抄録
Shikon, root of Murasaki plant, is well known as one of the earliest natural dyes, but it seems that its wide-spread use has largely been limited due mainly to the two inherent difficulties involved in dyeing.
First the Shikonin dyes in root, responsible for its purple color exhibition, are originally water-insoluble, since they are in the form of ester, while many other vegetable dyes are often found as aglycon accompanying some solubility. Secondly the purple color of Shikon often fades rather quickly.
We have shown that the first problem can be conveniently overcome by applying organic solvent in the extraction process and mixing it with water in dyeing. The best composition of dyeing was found through experiments at 4/6 of ethanol in water by volume ratio.
Regarding the color fastness on dyed cloth, we have also shown that the ruling factor is temperature. Color on dyed cloth changes markedly if the extraction temperature exceeds over 60°C. Although the structual changes due to heating may be attributable to a reaction at the double bond of side chain, enough proof has not been given at this stage.
Moreover mordant dyeing with various metal ions and the effect of pH in dye bath are experimentally examined.
