The effects of various physical parameters on the rupture of bubble films in two-phase foams were investigated in order to develop a better understanding of the behaviour of coarse particles in the froth phase of a novel flotation cell. This novel flotation technique is based on the fact that coarse particles, if they are selectively rendered hydrophobic by conditioning, would act as bubble film breakers. If the feed was introduced onto the surface of the froth, such particles would settle through the froth under gravity to be recovered as an underflow (concentrate) product, while the hydrophilic gangue would be supported by the bubble films and be recovered as a float (tailings) product. The efficiency of this technique-reverse froth flotation-depends on the interaction between various characteristics of particles and the froth. In order to simulate the experimentally observed trends, and hence investigate the various mechanisms qualitatively, a fundamental model of these interactions was developed. Various particle properties were taken into account, including surface properties, shape, size and density. To account for the changing nature of the froth at different positions in the cell, the model predicts the trajectory of a particle over discrete time events. This was accomplished by calculating bubble flow streamlines and modelling the bubble size, thickness of bubble films, air hold-up and bubble velocity at any point on the streamline. (C) 2002 Elsevier Science Ltd. All rights reserved.