Comparative performance analysis of oxidative and alkaline spray treatments as alternative garment dry processes for indigo‐dyed denim: Effects on colour fading and physical properties

Spray techniques have gained widespread applications in denim garment dry processes for obtaining controlled fading and vintage effects in terms of colours. The impacts of chemical sprays on the chromatic and physical properties of the denim fabric need to be analysed before optimising the process. In this research, the effect of an oxidative potassium permanganate (KMnO 4 ) spray and calcium hypochlorite [Ca(OCl) 2 ] as well as alkaline sprays comprising sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide [Ca(OH) 2 ] spray treatment on indigo‐dyed denim fabric samples at concentrations of 5, 10 and 15 g/L has been analysed. The effect of chemical spray treatments on factors such as chromaticity, L*, reflectance % (R%) and warp shrinkage was found to be statistically significant using one‐way ANOVA test, while that on tensile strength and areal density was statistically insignificant. The KMnO 4 spray treatment resulted in a significant colour‐fading effect but caused comparatively more structural change in fabric because of the oxidising nature of KMnO 4 . The NaOH and KOH sprays resulted in good performance with reasonable strength retention and vintage effect on denim surface, and the Ca(OCl) 2 spray yielded acceptable results regarding visual colour‐faded properties along with structural changes. Of all the spray treatments, the Ca(OH) 2 spray showed optimum performance. This research can assist while improving denim garment dry processes as KMnO 4 spraying may be preferred when strong colour fading and worn‐out effect are required, while alkaline spraying may be preferred when moderate colour fading is required along with optimum properties.