| abstract |
Method for dyeing hair with azo development dyes comprises applying to the hair a cream of pH about 4.5 contg. a coupler (I) and a diazonium salt (II). When the cream has penetrated the hair sufficiently, a shampoo of pH about 9 is applied to render the dye compsn. on the hair alkaline so that coupling occurs. The hair is then thoroughly rinsed and dried. (I) is imidazole; 2,4-dihydroxyquinoline; dimedone; 1,2-pyrido-4,6-dioxopyrimidine, 1,3-indanedione or esp. 2-amino 3-hydroxypyridine (Ia). (II) is pref. a stabilised monoamine deriv., and the initial cream pref. contains 0.2-10(1-5) wt.% (I) plus (II) (on the basis of the total compsn.) The method is simpler (fewer stages) than the known method in which (I) and (II) are applied separately. |