Light fastness of naturally occurring anthraquinone dyes on nylon

Nylon fabric has been dyed with two purified components of Indian madder, purpurin (1,2,4‐trihydroxyanthraquinone) and munjistin (1,3‐dihydroxy‐2‐carboxyanthraquinone). The light and wash fastness of dyed and mordanted samples has been studied. Purpurin showed much better resistance to photofading than munjistin. It was found that the type of mordant and the method of mordanting significantly affected the rate and extent of photofading. The use of copper or ferrous sulphate gave high resistance to fading, whereas stannous chloride or alum did not. On the other hand, light fastness was improved when postmordanting was conducted with copper or ferrous iron, but pre‐mordanting was superior in the case of stannous chloride or alum.