The effect of humidity, fabric surface geometry and dye type on the colour of cotton fabrics dyed with a select range of anionic dyes

Abstract

Twill and plain woven bleached cotton fabrics were dyed with a trichromatic set of dyes, C.I. Direct Red 243, C.I. Direct Yellow 106, C.I. Direct Blue 85 individually, with different combinations of these dyes and also with C.I. Reactive Red 24. Dyed fabrics were subsequently conditioned at 0, 25, 45, 65 and 85% relative humidity levels to study the effect of various atmospheric humidity levels, expressed by moisture content, on the colour of substrates. A mass balance was performed and dye uptake by the fabric was normalized based on the mass and size of the substrate to minimise error when determining the effect of moisture and fabric surface geometry on colour. Variations in colour between conditioned samples were assessed using two methods: the Δ E ∗ cmc colour difference equation and the summative Kubelka–Munk function. For the same amount of dye present on fabrics, due to increased effective surface area, twill structures exhibited higher increases in their depth of colour than plain woven substrates for any of the relative humidity levels examined. The findings reveal that the moisture absorbed by the fabric from the environment, and fabric geometry, significantly affect fabrics apparent colour and the effect is more pronounced at higher humidity levels.