Fast bases dyes are available as free amine salts like hydrochloride. The so-called fast bases require diazotization. Fast bases dyes are very economical when used to dye with naphthol. Using fast bases dyes can achieve different color shade which is not possible using other dyestuffs. Fast bases have very good color fastness.

Fast bases dyes are widely used in Textile, plastic, chemical and pharmaceutical industries. Fast bases dyes are great to achieve color shades like blue, orange, yellow, red and other colors which is not possible using other dyestuff. It's also used in African print and wax.

Fast bases dyes are highly sensitive to heat and moisture and always need to store in cool and dry place. Dyeing process of fast bases is done in 2 steps.

Step 1: Material needs to be impregnated with naphthol solution
Step 2: Development takes place with use of a diazotized fast base.