Investigations of the colourimetric and fastness properties of wool dyed with colorants extracted from Indian madder using reflectance spectroscopy

In this study, the natural anthraquinone colorants extracted from madder roots were used to develop beautiful hues on wool fibres. Wool dyeing with colorants from natural sources has some limitations such as low color strength and fastness properties. Therefore prior to the dyeing with Indian Madder (Rubia cordifolia) wool fibres were pre-treated with different concentrations of potassium aluminum sulfate metal salt (viz 5–1% o.w.f). Reflectance spectra’s of dyed samples were measured using spectrophotometer at the wavelength of maximum absorption (λmax 450 nm) under D65 illuminant (10° observer) in order to obtain color characteristics and K/S values. The effect of alum mordant on color fastness to light, rubbing and washing were determined according to standard ISO and AATCC test methods. According to the experimental results, the color coordinates of dyed woollen yarn samples were found in the red-yellow quadrant of CIELa*b* color space diagram. Results of color characteristics and fastness properties demonstrated that mordanting with 5% potassium aluminum sulfate enhanced the color depth as well as fastness to light, washing and rubbing.