Introducing variations in colour of cotton fabric–reactive dye systems through irradiation with a carbon dioxide laser

The effect of CO 2 laser treatment before dyeing (LD) and after dyeing (DL) was compared in terms of colour variation. Two reactive dyes, CI Reactive Blue 19 (RB19) and CI Reactive Black 5 (RB5), were used in three concentrations −0.1, 1, and 5% owf. Morphological changes of the fabrics after laser treatment were observed using a scanning electron microscope. Chemical modification of the laser‐treated cotton fabrics was detected using attenuated total reflectance Fourier transform infrared spectroscopy. The difference in colour was evaluated by spectrophotometer; reflectance value, colour yield, CIE L * a * b *, and levelness were determined. The tensile strength of fabrics laser treated before and after dyeing was also measured. The results show that the DL approach has a stronger effect, resembling a fading of colour, yet a higher tensile strength, especially when dye RB5 is used. The LD approach, on the other hand, provides a better colour yield, levelness, and tensile strength when dye RB19 is used.