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 - provides clear guidelines for accurately measuring the color of transparent flat glass, including both coated and uncoated types, using instrumental methods. This practice is essential for establishing quantitative assessments of color in glass products to ensure consistency and compliance with end-user requirements. The standard targets quality assurance professionals, manufacturers, and suppliers involved in the production and selection of architectural, automotive, container, and specialty glass.

Key Topics

• Instrumental Color Measurement: Details procedures for performing transmittance color measurements using CIE-conforming diffuse sphere instruments, addressing best practices for sample handling and result communication.
• Applicable Glass Types: Covers transparent flat glass, both coated (partially reflective) and uncoated. Excludes fluorescent and iridescent samples.
• Color Data Expression: Describes the use of CIE tristimulus values, ensuring color is quantified and reported as CIE L*, a*, b*; Hunter L, a, b; or Y, x, y values under standard illuminant D65 and the CIE 1964 observer.
• Quality Control and Lot Consistency: Emphasizes the importance of verifying color consistency from lot-to-lot for meeting supplier and buyer acceptance criteria.
• Calibration and Equipment: Provides recommendations for instrument calibration, periodic verification using diagnostic standards, and proper setup to ensure reliable color measurements.
• Reporting Requirements: Specifies details for comprehensive reporting, including sample identification, test conditions, color systems used, and result units.

Applications

Implementing ASTM C1649-14(2021) supports a wide range of practical applications for industries relying on precise glass color control. Key uses include:

• Product Quality Assurance: Manufacturers use this standard to ensure each production lot of glass meets strict color tolerances, reducing the risk of rejection and maintaining brand reputation.
• Supplier-Buyer Agreements: The standard establishes a consistent basis for color acceptance between suppliers and buyers, promoting transparent, quantifiable criteria for delivered products.
• Architectural and Automotive Glazing: Ensures that glass panels installed in buildings or vehicles will match specified aesthetic and functional color requirements, contributing to uniformity in large-scale construction or fleet manufacturing.
• Container and Specialty Glass Production: Assists in monitoring and documenting color in bottles, laboratory ware, and customizable glass products to ensure compliance with regulatory and client expectations.
• Regulatory Compliance: Provides a globally recognized approach in line with World Trade Organization (WTO) principles, supporting international trade and minimizing technical barriers for glass products.

Related Standards

For comprehensive color measurement and control, the following ASTM and CIE standards are commonly referenced alongside ASTM C1649-14(2021):

• ASTM E284: Terminology of Appearance
• ASTM E308: Practice for Computing the Colors of Objects by Using the CIE System
• ASTM D2244: Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
• ASTM E1164: Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• ASTM E1348: Test Method for Transmittance and Color by Spectrophotometry Using Hemispherical Geometry
• CIE 15:2004: Colorimetry

By utilizing ASTM C1649-14(2021) and related standards, organizations enhance quality, streamline compliance, and facilitate effective communication throughout the glass supply chain. Implementing these guidelines ensures accurate transmittance color measurement for flat glass, supporting consistent product performance and international market access.

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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