Enzymatic natural dyeing of cotton and silk fabrics without metal mordants

Two step ultrasonic dyeing of cotton and silk fabrics with natural dyes, Terminalia arjuna, Punica granatum, and Rheum emodi have been developed in which an enzyme is complexed with tannic acid first as a pretreatment. This was found to be comparable with one step simultaneous dyeing. The effectiveness of three enzymes—protease-amylase, diasterase and lipase was determined. The enzymatic treatment gave cotton and silk fabrics rapid dye adsorption kinetics and total higher adsorption than untreated samples for all the three dyes. The CIELab values also showed improvement by enzymatic treatment. The tannic acid-enzyme-dye combination method offers an environmentally benign alternative, ‘soft chemistry’ to the metal mordanted natural dyeing.