Dyeing process for keratin materials, with improved exhaustion of bath constituents

A method of applying dye to keratin fibres comprising pretreating the fibres by contacting them with a bath liquor comprising an alkaline solution of an amphoteric surfactant, and thereafter adding dye to the bath liquor and applying the dye to the fibres from said bath liquor, wherein said amphoteric surfactant comprises an alkoxylated hydroxysulphobetaine of general structure:

• ##STR16## where:
• R.sub.1 is a hydrocarbon group selected from the range C.sub.12 H.sub.25 up to C.sub.21 H.sub.43 ;
• R.sub.2 and R.sub.3 are poly(alkylene oxide) groups, each having n alkylene oxide units, where 3.ltoreq.n.ltoreq.21;
• wherein said bath liquor is substantially deficient of any surfactant-type levelling agents other than alkoxylated hydroxysulphobetaine of said structure;
• and
• wherein said bath liquor is a single bath liquor which is initially said alkaline solution for said pretreating step and then is converted to a dyeing solution for the dye applying step by said adding of dye to the bath liquor.

A method of applying dye to keratin fibres comprising contacting said fibres with a dyebath liquor including one or more insect-proofing agents and an amphoteric surfactant levelling agent which comprises an alkoxylated hydroxysulphobetaine of general structure:

• ##STR17## where:
• R.sub.1 is a hydrocarbon group selected from the range C.sub.12 H.sub.25 up to C.sub.21 H.sub.43 ;
• R.sub.2 and R.sub.3 are poly(alkylene oxide) groups, each having n alkylene oxide units, where 3.ltoreq.n.ltoreq.21;
• wherein said dyebath liquor is substantially deficient of any surfactant-type levelling agents other than alkoxylated hydroxysulphobetaine of said general structure.