Shampoo and Conditioner Science 104 this context, Guth claimed a composition that was low-irritating to skin and eyes but synergistic in foaming by combining zwitterionic surfactants-fatty acid complexes with sulfosuccinates,86 and Pratley reported synergistic foaming and mildness from compositions with combinations of specific long-chain surfactants with specific short-chain surfactants and these included fatty acids and alkylsulfosuccinnates.87 Amine-oxide copolymers have also been claimed as suds-enhancers.88 Concentrated Cleansing Compositions Most personal care products are based on aqueous compositions but concentrated cleansing/personal care compositions offer the benefits of lower transportation costs, less packaging, and convenience for air travelers. If these products are solid, they must possess sufficient strength to resist the forces of extrusion during manufacture, and also shipping and handling, but should disperse rapidly in water during use. Porous solid articles that are strengthened by hydrophilic polymers such as poly(vinyl alcohol) or hydroxylpropylmethylcellulose have been shown to exhibit the desired properties.89 Control of interconnectivity of the porous network is vital to this application and this is described by a star volume, a structure model index or a percent open cell content. Conditioners Conditioning of damaged hair is commonly achieved by treatment with aqueous formulations that contain fatty alcohols, cationic surfactants, and (optionally) silicones. These components are considered to adsorb in a hydrophilic head-down, hydrophobic tail-up conformation that confers hydrophobicity on the damaged hydrophilic hair surface. The role of a conditioner is to confer sleek lubricity and gloss on the hair. Conditioners are usually based upon cationic surfactants, and they most often are in the form of emulsions of multi-lamellar vesicles. Conditioners comprise a primary cationic surfactant, a co-surfactant, and dissolved salt. Conventional conditioner formulations are based upon lamellar