Colorfastness to light

  

Colorfastness to light refers to a fabric's ability to resist fading when exposed to light.
To measure for Colorfastness to light, the fabric to be tested is exposed under specific conditions to a controlled light which simulates the sun's rays. At timed intervals, the test swatch is compared to a gray scale and the degree of fading is rated.
Class 5 = no fading
Class 1 = high degree of fading