Traditionally all dyes were based on animal, vegetables or mineral sources. In 1856 the first synthetic dyes were produced from coal tar products. Synthetic dyes have a higher fastness, they do not fade or wear as quickly and are are available in a wider range of shades. The cost of dye stuff varies considerably and some products are very toxic. Not all dyes are water soluble and many require the addition of other substances to allow complete dyeing.
There are several types of dyes:
Direct Dyes:Direct dyes are the largest group of dyes, used for cellulose fabrics cotton and viscose. The water soluble dyes are absorbed into them however, they are not fast to washing. Direct dyes are cheap and available in a wide range of shades.
Basic Dyes: When used for wool, the color fastness is poor. They are more important for acryclic fibre. Nylon and polyster have to be modified to accept basic dyes. Brilliant colors are possible.
Acid Dyes: Acid dyes can be used for protein fibres wool and silk, acrclic fabrics, lycra and nylon. They are applied from an acid solution so only fibres that are resistent to acid can be dted by them. They have a wide range of shades but the fastness is variable.
Azoic Dyes: Used primarily for cotton. Azoic dte stuffs produce brilliant fast colors at low cost. The dye is developed on the fabric due to a chemical reaction between two different chemicals which are applied from a low temperature bath. The range of shades is deficient in blues and greens.
Disperse Dyes: These dyes do not dissolve but are applied as a suspension with surface active agents. Disperse dyes were developed for acetate fibre but are now used on man made fibres.
The other dyes include vat dyes, reactive dyes, metal complex dyes and sulphur dyes.
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