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Linear and non-linear stability analysis of the interface between a thin vapor film and a layer of liquid in the presence of a steady heat flux from a metal surface heated to a high temperature, to the vapor film and then from vapor to the subcooled liquid is investigated. The temperature dependence of saturation pressure is taken into account. Boundary conditions on the vapor–liquid interface that generalizes the known correlations on the free surface of liquid in the gravity field are derived. The thermal processes on the phase boundary lead to the generation of weakly decaying periodic surface waves of low amplitude and may cause small length waves (ripple), which are not capillary ones. Thermal processes on the phase interface are capable to provide the stability of a film of lights vapor under a layer of heavy liquid in the gravity field. The explosive instability may arise in the non-linear stage due to a weak variation of the film thickness or superheating of liquids.

A study is performed into the processes of development of instability and collapse of a vapor film on a solid hemispherical surface. Optical-fiber sensors of pressure and vapor-film thickness are used in measurements; the process is videofilmed with subsequent computer processing of images. A physical model of the phenomenon is developed, which includes superheating and explosive boiling of water in recesses of wavy vapor film. The predictions are in qualitative agreement with the experimental results.