Science and Technology 2015, 5(2): 26-32 DOI: 10.5923/j.scit.20150502.02 Effects of Selected Mordants on the Application of Natural Dye from Onion Skin (Allium cepa) Abdu Zubairu * , Yusuf Madu Mshelia Department of Chemical Engineering, University of Maiduguri, Borno State, Nigeria Abstract 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. Keywords Onion Skin, Natural Dye, Mordant, Cotton Fibre 1. Introduction The art of dyeing is an ancient practice. For instance, it was in use during the Bronze Age in Europe, were common dyeing techniques include sticking plants to fabric or rubbing crushed pigments into cloth. These methods were later developed, leading to sophisticated techniques using natural colours from crushed fruits, berries and other plants, often boiled into the fabric to enhance light and water resistance property of the fabric [1]. The art of dyeing therefore, could be said to have stems from the use of natural dyes. Natural dyes are thus regarded as all colours and dye pigments derived from plant, animal or insect matter without any chemical processing [2]. Dyeing textile materials; natural or synthetic, is aimed to add value, improve look and enhance product desire of the customers. As pointed earlier, this purpose of colouring textile was initiated using colours of natural source. However, the use of natural dyes subsequently diminish with the invention and commercialization of synthetic dyes. In addition, the ready availability of pure synthetic dyes of * Corresponding author: abduzubairu@yahoo.com (Abdu Zubairu) Published online at http://journal.sapub.org/scit Copyright © 2015 Scientific & Academic Publishing. All Rights Reserved different types or classes and their cost advantages, propelled most textile dyers and manufacturers to shift towards the use of synthetic colourants. Almost all the synthetic colourants were being manufactured from petrochemical sources through hazardous chemical processes which poses serious threat towards their eco-friendliness [3]. Few natural dyes are colour-fast with fibres, therefore the use of mordants which increases the dye fastness to the fabric is often necessary. Mordants are essentially substances which are used to fix a dye to the fibres, they also improve the take-up quality of the fabric and help improve colour and light-fastness. Mordants are usually metallic salt of aluminium, chromium, iron, copper and tin, as well as other substance such as tanning agents. Mordants found in nature include wood ash, stale urine and acidic fruits extracts such as lime [1]. The use of mordant in dyeing not only increase the dye take up and colour fastness but the use of different mordant on a natural dye can yield different colours and shades. Detailed comparisons of the advantages and disadvantages of natural dyes relative to synthetic dyes were presented in previous literature [3]. Recently, dyes and colours of natural origin are gaining worldwide recognition as substitute for synthetic dyes in textile manufacture, for colouring of food products, cosmetics and pharmaceutical products [4]. This renewed