Natural dye extracted from Chinese gall – the application of color and antibacterial activity to wool fabric

A natural dye has been extracted from Chinese gall and its dyeability of wool fabric has been studied together with its colorfastness and antibacterial performance. A fractional factorial experimental design using Taguchiʹs orthogonal array was undertaken to determine the optimum extraction conditions of a 90 °C temperature, a 1:30 liquor ratio and two extraction cycles each 60 min long. The extracted dye liquor was then used in a second orthogonal design of experiment to determine the optimum pre-mordant dyeing conditions on wool fabric. Under these conditions of 200% dye liquor concentration, 2.5% mordant concentration, pH 8 and 98 °C, the colorfastness of the optimum dyed fabric to washing, crocking and perspiration were found to be all acceptable with at least a Grey Scale rating of 3. Antibacterial activity of this dyed wool was confirmed by exposing the fabric to Staphylococcus aureus and Escherichia coli. The fabric dyed with Chinese gall extract reduced the number of viable organisms by 99.90% and 96.55% respectively. The market evaluation and cost of Chinese gall have been analyzed. The economic benefit for Chinese gall was acceptable and can be used in dyeing and antibacterial finishing of textile materials.