What Tests are used to Measure Colorfastness to Light?
“Colorfastness to light refers to a fabric’s ability to resist fading when exposed to light.”

The test used to measure colorfastness to light is AATCC 16 option 1 or 3. “The AATCC 16 Option 1 and 3 are test methods of the American Association of Textile Chemists and Colorists (AATCC). ACT recognizes both methods where the only difference is the light source being used. In AATCC 16 Option 1 a Carbon-Arc lamp is used as the light source and in AATCC 16 Option 3 a Xenon-Arc lamp is used. Under both methods a strip of fabric (part of which is protected by a special paper card) is placed in a fadometer and exposed to 40 hours of accelerated fading units (AFU). After the exposure the difference in color between the exposed and protected parts of the fabric are compared to the AATCC gray scale and the degree of fading is rated.”

Grade 5 = no fading
Grade 4 = slight fading
Grade 1 = high degree of fading

SOURCE: Association of Contact Textiles Website