General Nature Of Vat Dyes: Explained Completely
by : Rahul Sharma
GENERAL NATURE OF VAT DYES:
Vat dyes are sold as water insoluble pigments, so why are they called dyes? Like all other dyes, under the right circumstances, they can:
- Be dissolved to give solutions containing individual molecules or molecular ions,
- Be transported to the surface of the fiber and
- Be sorped on and diffuse into suitable fiber.
Vat pigments need alkaline reduction to dissolve them, and they are treated to an additional step (oxidation), which causes the original insoluble pigments to be regenerated, once the soluble ions have diffused within the fiber. Nevertheless, the third step, the sorption and diffusion of suitable derivatives of vat dyes into cellulosics, parallels that of direct dyes quite closely.
One of the keys to successful dyeing with vat dyes is to have control over how and when to convert the pigmentary colors into water soluble coloring chemicals, under conditions in which they will diffuse uniformly into the fibers.
