PURPOSE: To simultaneously impart durability, excellent color fastness to light and abrasion resistance to a fiber structure by immersing the fiber structure in a treating agent comprising an aqueous urethane resin and a stabilizer for the urethane resin and subsequently heating the treated fiber structure.

CONSTITUTION: A fiber structure is immersed in an aqueous treating bath compounded with aqueous urethane resin of blocked polyisocyanate prepolymer type and with a stabilizer for the resin, such as 6-hexanemethylene-bis-(N- dimethylsemicarbazide) in an amount of ≥10wt.% based on the resin, followed by heating the immersed fiber structure to form a stable coat on the fiber structure, thereby improving the aging deterioration, touch deterioration and color-fading inclination of the fiber structure and further improving the color fastness to light and abrasion resistance of the fiber substrate itself. The method provides a good result when applied to the dry cleaning process of high grade fiber products such as silk.