  While coalescence is ultimately the most drastic destabilization process in
foams, its underlying processes are still unclear. To better understand them,
we track individual coalescence events in two-dimensional foams at controlled
capillary pressure. We obtain statistical information revealing the influence
of the different parameters which have been previously proposed to explain
coalescence. Our main conclusion is that coalescence probability is simply
proportional to the area of the thin film separating two bubbles, suggesting
that coalescence is mostly stochastic.
