Sulfur dyes are applied on cotton to produce deep shades at low cost; they provide excellent color fastness, except against chlorinating agents. Sodium sulfide used as a reducing and solubilizing agent in this dyeing process is highly toxic and produces unhygienic hydrogen sulfide.

Enzyme ( REDUSUL EL ) was used in place of sodium sulfide to see if the latter could be substituted with the former, because of its hydrolytic and reducing nature in an alkaline bath. REDUSUL EL revealed that enzyme was quite effective in this regard and capable of substituting sodium sulfide with comparable dye strength of dyed cotton along with promising color fastness.