Shampoo and Conditioner Science 102 but these demulsifiers tend also be defoamers that compromise the lather of shampoos. Neutralized polyacrylate can be added as a non- emulsifying foam stabilizer to yield phase-separated compositions that resist the production difficulties to make phase-separated shampoos that form temporary emulsions upon shaking and foam during use.76 A two-phase shampoo system can also be formed by mixing polar lipophilic shampoo components with non-polar lotion constituents such as mineral oil.77 Under appropriate conditions, phase-separated systems can be prepared from polymer solutions or micellar surfactant solutions. If two distinct aqueous phases are desired in a composition, one must take into consideration the thermodynamics of coexisting phases and the driving force for such phase separation that comes directly from the chemical thermodynamics of the system. This is especially the case for systems that contain polymers or micelles because the configurational entropy is reduced as molecules are assembled into polymers or aggregated into micelles, and mixing can become unfavorable. If the free energy of mixing is insufficient to maintain uniform dispersion, spontaneous phase separation will occur. Phase separation becomes more likely as the micellar aggregates or polymers get bigger. The addition of salts to ionic surfactant micellar systems causes a reduction in the surfactant intra-micellar head- group interaction, and often an increase in hydrophobic interaction. This can cause a pronounced increase in micelle size and consequent phase separation into a surfactant-rich phase and a surfactant-poor phase. This approach has been adopted by adding mineral salt to induce two distinct layers,78 and by adding the detergent builder, sodium hexametaphosphate, to cause phase separation. In this case, a thickener is required and the system comprises a surfactant, a thickener, a polyalkylene glycol, and a non-chelating mineral salt. The system spontaneously separates into two layers. A multiphase composition comprising surfactant, betaines, co-surfactant (such as an alkyl ether carboxylate, an acylglutamate or an acylisethionate), and an appropriate concentration of salt