3. Equipment requirements
The lighting conditions of the light box should be sunny daylight (9:00-15:00), or an equivalent light source with an illuminance of 600lx or above. When rating, the discoloration gray sample card used must comply with GB/T 250-2008, and the staining gray sample card must comply with GB/T 251-2008. The color of the cover plate for the original sample and the sample after the test should be consistent, preferably neutral color or gray or black, and the size and shape should be roughly the same.
Visual rating is based on the gray sample card (discoloration gray card or staining gray card), which is divided into five levels and nine grades. Level one is the most serious fading, and level five is no fading. Next, the rating summary of various tests for color fastness is introduced. 

Yarn-dyed fabrics offer a wide range of color possibilities, as different colors of yarns can be combined to create complex designs.