Compatibility of binary mixture of natural dyes for developing compound shades for cotton khadi fabric

Abstract

The compatibility rating of any two natural dyes applied together for obtaining compound shade has been determined. The natural dyes selected for compatibility study are, babool (BL), pomegranate rind (PR), madder or manjistha (MJ), red sandal wood (RSW), tesu flower (TF) and catechu (CT) based on their maximum commercial use. The dyes have been extracted in aqueous medium under optimized conditions and their binary mixtures in different proportions are used to dye cotton khadi fabric for developing varying compound shades on 15% overall concentration of myrobolan (harda) and aluminium sulphate (75:25) in sequence double pre-mordanted cotton khadi fabric. After dyeing with binary mixtures of natural dyes , dyed cotton fabric samples are subjected to evaluation of K/S, colour differences (∆E), colour difference index (CDI) values; changes in hue /chroma, brightness index (BI), metamerism index (MI) etc; and also colour fastness to washing, light, rubbing and perspiration. The compatibility of these binary pairs of natural dyes has been assessed conventionally (∆c vs ∆L and K/S vs ∆L), as well as using an unique and simple novel method of compatibility test applied for assessing relative compatibility rating (RCR) of each binary pairs of natural dyes, by evaluating colour difference index [(∆E x ∆H) / (∆C x MI)] for application of different proportion of two dyes in each binary pair. The results of this novel simple method are found mostly in well agreement with the findings of compatibility test by conventional methods. Finally, the order of relative degree of compatibility of these binary pairs of natural dyes is found to be BL: MJ > BL: RSW > BL: CT > BL: PR > BL: TF.