Colour Fastness in Cotton Fabric Dyed with Cochineal.

In ancient cultures, dyes were obtained from nature used for their diverse activities, until in 1856, when Perkin oxidized aniline. Since then, synthesis of an infinite number of synthetic dyes began. Main advantage of these dyes is their low price; however they are harmful to human. Therefore these products are considered pollutants to the environment. Many industries are looking for a way to substitute synthetic dyes for natural dyes. Previous studies developed in our laboratory, had shown that cochineal extract has a good potential to replace synthetic dyes on cotton dying. Nevertheless, its durability on fabric wasn't tested. To verify constancy of color on cotton fabric dye with cochineal, five stability tests were performed. Dye fabric with cochineal was exposed to different pH solutions (acid and basic); temperature (5 and 60 °C); exposition to artificial light; washing test (with different detergents) and crockmeter test. Color was analyzed before and after of each stability test and was determined with a colorimeter using the Cielab scale. Results showed that dyed fabric have a good stability at pH solutions, low temperature, exposition to artificial light and crockmeter test. It had a poor stability at high temperature and to different detergent used. These results support our hypothesis to use cochineal as alternative to replace synthetic colorants in textile industry.