The effects of bio‐mordants and metal mordants on colour sensitivity in wool dyeing with natural dyes

The colour strength and colour sensitivity of a dyebath are important indicators for evaluating the dyeing behaviour of a dye and controlling the dyeing process. In this study, the effects of bio‐mordants and metal mordants on the colour sensitivity in wool dyeing with madder, weld and pomegranate natural dyes were investigated. For this purpose, madder, weld and pomegranate peel natural dyes were extracted using the ultrasonic probe method; then the wool yarn was dyed with these natural dyes in different depths with walnut as a bio‐mordant and alum as a metal mordant using the premordanting method. To evaluate the dyed samples, their reflectance spectra and colour parameters were measured. The colour sensitivity of the dyeing recipe was evaluated by measuring the Color Measurement Committee colour difference and calculating the colour sensitivity coefficient resulting from a 10% change in the parameters of the dyeing recipe such as dye concentration, mordant concentration, temperature, time, pH and the liquor ratio of the dyebath. Additionally, colour sensitivity was measured for simultaneous changes in six parameters. The results obtained indicate that the colour sensitivity of metal mordant is greater than that of bio‐mordant. The colour sensitivity with respect to temperature is greater than that of the other parameters. The colour sensitivity of madder natural dye is greater than that of weld and pomegranate natural dyes. The colour sensitivity at low colour depth is greater than that at high colour depth. The statistical analysis indicates that colour sensitivity depends on the dye type and colour depth.