Denim and its various items like pants, shirts, jackets, belts, caps, etc, are the most preferred clothing for todays youth. This study discusses compositions and methods of reducing or preventing back staining of indigo dyes on the weft yarn and pocket of denim garments. The dye, as it is removed from the denim material, post treatment with cellulase or by a conventional washing process may cause back staining or re-deposition on the denim material; e.g.: re-colouration of blue threads and blue colouration of white threads, resulting in less contrast between the blue and white threads.
Denim garments are looked at as a major trend setter by our youth. The spread of denim culture all over the world brought with it a trend of fast changing fashions. One after another several washes were introduced such as stone wash, acid wash, moon wash, etc. Over the last decade, India has probably seen the most dramatic and exciting changes in the washing of denim garments. As per the denim garment export market, this high quality garment has superior aesthetics and great value for price. In terms of the quality aspect, back staining plays a vital role in improving the appearance of the denim garment.
Back staining: Back staining implies soiling of the weft thread and the pocket lining by detached indigo or its reduced leuco form. Back staining mainly occurs during desizing or stone washing or enzyme stone washing.
Chemistry of Back Staining:
During stone washing or enzyme washing, cellulose is degraded and indigo dye is released. For instance, the cellulase enzymes are temporarily bound to the cellulose by means of an anchor. This gets split in terms of 1,4-β glycoside composition. After this process it is made available for further hydrolysis reaction.
Enzyme-catalyzed hydrolytic dissociation of cellulose
This reaction is much more complicated in detail, as the customary cellulase consists of several components. Below you can see the dissociation of cellulose in detail: