AATCC EP 7-2006 Instrumental Assessment of the Change in Color of a Test Specimen.
1.1 This evaluation procedure is inmethod of Evaluation Procedure 1, Gray Scale for Color Change (see 9.1), for as- sessing the change in color of a test spec- imen (see 9.2). It is applicable to any test method referring to Gray Scales except those which involve treatment with solutions containing fluorescent whitening agents (FWA).
2. Principle has been submitted to the colorfastness
2.1 The color of the specimen which test and the color of an identical untreated specimen are measured instrumentally. The CIELAB coordinates for lightness L*, chroma C* ab , and hue h ab are determined for both specimens as defined in CIE 15.2. The CIELAB differences ∆C* ∆L*, ab , and ∆H* ab are calculated and converted to a gray scale grade by means of a series of equations.
3. Terminology color of any kind whether in lightness,
3.1 color change, n.—a change in hue or chroma or any combination of these, discernible by comparing the test specimen with a corresponding untested specimen.
3.2 gray scale grade, n.— for color change, (GSc), the numerical value that is assigned to the change in color of a test specimen as compared to an original or untreated specimen.
4. Apparatus
4.1 Spectrophotometer or colorimeter meeting any one of the geometric definitions described in CIE publication 15.2, subclause 1.4 (see 9.3).
5. Test and Reference Specimens
5.1 Choose a representative sample of material, which has been subjected to a colorfastness test, of adequate size to fit the sample holder of the instrument used. Back this specimen with enough thicknesses of the original material to make the specimen opaque. (Opacity, or at least consistency, is required for accurate mea- surement.) Backing a single layer of the material with a white material that con- tains no FWAs is a permitted alternative provided both the reference specimen (original material) and test specimen are backed in an identical manner.
5.2 Form a layer of the reference specimen (original material) consisting of the same number of thicknesses as that pre- pared in 5.1.
6. Procedure specimen and calculate the CIELAB 6.1 Measure the color of the reference L*, C* ab , and h ab values using the data for the 10° observer and for illuminant D 9.4). 65 (see 6.2 Measure the color of the test specimen which has been subjected to the colorfastness test and make the same colorimetric calculations as done for the reference specimen. Then make the cal- culations as described below in Section 7.AATCC EP 7 pdf download.