Thermodynamic and mechanical timescales involved in foam film rupture and liquid foam coalescence

Recent advances in the coalescence in liquid foams are reviewed, with a special focus on the multiscale structure of foams. Studies concerning the stability of isolated foam films, on the one hand, and the coalescence process in macroscopic foams, on the other hand, are not always in good agreement. This discrepancy reveals that two routes can induce coalescence in a foam. The first route is thermodynamic and shows that coalescence is governed by a stochastic rupture of foam films. The second route relies on a mechanically induced rupture of the films, due to the spontaneous evolution of foams. From a literature review, the evaluation of the different timescales involved in these mechanisms allows defining the limiting parameters of foam coalescence.