Naphthol and Fast Bases

Naphthol dyes are insoluble azo dyestuffs that are produced on the fibre by applying a Naphthol to the fibre and then combining it with a diazotized base or salt at low temperature. Azoic combinations are still the only class of dye that can produce very deep orange, red, scarlet and Bordeaux shades of excellent light and washing fastness.

Bases: These are available as free amine salts such as like the hydrochloride. Many of the amines used are simple substituted aniline derivatives with no ionic substituents. The so called Fast colour bases require diazotisation.