Difference between Soluble and Insoluble Vat dyes

Vat dyes are somewhat different from the other type of dyes. Because they are found in insoluble form. The dyeing procedure of vat dye is not as the same as the other dyes like reactive, direct, azoic, acid or basic dyes. Vat dyes are water-insoluble pigments. They are called dyes because chemical reduction in alkaline solution converts the pigment into a water-soluble leuco form with substantivity for cotton. After dyeing with the leuco compound, the pigment is regenerated in the dyed cotton by oxidation.

Though vat dyes are insoluble natural coloring materials, they are available in the soluble form also. Chemically they are sulphuric esters of leuco vat dyes and may be called leuco esters or solubilized vat dyes. There are some visible differences between insoluble and soluble vat dyes.

Insoluble Vat dye

Soluble Vat dye

·       Insoluble in water

·       Soluble in water

·       Naturally obtained coloring materials

·       Obtained by the reaction of insoluble vat dye with sulphuric ester

·       Primarily no affinity for textile fibers

·       Have affinity to textile fiber

·       Have affinity to textile fiber

·       Oxidation is difficult

These dyes are mainly used for dyeing denim or jeans. This dye is used from the ancient times. Dyeing procedure is interesting and somewhat different from the other dyes.

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