Coloration of cotton fibers with natural plant dyes using an overlay dyeing method

Dyeing of cotton fibers using dyes extracted from natural plants is considered to be environmentally friendly. Herein, three kinds of plant powders including turmeric(Curcuma longa L.), gardenia(Gardenia jasminoides J. Ellis), and Cotinus coggygria(Cotinus coggygria Scop.) were employed to extract colorants in ethanol and aqueous solutions. Then cotton fibers were dyed in the solutions of extract colorants in the presence of mordants using an overlay dyeing method. The effects of the extraction method and mordants on the color of the extract were analyzed using UV-Visible absorption spectroscopy, and structural changes in the dyed cotton fabrics were investigated. The dyeing and physical properties of the cotton fabrics following overlay dyeing with natural dyes were analyzed, and the cotton-dyeing mechanism was revealed. The water extracts provided better dyeing effects than the ethanol extracts, and color indices, such as the K/S, a*, and b* values, and the color fastnesses of the dyed fabrics obtained by overlay dyeing were strongly influenced by the type of natural dye used in the final dyeing step. Cotton fabrics prepared by overlay dyeing with ethanol-extracted natural dyes also exhibited antimicrobial properties.