Finishing of denim fabrics with ozone in water

Traditionally, denim has a white cotton weft and a dyed cotton warp with twill weave. Usually, the warp yarn is ring dyed where the dye is concentrated, as layers, on the surface of the yarn rather than diffused inside of the yarn. This phenomenon is exploited in the different finishing treatments of jeans where the aim is to partially remove the dye from the surfaces of the warp yarns to expose the lighter core of the yarns. In addition, the finishing treatments are used to remove sizing agents and to make the jeans softer and more comfortable. The stone wash with pumice stones is nowadays mostly replaced by the treatment with cellulase enzymes.1 During the enzyme treatment, the mechanical action in the washing drum, fabric-fabric friction and slight swelling of the outermost layers of wet cotton fibres increased the accessibility of cotton to enzymes and allowed the removal of dyes and caused desired fading and softening of the denim jeans.2,3 In addition to cellulases, laccases have been studied in the finishing of indigo dyed denim fabrics and they were found to degrade indigo both in solution and on denim successfully.4,5 It is commonly known that the denim fabrics are prone to be affected by the removed indigo during the desizing and enzyme treatment phase. The removed indigo dye is redeposited on the fabric which diminishes the look of the fabric, and is known as backstaining.6–8