Patent ID: 7041143

Claim:
A method of colouring hair, which comprises applying to the hair being coloured, in any order successively, or simultaneously, a capped diazonium compound and a water-soluble coupling component a) under alkaline conditions and optionally in the presence of a further dye, and then subjecting the hair being coloured to treatment with acid, or b) under alkaline conditions, and then subjecting the hair being coloured to treatment with acid, optionally in the presence of a further dye, wherein there is used as the capped diazonium compound an antidiazoate of formula a diazosulfonate of formula a diazine of formula or a cyclic triazene of formula wherein A is the organic residue of an unsubstituted or substituted aromatic or heterocyclic amine and B is the radical of an unsubstituted or substituted, water-soluble aliphatic or aromatic amine, wherein at least one of the above groups must contain a radical imparting water solubility.