Standard Test Method for Color and Color Difference of Whitewares by Abriged Spectrophotometry

Abstract

5.1 The most direct and accessible methods for obtaining the color coordinates of ceramic glazes and related whitewares are by instrumental measurement using spectrophotometers or colorimeters with either hemispherical or bidirectional optical measuring systems. This test method provides procedures for such measurement by reflectance spectrophotometry using a hemispherical optical measuring system. 5.2 This test method is especially suitable for measurement of the following types of specimens for the indicated uses (see Practice E805). 5.2.1 All types of ceramic glaze and related whiteware specimens to obtain data for use in computer colorant formulation. 5.2.2 Ceramic glaze and related whiteware specimens for color assessment. 5.2.2.1 For the measurement of plane-surface high-gloss specimens, the specular component should generally be excluded during the measurement. 5.2.2.2 For the measurement of plane-surface intermediate-gloss (satin) specimens, where the first-surface reflection component may be distributed over a wide range of angles, measurement may be made with the specular component included, but the resulting color coordinates may not correlate best with visual judgments of the color. Measurement with specular excluded may lead to better correlations. 5.2.2.3 For the measurement of plane-surface, low-gloss (matte) specimens, the specular component may either be excluded or included, as no significant difference in the results should be apparent. 5.3 An estimate of gloss may be obtained by measuring the reflection both with the specular component of reflection included and excluded, and then calculating the difference between the two measurements at several wavelengths across the visible spectrum, as described in 10.2.