Shampoo and Conditioner Science 100 Deposition of Particles on Hair to Confer Styling Benefits Whereas conditioning shampoos are formulated to reduce hair inter-fiber friction, some consumers need an increase in friction in order to achieve styling benefits. Factors that influence hair body and fullness include hair diameter, hair fiber-to-fiber interactions, natural configuration (kinky, straight, wavy), bending stiffness, hair density, and hair length. Increases in friction can be achieved by depositing particles such as titanium dioxide, clay, pearlescent mica, or silica on the hair surface. Particles can be deposited for more purposes than merely increasing inter-fiber friction, e.g., for conferring color, for slip (spherical particles are best for this) and for conditioning (hollow silica, hollow polymer particles). Hollow particles can be included in shampoo to increase hair volume.69,70 Deposited hollow particles that can increase fiber-fiber interaction include complexes of gas-encapsulated microspheres such as silica modified ethylene/methacrylate copolymer microspheres and talc- modified ethylene/methacrylate copolymer microspheres polyesters and inorganic hollow particles. It has already been noted that cationic guar enhances the deposition of conditioning agents. Thus, in like manner, this macromolecule enhances the deposition of particles on hair.71 Silicones and particulates can be deposited simultaneously. Thus, enhanced deposition of particulate actives, such as zinc pyrithione (shown on cadaver skin treated in a Franz diffusion cell), has been reported72 from shampoos comprising a water-soluble silicone (such as silicone quaternium-13, cetyltriethylammonium dimethicone copolyol phthalate, or stearalkonium dimethicone copolyol phthalate), a cationic conditioning agent (such as acrylamidopropyltrimonium chloride/acrylamide copolymer, or guar hydroxypropyltrimonium chloride), a cleansing detergent, and suspending agents (such as carbomer, hydroxyethylcellulose, and PVM/MA decadiene cross-polymer ) to insure homogeneous distribution of the insoluble active. Hydrophobic modification of cationic hydroxyethylcellulose is claimed to endow better efficacy. Thus, polyquaternium-24,