Characterization of foam stability by the use of foam models 1. Models and derived lifetimes

In practice, foam stability is tested by different methods which measure different quantities, the numerical values of which are sometimes without exact physical sense or even contradictory. In order to understand discrepancies and to obtain reliable data for foam stability, several foam models of differing complexity have been elaborated which provide quantities of a similar nature, i.e. bubble lifetimes. The models correspond to single bubbles, to the one-bubble-thick foam in its steady state and during decay, and to thicker, but not too thick, foams.