ASTM C609-90(1995)

1.1 This test method covers the measurement of a visually small color difference between two pieces of solid-colored, glazed or unglazed ceramic tile, using any photoelectric instrument that meets the requirements specified in the test method. The amount and the direction of the color difference are expressed numerically, with sufficient accuracy for use in product specification.

1.2 This test method should not be used for determining small color differences between tile that have a multicolored, speckled, or textured surface, because the results may not be valid.

1.3 Color difference between specimens found to be metamers (see 3.2), by visual examination, can be accurately evaluated by spectrophotometric measurement only. Therefore, visual color comparison of test specimen and reference specimen should be made under incandescent light and under daylight fluorescent light before any instrumental measurement. If visual color difference under the two light sources is not of the same magnitude, the pair of tile must be considered metamers.

1.4 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.

1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.