400-404A series of homologous alcoholic solvents
and their mixtures has been used for the extraction of coloring matter from
ratanjot (Onosma echoides) powder. The extracted coloring matter is then
used for dyeing of wool and polyester fabrics. The dyebaths are prepared based
on aqueous, solvent and solvent assisted dyeing mediums. It is found that as
compared to a single solvent, a mixture of solvents results in higher
extraction of colorants from ratanjot. Also, the depth of shade reduces with
increasing hydrophobicity of the dyeing medium using the same extraction
medium. While the fastness to washing (change in color) is found to be good to
excellent (3-5) on polyester, it is rather low (1-3) on wool. This can be
attributed to the hydrophobic nature of colorants extracted from ratanjot,
which resemble disperse dyes and have poor wash
fastness on wool but show good wash fastness on polyester