ASTM C1649:14(R2021) pdf free download – Standard Practice for Instrumental Transmittance Measurement of Color for Flat Glass, Coated and Uncoated.
5. Apparatus
5.1 For color measurements, a CIE-conforming diffuse sphere instrument capable of making transmission measurements in the wtal transmittance 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/ firmware shall be capable of converting measured spectral transmittance data to CIE L, a b4 Hunter I., a. b; or Y. x, y values calculated for CIE illuminant D65 and the CIE 1%-I 10 degree standard observer. (See Practice E1164.) Any of those mappings will serve as a full numerical color descriptor. (See Practice E3OK.) CIE Y transmittance can also serve as an over-all indicator of transmission. For other illuminani/ observer combinations, see Practice E308 for guidance in use. For effective communication of color values between sites. color measurements must be expressed in the same color scale, illuniinant. and standard observer.
5.4 The expression of a color difference in terms of rectangular. polar, or elliptical color differences shall serve to quantify the difference between target product color and lot color (See Practice 1)2244.)
6. Materials
6.1 Samples are uncoatcii or partially reflective coated transparent glass with defined substrate, coating compositions. and thicknesses.
7. Hazards
7.1 Consult Material Safety Data Sheets, and local regulations for all materials used in this practice.
8. Color Instrument Calibration and Set up Procedure
8.1 Prepare instrument for operation by following the instrument manufacturer’s instructions.
8.2 Use instrument standardization to set the color instrument to the assigned values for the transmission standards supplied by the manufacturer or other suitable reference naterial.
8.3 To verify consistency over time in the performance of the color instrument, read and record color values of an instrument diagnostic standard (such as a color standard or didymium lifter) at regular intervals. Care should be taken to visually inspect these standards for any significant visual abrasion and replace it if warranted.
8.4 As the stability characteristics of coated and un-coated glass are generally good. the user may. at their option, read aNorE 2- Sample presentation includes any side or positional informa-
tion; the area of view measured in each reading; the number of readings
averaged and if readings were taken in a speceife pattem.
10.1.5 The CIE Y value may also be reported to nearest hundredths of a unit, as an instrumental measurement of the
overall transmittance of the transparent glass.
11. Keywords
11.1 coatings; color; glass; transmitancend record color values for a coated glass sample to document consistency in the measurement method over time.