TERNARY NATURAL DYE MIXING: CACTUS, TURMERIC, AND BASIL EXTRACTS FOR SECONDARY SHADES VIA MICROWAVE EXTRACTION

Abstract

A recurring limitation of single-source natural dyes is their restricted colour palette, which has motivated researchers to mix two or more natural colourants in a single bath to generate secondary shades; however, this practice has been reported almost exclusively for binary (two-source) combinations. This study examined whether extending this approach to a ternary (three-source) combination, cactus pear fruit (Opuntia ficus-indica), turmeric root (Curcuma longa), and basil/tulsi leaves (Ocimum tenuiflorum), could yield a distinct secondary shade on cotton with acceptable rubbing fastness, using a single microwave-assisted extraction bath. All three sources were extracted together in a domestic microwave oven and applied to cotton strips both with and without an alum mordant, and the resulting dry and wet rubbing fastnesses were compared to each other and, by cross-reference, to the single-source fastness values reported for the same three dyes in a companion study. The unmordanted blend showed good dry rubbing fastness (4-5 GS) but poor wet rubbing fastness (2 GS); alum mordanting raised the wet fastness only marginally, to 3 GS, while leaving dry fastness unchanged. Rather than averaging the fastness of its constituents or inheriting the best-performing source's wet fastness (cactus with alum, 5 GS), the blend's wet-fastness ceiling tracked its weakest single-source component (turmeric with alum, 2 GS), suggesting that combining natural dyes in one bath does not straightforwardly combine their individual durability advantages. The study reports a microwave-extracted ternary natural dye blend evaluated for rubbing fastness on cotton, and it offers a low-cost, single-bath protocol together with an honest account of the limited (n = 1 per condition) evidence base underlying these findings.