Vat dyeing at room temperature

Traditionally, naturally extracted Indigo has been used for dyeing cotton. Amongst all the classes of dyes for cellulosic material, vat dyes are most widely used due to their excellent fastness properties. The vat dyeing process, depending upon the subclasses, has to go through reduction phase for solubilisation, dyeing and oxidation phases at specific conditions. Even with the advent of new techniques like the electrochemical and bacterial process, their industrial use is relatively limited. Prior investigation on bacterial reduction suggests only a few possible varieties of indigo-reducing bacteria, sources of most of which are still unknown. Also to implement this processes, they are required to be performed at higher temperatures. In the present study, we have developed a novel method of vatting and dyeing using bacterial cell lysate at room temperature followed by air oxidation. This paper also compares the newly proposed processing route with the existing conventional ones, and the experimental results have shown promising results regarding improvement in dye uptake, faster dyeing, and better levelness along with their fastness properties. Besides, the proposed process ensures energy saving, dye effluent load reduction and simplifies the existing process.