Resistance to fading; i.e., the property of a dye to retain its colour when the dyed (or printed) textile material is exposed to conditions or agents such as light, perspiration, atmospheric gases, or washing that can remove or destroy the color. A dye may be reasonably fast to one agent and only moderately fast to another. Degree of fastness of colour is tested by standard procedures. Textile materials often must meet certain fastness specifications for a particular use.