Topics

• Instrumental Transmittance Measurement: The standard details procedures for measuring color through glass using specialized CIE-conforming diffuse sphere instruments in total transmittance mode.
• Applicable Sample Types: Suitable for flat, transparent glass, including those with or without reflective coatings. It excludes fluorescent and iridescent samples.
• Measurement Parameters:
  • Uses CIE tristimulus values (L*, a*, b*, Hunter Lab, or Y, x, y) based on scanned spectral data, typically across the CIE spectral range of 350 to 780 nm.
  • Provides recommendations for color expression, illuminant (D65), and observer (10-degree standard) for reporting.
• Quality Assurance: Emphasizes the importance of verifying lot-to-lot color consistency within agreed supplier-buyer ranges for performance and end-use acceptance.
• Instrument Calibration: Advises regular calibration and verification of instruments using standard reference materials for reliable color assessment.
• Reporting: Specifies detailed documentation of sample identification, color scale, measurement conditions, and calculated color differences.

Applications

The ASTM C1649-14(2021) standard is highly practical for a variety of sectors where color uniformity and performance of glass are critical:

• Architectural Glass: Ensures floor-to-ceiling windows, facades, and curtain walls maintain consistent transmitted color, contributing to aesthetic and optical quality in buildings.
• Automotive Glass: Facilitates verification of windshield, side, and rear windows for color matching and compliance with safety standards.
• Container and Specialty Glass: Supports quality control in bottling and specialty glass products, enabling reliable supplier-buyer communication and acceptance.
• Quality Control in Manufacturing: Central to visual consistency and branding by providing measurable color standards throughout production batches.
• Supplier-Buyer Agreements: Assists in establishing objective, measurable color acceptance ranges to prevent disputes and enhance customer confidence.

Related Standards

The following standards are frequently referenced alongside ASTM C1649-14(2021) to provide comprehensive guidance on glass color measurement and transmittance properties:

• ASTM E1164: Practice for Obtaining Spectrometric Data for Object-Color Evaluation.
• ASTM E1348: Test Method for Transmittance and Color by Spectrophotometry Using Hemispherical Geometry.
• ASTM D2244: Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates.
• ASTM E308: Practice for Computing the Colors of Objects by Using the CIE System.
• ASTM E179: Guide for Selection of Geometric Conditions for Measurement of Reflection and Transmission Properties.
• ASTM E284: Terminology of Appearance.
• CIE 15:2004: Colorimetry standard from the International Commission on Illumination (CIE).

Conclusion

By following ASTM C1649-14(2021), organizations benefit from a robust, standardized method for quantifying glass color transmittance, promoting consistency in product appearance, enhancing transparency in quality assurance, and supporting global trade in glass products. Keywords: glass color measurement, transmittance, flat glass, coated glass, instrumental color analysis, ASTM C1649, quality control, color consistency, spectrophotometry, architectural glass standards.

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: C1649 − 14 (Reapproved 2021)
Standard Practice for
Instrumental Transmittance Measurement of Color for Flat
Glass, Coated and Uncoated
This standard is issued under the fixed designation C1649; 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. Scope E1164 PracticeforObtainingSpectrometricDataforObject-
Color Evaluation
1.1 This practice provides guidelines for the instrumental
E1348 Test Method for Transmittance and Color by Spec-
transmittancemeasurementofthecolorofcoatedanduncoated
trophotometry Using Hemispherical Geometry
transparent glass. (See Terminology E284.)
2.2 CIE Standard:
1.2 The practice specifically excludes fluorescent and iri-
CIE 15:2004 Colorimetry
descent samples.
1.3 The values stated in SI units are to be regarded as the
3. Summary of Practice
standard. The values given in parentheses are for information
only.
3.1 The color of transparent glass is measured in the total
transmittance mode on a CIE-conforming diffuse instrument.
1.4 This standard does not purport to address all of the
(See Guide E179 and Test Method E1348.) The glass color is
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- expressed in CIE tristimulus values based on spectral transmit-
tance measurements over the full CIE spectral range of 350 to
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. 780 nm with a maximum 10 nm band pass. (See CIE 15:2004
1.5 This international standard was developed in accor- and Practice E308.) For color measurement, use of a truncated
dance with internationally recognized principles on standard-
spectral range of 400 to 700 nm is acceptable. (See CIE
ization established in the Decision on Principles for the
15:2004.) Further information on the UV absorbing character-
Development of International Standards, Guides and Recom-
istics of the glass or glass coating, or both, may be determined
mendations issued by the World Trade Organization Technical
by examining the spectral data in the 350 to 400 nm range. If
Barriers to Trade (TBT) Committee.
the instrument allows spectral measurement above 700 nm,
useful information on the IR transmittance characteristics of
2. Referenced Documents
the glass or glass coating may also be determined. If coatings
2.1 ASTM Standards:
are present, they are assumed to reflect and partially transmit
D2244 Practice for Calculation of Color Tolerances and
light.
Color Differences from Instrumentally Measured Color
Coordinates
4. Significance and Use
E179 Guide for Selection of Geometric Conditions for
4.1 Color measurement quantifies the transmitted color for
Measurement of Reflection and Transmission Properties
glass.Theuserdefinesanacceptablerangeofcolorappropriate
of Materials
for the end use. A typical quality concern for transmittance
E284 Terminology of Appearance
color measurement of glass products is verification of lot-to-lot
E308 PracticeforComputingtheColorsofObjectsbyUsing
color consistency for end-user acceptance.
the CIE System
4.2 If the transmitted color of a glass product is consistent
This practice is under the jurisdiction of ASTM Committee C14 on Glass and
from lot-to-lot and within agreed supplier-buyer acceptance
Glass Products and is the direct responsibility of Subcommittee C14.11 on Optical
criteria, the product’s color is expected to be consistent and
Properties.
acceptable for end-use.
Current edition approved July 1, 2021. Published July 2021. Originally approved
in 2008. Last previous edition approved in 2014 as C1649 – 14. DOI: 10.1520/
C1649-14R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from U.S. National Committee of the CIE (International Commission
Standards volume information, refer to the standard’s Document Summary page on on Illumination), C/o Alan Laird Lewis, 282 E. Riding, Carlisle, MA 01741,
the ASTM website. http://www.cie-usnc.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1649 − 14 (2021)
5. Apparatus be taken to visually inspect the coated glass sample for any
significant visual abrasion and replace it if warranted.
5.1 For color measurements, a CIE-conforming diffuse
sphere instrument capable of making transmission measure-
9. Measurement Method
ments in the total transmittance mode is required.
9.1 Placetheglasssampleatthetransmittancemeasurement
5.2 Inaddition,adeviceformountingtheglasssampleflush
port.
at the transmission port is required.
9.2 At a minimum, scan the sample over the range of
5.3 The instrument and associated color quality software/
wavelengths required for measurement. Two scans with a 90º
firmware shall be capable of converting measured spectral
rotation of the samples are preferable. If practical and possible,
transmittance data to CIE L*, a* b*; Hunter L, a, b; or Y, x, y
scan at least one other area of the sample as well.
values calculated for CIE illuminant D65 and the CIE 1964 10
9.3 Correction for Reflection Loss of Uncoated Glass (Op-
degree standard observer. (See Practice E1164.) Any of those
tional):
mappings will serve as a full numerical color descriptor. (See
9.3.1 Because of histor
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