Vat dyes are insoluble substances used for cotton dyeing. The dye is applied in this form, then oxidized by air or oxidizing agents to precipitate the pigment in the fibres. Indigo and anthroquinone dyes are examples of vat dyes. Sulphur dyes are dyes applied by this technique using sodium sulphide solution to reduce and dissolve the dye. Sulphur dyes are used for cellulose fibres.
Disperse dyes are insoluble dyes applied in the form of a fine dispersion in water.
They are used for cellulose acetate and other synthetic fibres. Reactive dyes are compounds that contain groups capable of reacting with the substrate to form covalent bonds. They have high substantivity and are used particularly for cellulose fibres. Oxford University Press 4. All rights reserved.