Shampoo and Conditioner Science 88 these structural features of a foam. The lamellae are stabilized by surfactants adsorbed at the air-water interface. Foams lose stability by two main mechanisms: draining of the liquid and puncture of the lamellae. The foam lamellae are the junctions between two foam bubble cells and the Plateau border is situated at the triple-cell junction. The Laplace pressure in the liquid components of the foam is inversely proportional to the curvature of the interface. The higher curvature of the Plateau border results in a lower pressure in that region and this causes the liquid in the foam to drain preferentially from the lamellae to the plateau borders. Based upon this reasoning, it can be understood that drainage can be hindered in two ways, namely by blockage of the lamellae or by blockage at the plateau border. About two decades ago, Des Goddard carefully measured the drainage from foam films, and he deduced that Polyquaternium-24 adsorbed across the lamellar interface and hindered the drainage of liquid from the foam. In addition, about thirty years ago Stig Friberg concluded that certain liquid crystals blocked the Plateau border region and thus delayed foam drainage and conferred longer-term stability on surfactant foams. In the case of cationic polymers, hindered drainage of the lamellar liquid could be caused by adsorption of the cationic entities at the lamellar Figure 13. Micrograph showing surfactant foam structure.