Shaping keratin fibres using 2-hydroxypropane-1,2,3-tricarboxylic acid and/or 1,2,3,4-butanetetracarboxylic acid

A method for straightening curly hair comprising:

• (a) providing in a package a solid composition, wherein the solid composition comprises:
• hydrophobically modified alkali soluble acrylic polymer emulsion;
• an active agent, wherein the active agent is a mixture of 2-hydroxypropane-1,2,3-tricarboxylic acid and 1,2,3,4-butanetetracarboxylic acid;
• a photocatalyst which is a mixture of 8-hydroxyquinoline and 8-quinolinol-1-oxide;
• and then mixing the solid composition with a cosmetically acceptable carrier to form a crosslinking composition comprising from about 10% to about 90% water;
• wherein the crosslinking composition has a viscosity of from about 1 mPa·s to about 80,000 mPa·s;
• and then
• (b) applying the crosslinking composition comprising from about 5% by weight of active agent, 100 ppm 8-hydroxyquinoline and 100 ppm 8-quinolinol-1-oxide photocatalyst to curly hair, mechanically straightening the hair with a hair straightening iron at a temperature of about 250° F. and exposing the composition to electromagnetic radiation having a wavelength of 380 nm;
• wherein the method does not comprise a rinsing step between step (a) and step (b) and wherein the crosslinking composition prepared by the mixing stage of step (a) has not been exposed to said radiation for a period of 10 minutes or more and wherein it is not a requirement that the solid composition of step (a) has not been exposed to said radiation;
• and wherein 0.25 g of said crosslinking composition per gram of hair is used in the method.