GB/T 8424.2-2001 "Spinning & weaving products colour fastness test, instrumental evaluation method of relative whiteness" standard defines a quantitative method for the measurement of Spinning & weaving products whiteness and light shade index, including the test of Spinning & weaving products containing fluorescent whitening agent. The standard uses CIE tristimulus values and chromaticity coordinates to calculate whiteness and light shade index, which is used to evaluate the whiteness and color cast of Spinning & weaving products. Before testing, it is necessary to check whether the sample contains fluorescent whitening agent and use a suitable colorimeter for determination. The standard applies to industrial and commercial applications, and the results are only relative whiteness evaluations, not absolute whiteness measurements.