The purpose of Color fastness to light test is to determine how much the color will fade when exposed to a known light source. It is an off line quality assurance system. Generally man wears the fabric and goes outside of the home for doing their job. In day; sun light fall on the fabric surface. So it needs to know how much protection ability have a fabric to sun light. It is determined by an experiment called color fastness to light. To measure the color fastness a blue scale is used. After completing the test, sample is compared with the blue scale.
Principle of Color Fastness to Light:
This test measures the resistance to fading of dyed textile when exposed to day light. The test sample is exposed to light for a certain time which is about 24 hours to 72 hours or by customer/buyer demand and compare the change with original unexposed sample the changes are assessed by Blue Scales.
Lightfastness testing is made using filtered xenon arc lamps which simulate UV and visible solar radiation more closely than any other artificial light source. They provide the best method for assessing the accelerated light ageing of products such as pigments, dyes and inks, which are sensitive to the long-wave and visible wavelengths of sunlight.
With appropriate filters fitted, direct sunlight, sunlight through window glass and in-store lighting conditions can be reproduced. A series of Blue Wool standards are included with every set of test samples to ensure that results are reliable and reproducible.