5.1 The gray scale grade GS_C is useful to evaluate the color difference of any pair of colors that have been subjected to a test whose severity of result is nominated by color difference of the treated member to the untreated member. This includes, but is not limited to, scrub tests, exterior exposures, crocking tests, blocking tests, certain abrasion tests, and color transfer tests.

5.2 A major advantage of the instrumental method of obtaining gray scale grades is that under the visual method substantial screening and training of the operators in visual color assessment is required. No such burden is placed on the operators in this instrumental method.

5.3 The method is usually not used for staining tests which have their own gray scale for staining.

1.1 Test Method D2616 describes a painted gray scale and the procedure to be used in the visual evaluation of color differences on non-self-luminous materials by comparison to this scale. This practice provides an alternative method of obtaining a similarly valued result by an instrumental method.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard, except that the test results of this test method are converted by the calculations to an arbitrary visual scale defined by Test Method D2616, whose units are called GS_C (Gray Scale for Change in Color).

1.3 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.