ABSTRACT
This chapter presents a complete review of the various mechanisms proposed for the action of antifoams over the past half-century. Theories which require the antifoam to be surface active associate antifoam behavior with an effect on surface tension in the foam films which leads to film rupture. The chapter outlines the main processes which are believed to contribute to the stability of foam films in the absence of antifoam. It examines the relationship between antifoam effects and surface activity of the antifoam. The chapter is concerned with inert hydrophobic particles and capillary theories of antifoam action in aqueous solutions. It discusses the mode of action of the mixtures of hydrophobic particles and oils which form the basis of many of the commercial antifoam concoctions proposed for aqueous foams. Antifoam effects appear to require that the antifoam be undissolved in the foaming medium. Solubilization of the antifoam in micelles largely restores the foamability.
