Acid Dyes are used for dyeing protein fibers. The main protein fibers used for which acid dyes are used are wool, angora, cashmere and silk. Apart these, milk protein fibres like Silk Latte, Soya Protein etc., can also be used.
It has a scary sound to some novices that seems to be due to strong caustic soda. But, in reality these dyes are non-caustic acids and in some cases, these are also non-toxics also. In fact in some cases mild acids like vinegar are used in the dyeing process. Some such mild acids are more toxic than the fiber reactive dyes and some are less toxic and even safer to eat.
There are following categories of Acid Dyes:
Levelling Acid Dyes
The different trade names of levelling Acid Dyes are Kiton, Erio, Sandolan and Amacid, among others. But, it is hard to say that which specific Acid Dyes fall into which of these dye classes.
Levelling Acid Dyes or Strong Acid Dyes are those kind of acid dyes which produce similar, single color solid effects. The condition is that items that are dyed with levelling acid dyes should not be machine dyed or should not be washed in warm water. Instead of this, these should be washed in cool water through dry-cleaned or hand washed.
Milling Acid Dyes
The wet fastness of these dyes are medium to high range. Some Milling Acid Dyes have bad light fastness in pale shades. These dyes are generally not combinable with other dyes. These dyes are mainly used for self shading.
Super Milling Acid Dyes
Super Milling Acid dyes have higher neutral dyeing affinity, better coverage of dye uptake differences in the substrate. Milk protein fibers like Silk Latte, Soya Protein etc., can be used for dyeing through these Super milling acid dyes. These dyes are extremely versatile and the least toxic among all others Acid Dyes.