Patent No. US 7,390,478 B2. Sebastian International has patented a method of treating hair to increase its thickness. The method entails pre-treating the hair by applying a high pH composition to the hair to lift cuticle layers of the hair and then applying a low pH composition containing a thickening agent to the pre-treated hair to make the thickening agent substantive to the hair and closing the cuticles to seal the thickening agent to the hair. The high pH composition is comprised, based on the weight of the high pH composition, of conditioning agent, solubilizer for the conditioning agent, rheology control agent, one or more preservatives, fragrance, water and a basic pH adjuster to bring the pH of the composition to 9-9.50. The conditioning agent is PEG-12 dimethicone; the solubilizer for the conditioning agent is polysorbate 20; the rheology control agent is PEG-90M; the pH adjuster is aminomethyl propanol; and the preservatives are a combination of phenoxyethanol, methylparaben, ethylparaben, butylparaben, isobutylparaben and propylparaben.