The stability of foams: Dependence of observation on the bubble size distribution

Abstract

The rate of foam collapse owing to interbubble gas diffusion is shown to be a sensitive function of the initial distribution of bubble sizes. Experimental evidence is presented to support these theoretical conclusions. The poor reproducibility of existing foam stability tests can be understood in terms of this sensitivity. The foam surface area decreases as a bilinear exponential function of time. One of the two characteristic time constants appears to be related to a gravity drainage mechanism while the second one is determined by the rates of gas diffusion between bubbles.