Method for colouring hair including pretreatment

1. A method for colouring hair comprising:

carrying out the following sequence of steps:

a) in advance of coloring the hair, pretreating the hair with at least one non-polymeric primer composition to form modified hair,

wherein the non-polymer primer composition comprises an oxidizing agent in combination with a pH of at least 9 and a surfactant, and the non-polymer primer composition does not comprise a dyestuff, a chromophore, a fluorophore, an oxidative dye primary developer, an oxidative dye coupler or a direct dye,

b) optionally repeating step a) at least once,

c) treating the modified hair with a hair colouring system comprising a first composition having a pH of from 7 to 9 and at least one cationic polymer having at least one covalently bonded pendant and/or in-chain chromophore and/or fluorophore to form a cationic polymer layer on the modified hair,

d) overlaying the layer of cationic polymer on the modified hair with a second composition having a pH of from 5 to 6 and at least one anionic polymer optionally having at least one covalently bonded pendant and/or in-chain chromophore and/or fluorophore to form a dual polymeric layer on the modified hair.

2. The method according to claim 1 , wherein the surfactant is selected from the group consisting of a cationic surfactant, anionic surfactant, non-ionic surfactant and amphoteric surfactant, and combinations thereof.

3. The method according to claim 2 , wherein the surfactant is an the amphoteric surfactant selected from the group consisting of betain, sultaines, phospholipids, aminopropionates, aminoglycinates, amphoacetate, amphodiacetate, amphopropionate, amphohydroxypropylsulfonates and combinations thereof.

4. The method according to claim 1 , wherein the oxidizing agent is present in an amount ranging from 0.1% to 12% by total weight of the primer composition.

5. The method according to claim 1 , wherein step a) comprises pretreating the hair with a first primer composition which comprises the non-polymer composition in which the surfactant is at least one anionic surfactant and is substantially free of cationic polymers and cationic surfactants, and step b) is carried out and further comprises pretreating the hair with a second primer composition which comprises the non-polymer composition in which the surfactant is a cationic surfactant.

6. The method according to claim 1 , wherein the cationic polymer is selected from the group consisting of linear polyethyleneimine, branched polyethyleneimine, polyallylamine hydrochloride, polydiallyldimethylammonium chloride, copolymers thereof and mixtures thereof.

7. The method according to claim 1 , wherein the anionic polymer is selected from the group consisting of polystyrene sulfonate salts, λ-Carrageenan, Dextran sulfate salts, polyacrylic acid, poly(methacrylic acid) salts, alginic acid salts, carboxymethylcellulose salts, copolymers thereof and mixtures thereof.