Liquid drainage method, measuring foam

Liquid drainage has been shown to be a function of bulk liquid viscosity, surface viscosity, and the size of bubbles [16]. Also, recently, a CESIO working group mentioned a method using a turbine engine to stir diluted surfactant solutions (about 1 g/L) to measure foaming ability as well as foam stability. This method can be implemented to assess the efficiency of antifoam additives [17]. 

The overall rate constant, as opposed to the growth exponent, depends directly on such material parameters as the surface tension, the solubility and diffusion constant of gas molecules in the interstitial liquid, the film thickness and the liquid content (40, 41). Note that the dependence with the liquid fraction is not yet completely known (as measuring the coarsening of wet foams, at constant liquid fraction, is very difficult because of drainage). The studies of sound propagation into foams also turned out to be an indirect method to measure the coarsening (51). 

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