The mordanted cotton cloth was immediately
used for dyeing because some mordants are light
sensitive. The chromatophore of the dye makes it
resistant to photochemical attack, but the auxochrome
may alter the fastness. This is due to the formation of
complex with the metal which protects the
chromatophore from photolytic degradation. Wash fastness of the dye is influenced by the rate of diffusion
of the dye and state of the dye inside the fiber.