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Different types of Dyeing process Basic dyes are ionic in nature. They ionize into coloured contains and colorless anions. First of all, Perkin invented this colour. The first member of this class according to his name was Perkin’s mauve. In these dyes the coloured portion (Present in the cotton) is derived from free or substituted amino group such as –NH 2 , –N(CH 3 ) 2 , –N(C 2 H 5 ) 2 etc. These dyes are generally in soluble in water or sparingly soluble in water. The dye base becomes soluble in water when they from hydrochlorides, oxalates, acetates, sulphates etc. Since basic dyes are not easily soluble in water, the best way to dissolve them into paste with water, an equal weight of acetic acid (40%) and then pouring boiling water with constant stirring. If boiling water is directly poured over the dye powder, it forms a tarry mass. Pasting of the dye powders may be done with methylated spirit, in which they are suitable. The dye solution thus prepared should be filtered ...

The first subjective or 'direct' dyes discovered in 1884 were diazo dyes obtained from terazotised benzidine.The direct dyes are called substantive dyes they have strong affinity for Cellulosic fibers.   It was called a direct dye because it was the first dye to become available for coloring cellulose 'directly' without the use of a any other chemical such as mordant. The direct dyes are called substantive dyes as they have strong affinity for cotton and other Cellulosic fibers. Properties: They are available in a full range of hues but are not noted for their color brilliance. They have poor moderate fastness to washing but can be improved by after - treatment with copper salts & cationic fixing agents. The light fastness of with direct dyes on cellulose fibers varies from poor to fairly good, although some copper complex direct dyes have good light fastness.   SDC committee also classified Direct Dye on three categories based on their leveling ability...