Acid dyes are classified primarily on the basis of their dyeing behavior, particularly in relation to dyeing pH, their ability to migrate during the dyeing process, and their wash fastness. The molecular weight and degree of sulfonation of the dye molecules determine these dyeing properties. The classification is based on staining behavior as shown below –
leveling dyes
fast acid dye
Milling Acid Dye
super milled acid dyes
Fulling is the process of treating woolen material in a slightly alkaline solution, in which the role of the machinist is considerable to promote felting. Dyes with good grinding fastness are important to prevent bleeding during dyeing.