Dye-fibre association

Sulphur dyes are used on cellulosic fibres to produce form. Sulphur dyes are used on cellulosic fibres to produce dark colours such as black, brown, olive and green. Like vat dyes, they are water-insoluble mixtures that are present in the dyebath as leuco derivatives. These are then oxidised on the fibre to give the desired colour, which is normally very fast to washing.

Azoic dyes, vat dyes and sulphur dyes are three further classes of dye used to dye cellulosic fibres, all by the formation of insoluble compounds in the textile fibres. Azoic dyeing involves the production of an insoluble azo dye on a fibre by the interaction of a diazotised amine and a coupling component. Vat dyes are water-insoluble dyes, usually containing keto (RC=O) groups, which are applied in the soluble reduced form and subsequently oxidized in the fibre to the insoluble form.