Effects of Selected Mordants on the Application of Natural Dye from Onion Skin (Allium cepa)

摘要

Colouration of fabric is a major process in the production of textile material. In this work, natural dye was extracted from onion skin and used to dye cotton fabrics using selected synthetic and natural mordants. The synthetic mordants considered in this work are potassium dichromate, iron sulphate, copper sulphate and alum whereas the natural mordants are aloe vera and lemon. Cotton fabrics were dyed using each of the selected mordants under three different conventional mordanting techniques; pre-mordanting, simultaneous-mordanting and post-mordanting, adopting the well-known vat dyeing method. A wide range of soft and light colours were obtained using the various mordants considered, also the mordanting technique was found to influence the results of the dyeing process. Natural mordants gave pale yellow colours, while synthetic mordants such as copper sulphate and alum also gave yellow colours. On the other hand, iron sulphate gave darker shades of colours. The dyed fabric samples were allowed to age for a week and then washed in standard industrial detergent solution. The wash offs from the samples were assessed for dye bleeding using the conventional photo-sphectrometric method. The absorbance and transmittance measurements were conducted using spectrophotometer at 420nm, and the reflectance evaluated. The colour fast of the wash offs was evalutated using the Kubelka-Munk equation. It was concluded that onion skin dye with iron sulphate as mordant under post-mordanting technique gave the best result of colour fast of the onion skin dye.