Application of the two-constant Kubelka–Munk theory for predicting the colour of wet nylon fabrics as a function of water content

Fabric wetting is an important factor affecting the colour of fabrics. This work investigated the influence of water content on the colour and reflectance of nylon fabrics dyed with acid dyes. For this purpose, nylon fabrics were dyed with a single dye and a mixture of three acid dyes as Acid Red 361, Acid Blue 225, and Acid Yellow 110 at concentrations of 0.5%, 1%, 1.5%, and 2% O.W.F. Then, the dyed samples were conditioned at water content levels of 0–5%, 20%, 40%, 60%, and 80%. The reflectance spectra and colour parameters of the wet and dry samples were measured using a spectrophotometer. Additionally, the lightness (L*), colour depth (K/S), CMC colour difference, unit k/s, and α-coefficient (the ratio of K/S in the wet state to that in the dry state) were evaluated. The obtained results indicated that lightness (L*) decreased with increasing water content, while the colour difference between wet and dry samples, the α-coefficient, and colour depth (K/S) increased with increasing water content. The effect of three critical factors, water content, shade, and dye concentration, on colour depth (∑K/S), colour difference, and α-coefficient was evaluated using the statistical factorial design method. The ANOVA results indicated statistically significant associations between water content, shade, dye concentration, and colour depth (∑K/S), colour difference, and the α-coefficient. Afterward, the reflectance spectrum of the wet state was investigated from the reflectance of the dry state using the α-coefficient. The accuracy of wet state reflectance prediction depended on relative water content.