Dyeing wool with a sulphur black dye using a sodium borohydride /sodium bisulphite reducing system

Sulphur dyes have been traditionally used for dyeing cellulosic materials, in particular for dark navy and black shades on cotton. This study investigates the feasibility of using the dyestuff CI Sulphur Black 1 as a cost‐effective, metal‐free alternative to reactive and chrome dyes, to produce deep black shades on wool with high fastness levels. The new wool dyeing procedure uses sodium borohydride and sodium bisulphite as the reducing system for the sulphur dyes. Results are presented on the colour parameters, fastness to washing, alkaline perspiration, light, dry and wet rubbing, and wet burst strength of wool fabrics after dyeing with the sulphur dye. The results have been compared with those of wool dyed by conventional methods with a chrome black and a reactive black dye. It has been shown that the sulphur dye can be used to produce a deep black shade on wool that is comparable with that obtained with either a reactive or chrome black dyestuff. With the exception of wet rubbing, the fastness properties are generally similar, or better than, those of the reactive and chrome dyes, but fibre damage is greater. Some further work is therefore required to overcome these two disadvantages.