Color Fastness
Color fastness, also known as dyeing fastness or dyeing resistance, refers to a textile's ability to resist color changes during processing and use.
The fastness grade is determined by evaluating the discoloration of the test sample and the dye transfer onto an uncolored backing fabric. Color fastness testing is a routine quality assessment for textiles.
During use, textiles are subjected to external factors such as light exposure, washing, ironing, perspiration, friction, and chemical agents. Some dyed textiles also undergo specialized finishing processes like resin treatment, flame retardant finishing, sand washing, or napping. This necessitates that the color of dyed textiles maintain a certain level of fastness.
Color fastness ratings are assigned as follows: all categories except lightfastness (R grade) are rated on a 5-point scale. Higher grades indicate superior colorfastness. Leather testing methods include color fading (changes in the leather's own color) and color transfer (staining of contact materials).
The colorfastness to fading test involves treating a leather sample under specified conditions and then grading the color difference between that sample and an untreated control sample against a standard gray scale. The colorfastness to staining test involves placing the sample in contact with a standard white cloth under specified conditions. The degree of color transfer and staining on the white cloth is then measured and graded using a gray scale for staining.
Staining fastness
Garments composed of different colored sections may experience dye migration from one area to another during storage, typically from darker to lighter sections. This phenomenon differs from sublimation as it occurs below sublimation temperatures and affects non-sublimation dyes as well. It is primarily observed in synthetic fabrics like polyester, though other materials may also exhibit migration.
Color transfer primarily results from two causes: First, dye migration occurs, particularly the free dye released from dispersed or reactive dyes through floating or migration within the fiber. This free dye may then dye fibers on the surface of another sample, especially dark colors dyeing light colors, leaving behind granular or imprint-like stains on the other sample's surface. Second, fibers shed due to friction, transferring from one sample to another.
