Bubble coalescence in pure liquids and in surfactant solutions

•Bubble coalescence with pure liquids and salt solutions was recently clarified.•No complete model is available yet for surfactant solutions.•The critical applied pressure for film rupture decreases with increasing film size.•The critical pressure notion applies to foam films, emulsion films and even asymmetric films.

The mechanisms for bubble coalescence in the absence of surfactants were clarified, including for salt solutions. No complete model is available yet for surfactant solutions. The notion of critical applied pressure for film rupture, decreasing with increasing film size, appears applicable to foam films, emulsion films and even asymmetric films.

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