Dynamic Processes in Soap Films

Some relations between the two main types of thin liquid films, the water-in-air "soap" films and the invert oil-in-water "lipid" films, are outlined, and several dynamic aspects of film behavior are illustrated and briefly reviewed with reference to more complete treatments. These dynamic processes are important in both types of films, but are easier to study in soap films. The topics include the difference between rigid and mobile films and their interconversion; the origin and measurement of film elasticity; the effect of rate of formation upon film thickness, and the evidence against the existence of thick rigid water layers at the surface; and the kinetics of drainage and the role played in it by viscous flow, marginal regeneration, and intermolecular forces.