Investigation of Waste Tea Leaves (Black) as a Source for a Potential Colouring Agent for Textile Substrates for the Sri Lankan Textile Industry

Abstract

Until the invention of synthetic dye “Perkin Mauve” (1856), people used natural sources likestem, bark, leaves of plants etc and for dyeing of clothes. In todays context people areconcerned about the harmful effect of using synthetic dyes and is going for natural dyesinstead. This is a result of the stringent environmental standards imposed by many countriesin a response to the toxic and allergic reactions associated with synthetic dyes. The textileindustry is an important economic activity with a 70% contribution to the Sri Lankaneconomy. Dyes are an important process requirement for which the country spends about 8.5mn US$ annually. Almost all dyes presently used for textile dyeing purposes are of syntheticorigin that are imported to the country.

Some work on the application of tea on wool, silk jute and cotton are available in theliterature (Vankar P.S., 2006). Applications of tea extracts on wool using acetone as thedyeing medium are also reported in the literature. Recently an exhaustive review on thesubject of natural dyes in textile applications has been published by Taylor. In this work,natural tea was used to dye cotton fabrics. The colour of the tea leaves was extracted usingwater as extraction medium. The dyeing was carried out with the dye extracted from wastetea leaves. Washing fastness, light fastness etc, were compared for dyeing carried out usingthe pre-extracted dye. The effect of mordanting in such dyeing was also investigated andcompared.

The present investigation was carried out to revive the old art of dyeing with a natural dyeobtained from tea leaves (Camelia sinensis). It belongs to the family Theaceaee, and iscommonly known as tea and is a crop plant in Sri Lanka. The dye has good scope in thecommercial dyeing of cotton in textile and garment industry. In the present study cottonfabrics were dyed with an aqueous extract of waste tea leaves (black), containing tannins asthe main colourant species. The dyeing was carried out without and with metal salts (Coppersulphate) and natural mordants such as Sepalika (Nyctanthes arbor-tristis), Aralu (Ailanthusexcelsa). Their fastness properties were investigated. The wash, rub and light fastness of thedyed fabrics were good to excellent. Aqueous extracts of tea yield brown shades with goodwash and light fastness on cotton fabrics. All the fastness properties can be further improvedby treatment with certain metal salts and bio materials as mordants. A range of attractivecolours were produced by the use of extracst of waste tea leaves.