ASTM C1649-14 (R2021) pdf free download.Standard Practice for Instrumental Transmittance Measurement of Color for Flat Glass, Coated and Uncoated.
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.
3. Summary of Practice
3.1 The color of transparent glass is measured in the total transmittance mode on a CIE—conforming diffuse instrument.
(See Guide E179 and Test Method E1348.) The glass color is expressed in CIE tristirnulus values based on spectral transmittance measurements over the full CIE spectral range of 350 to 78() nm with a maximum 10 nrn band pass. (See CIE 15:2004 and Practice E308.) For color measurement, use of a truncated spectral range of 400 to 700 nm is acceptable. (See CIE 15:2004.) Further information on the UV absorbing characteristics of the glass or glass coating, or both, may he determined by examining the spectral data in the 350 to 400 nrn range. If the instrument allows spectral measurement above 700 nm, useful information on the IR transmittance characteristics of the glass or glass coating may also be determined. If coatings are present, they are assumed to reflect and partially transmit light.
4. Significance and Use
4. 1 Color measurement quantifies the transmitted color ftr 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.
5. Apparatus
5.1 For color measurements, a CIE-conforming diffuse sphere instrument capable of making transmission measurements in the total transnhittance mode is required.
5.2 In addition, a device for mounting the glass sample flush at the transmission port is required.
5.3 The instrument and associated color quality software? tirmware shall be capable of converting measured spectral transmittance data to CIE L*, a* b*; Hunter L, a. b: or Y, x, v values calculated for CIE illuminant D65 and the CIE 1964 10 degree standard observer. (See Practice El 164.) Any of those mappings will serve as a full numerical color descriptor. (See Practice E308.) CIE Y transmittance can also serve as an over-all indicator of transmission. For other illurninantl observer combinations, see Practice E308 for guidance in use. For effective communication of color values between sites, color measurements must he expressed in the same color scale, illuminant, and standard observer.ASTM C1649 pdf download.