ABSTRACT
Subsequently, the synthesis of vat dyes has been an extremely active field of research and many new members of various complex chemical structures were incorporated into this dye-class. The industrial use of vat dyes started at the beginning of 20th century. By 1966, vat dyes accounted for about 26% of all the dyes marketed in the USA and 40-50% of all dyeings on cellulosic fibers. An estimate made in 1979 showed vat dyes to have a 15% share with indigo contributing a further 2%. Vat dye is so-called because indigo was dyed on textiles in wooden vat in ancient days. The old-fashioned method of fermenting and steeping indigo in a vat gave vat dyes their name. They are prepared today on the same principle, but they are chemically purer and the process is shorter. The chemical nature of vat dyes and their method of
application (solubilisation by reduction, rapid penetration into the fiber followed by oxidation into insoluble color) guarantee an exceptional standard of fastness. However, the number of dyes introduced in the range has not increased much after 1968. A survey in Europe showed that out of 207 dyes manufactured in 1984, only 19 dyes were developed during the period 196884.
