ABSTRACT
This chapter attempts a complete review of the various mechanisms proposed for the action of antifoams over the past seven or so decades. It is a feature of this subject that some proposed mechanisms, although plausible, have been speculative. Thus, unequivocal experimental evidence has sometimes been lacking. Indeed, the full theoretical implications of proposed mechanisms have also often not been fully developed. In the main, all of this derives from the extreme complexity of the relevant phenomena. As we have seen, foam is itself extremely complex, consisting of (usually) polydisperse gas bubbles separated by draining films. These films exhibit complicated hydrodynamics involving the distinct rheology of air-liquid surfaces and, for thin films, colloidal interaction forces. The nature of the foam film collapse processes that are intrinsic to foam are still imperfectly understood.
