3. Methods for studying foams

It is clear from the preceding paragraphs that a large number of phenomena are involved in the formation and maturation of a foam, often in competition with one another. Some methods are designed to study only one of these phenomena, in particular those which analyze the behavior of an isolated thin film, and it is not always possible to extract reliable information on the corresponding behavior of the foam. In what follows, we limit ourselves to methods for the global study of foam, which enable us to estimate the abundance of foam produced, or foamability, on the one hand, and its persistence, or stability, on the other.