Studies on Compatibility of Binary Mixture of Natural Dyes for Developing Compound Shades for Khadi Cotton Fabric

The main objective of this part of the present work was to develop and verify an easy method of determining compatibility rating of any two dyes to be used in pair in combination for dyeing of cotton khadi fabric with natural dyes for obtaining compound shades. Each of the natural dyes taken here e.g. Madder or Manjistha (MJ), Pomegranate rind (PR), Babool (BL), Red Sandal Wood (RSW), Tesu Flower (TF) and Catechu (CT) were extracted in aqueous medium at optimized conditions and their binary mixtures in different proportions were then applied on cotton kahdi fabric for developing varying compound shades. Varying proportion of binary mixtures of aqueous extracts of Madder or Manjistha (MJ) with each of the above said other natural dyes taken, have been used to dye bleached cotton khadi fabric after pre-mordanted with 15% myrobolan and potash aluminium sulphate (at optimized concentration and conditions of mordanting for dyeing cotton with madder (manjishtha). After dyeing so, dyed cotton fabric samples were subjected to evaluation of variation in depth of shade/hue /chroma, etc in terms of surface colour strength (K/S value) and its coefficient of variation, brightness index (BI), change in hue (∆H), metamerism index (MI), total colour differences (∆E) and also test of colour fastness to washing, light, rubbing and perspiration. The compatibility of these binary pairs of natural dyes has been assessed conventionally by rate of dyeing of each natural colour and also by the analysis of ∆C vs ∆L and K/S vs ∆L plots as well as by applying varying concentrations of the binary pairs of dyes taken in 50:50 ratio. In this paper, an unique and simple method of assessing relative compatibility rating of pairs of natural dyes has been assessed by evaluating colour difference index [(∆E x ∆H) / (∆C x MI)]. The results of this newer CDI calculation based simple and unique system of determining compatibility rating of binary pair of natural dyes are found mostly in well agreement with the results of compatibility test by conventional methods of ∆C vs ∆L and K/S vs ∆L plots analysis for progressive development of shades. Finally, the order of relative degree of compatibility of these binary pairs of natural dyes is MJ:BL>> MJ:TF >> MJ:RSW >> MJ:CT >> MJ:PR