Extraction of natural dyes from the stem of Caulis spatholobi and their application on wool

Researchers are continuously exploring new candidates in the field of natural dyeing to lighten the burden of synthetic dyestuff on living organisms. In this research, novel natural dye was explored using the Caulis spatholobi plant. The extraction was carried out through the conventional extraction method in the aqueous medium. Various parameters of the natural dye extraction process, such as the material-to-liquor ratio, pH, time and temperature, were optimized to 1:40, 12, 120 min and 100℃, respectively. The extract was filtered twice and used for the characterization and dyeing of wool fabric. The extract was characterized using Fourier transform infrared spectroscopy for the determination of dominant functional groups. Natural dyeing of wool was carried out with and without metal mordants, such as aluminum sulfate, ferrous sulfate, copper sulfate and zinc sulfate. Pre-mordanting, meta-mordanting and post-mordanting techniques were employed. The performances of dyed fabrics were evaluated in terms of color strength K/ S values. The fastness properties of dyed fabrics were also measured. The dyed fabric showed various color shades based on the type of mordant used. Furthermore, enhancement in the colorfastness was observed with mordanting.