Process for the application of dye fixing agents to polyamide fiber utilizing controlled fixing agent addition

A process for increasing the washfastness of a fibrous article containing polyamide fibers dyed with anionic dye by treatment with an anionic dye fixing agent. The process includes immersing the article in a liquid bath of either an aqueous or substantially nonaqueous solvent medium for the fixing agent and heating to a temperature at least equal to the dyeing transition temperature of the fiber. The fixing agent is added to the bath so that the rate of fixing agent addition to the bath is the primary control over the rate of fixing uptake by the article at the early stages of aftertreating. In the later stages, the rate of fixing agent addition controls the concentration in the bath whereby the propensity for the fixing agent to agglomerate from the bath is decreased.