A Study of Vat Dyeing on Cotton Fabric Assisted by Zinc as Reducing Agent

Vat dyes are one of the most popular dyes used on textiles particularly on cotton textile materials. This is because of its excellent fastness properties as well as other desired characters needed on cotton garments. However, vat dye is originally insoluble in water. In conventional vat dyeing process, the vat dye is dissolved using sodium hydrosulphite, hydrose which is a powerful reducing agent followed by solubilising with sodium hydroxide. This process creates very high pollution problem. In this study, an attempt has been made to see the effect of zinc metal powder (2% owm) and the combination of zinc metal powder (1.5% owm) with hydrose (0.5% owm) as reducing agent. The results of these reducing agents were compared with those of the conventional vat dyeing with hydrose (2% owm), in terms of different parameters such as strength of the fabric, rubbing fastness, washing fastness, light fastness and effluent parameters.