washfastness

Washfastness, or colorfastness to washing, is the ability of dyed or printed textiles to retain their color when subjected to laundering. It measures resistance to fading, changing hue, or color transfer to other fabrics or the washing medium.

It depends on fiber type, dye chemistry, chemical finishing, and fabric construction. Natural fibers often have different washfastness profiles than synthetics; reactive and vat dyes typically offer good washfastness on cotton, disperse dyes on polyester. Finishes such as crosslinking resins can improve washfastness but may affect hand or breathability. Water temperature, detergents, pH, mechanical action, and load conditions influence outcomes, as do water hardness and washing cycles.

Testing for washfastness uses standardized methods that expose fabric samples to defined laundering procedures, followed by evaluation of color changes or staining using a gray scale or instrumental colorimetry. Ratings range from no color change with no staining to severe change or staining. Results are reported as numerical grades or pass/fail criteria to guide product labeling and quality control.

Importance: Washfastness is a key criterion in textile quality, influencing consumer satisfaction, durability, and care labeling. It affects apparel, home textiles, and technical fabrics; manufacturers may select dye classes and finishing processes to meet required standards.

Improvement: Techniques to improve washfastness include using reactive dyes with optimized fixation, pigment inks with durable binders, and polymer finishes, as well as fixed dyeing processes and careful formulation of detergents. Process parameters and testing must be aligned with target market expectations.