Investigation into the Colouration of Wool with Indigo

Abstract

This paper describes the colouration of wool with indigo. The wool fabric is pre-treated with different shrink-resist formulations followed by application of indigo. The novel dyeing procedure has resulted in commercially acceptable indigo-dyed wool, in terms of improved levelness and reduced yellowness. While indigo is traditionally applied by the padding technique, in the present work, an exhaust dyeing procedure is investigated. The degree of levellness and the depth of shade are further optimised by varying the pH, temperature and dye concentration. The pH of the dye liquor and the dyeing temperature are found to be critical in achieving level dyeing as well as mitigating fibre damage. It is found that certain shrink-resist formulations, either applied alone or in combination, give better results in terms of colour yield and fabric handle, while other combinations give poorer results. The dyed samples are found to exhibit excellent wash fastness.