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.