Dyeing

Dyeing consists of imparting colour either to the loose cotton fibre, yarn, cloth or manufactured garments. There are two main dyeing techniques: dyes are either applied from dye solutions (yarns, fabric) or by printing from dye pastes (garments). A lot of commonly used dyes contain toxic chemicals which are hazardous to human health and the environment, and need to be specially treated and disposed of after the dyeing process.

Some of the most hazardous chemicals are benzidine, formaldehyde, heavy metals and the so called azodyes. The use of these substances is prohibited or restricted in most developed countries.

Bleaching is the process of whitening cotton with chemicals and is oftenused as a pre-treatment before the dying process. The most common bleaches for textiles are hydrogen peroxide, sodium hydroxide, tensides and chlorine dioxide. The latter is highly hazardous to water ecosystems if left to drain untreated into rivers.