Determination of the source of strength losses in denim washing

Abstract In denim finishing, washing and bleaching treatments are applied to achieve controlled colour fading. However, these processes may also induce fibre degradation that is not always detectable through conventional mechanical testing. This study investigates the origin of strength losses and chemical damage in denim fabrics using a controlled 3 × 3 × 2 factorial experimental design. Three bleaching types (hypochlorite random, permanganate random, and laccase), three enzymatic conditions (acid cellulase, neutral cellulase, and no enzyme), and two softening levels were evaluated. Chemical degradation was quantified by measuring terminal aldehyde group content as an indicator of oxidative cellulose damage, while breaking strength and colour fading (K/S reduction) were assessed to determine physical performance and visual change. Statistical evaluation was performed using General Linear Model ANOVA with Tukey's post‐hoc test. Bleaching and enzyme type significantly affected aldehyde formation and colour fading, whereas breaking strength differences were not statistically significant. Hypochlorite random bleaching produced the highest aldehyde levels and colour fading, indicating increased oxidative degradation. Laccase resulted in the lowest chemical damage, while acid cellulase caused greater aldehyde formation than neutral cellulase and untreated samples. The results demonstrate that mechanical testing alone may underestimate early‐stage oxidative damage, emphasising the value of integrating chemical indicators in denim process evaluation.