A process for treating a keratinous substrate involving: (a) providing at least a first composition having a continuous phase whose major ingredient has a solubility parameter corresponding to δ; (b) providing at least a second composition having a continuous phase whose major ingredient has a solubility parameter corresponding to δ′; and (c) combining (a) and (b) prior to, or during, their application onto the keratinous substrate, and wherein the difference between δ and δ′ is greater than 12, and wherein the major ingredient is chosen from a hydrophilic polar material, an organic non-polar material and an inorganic non-polar material.