The profile of the draining film beneath a rigid sphere approaching a deformable fluid-liquid interface has been studied theoretically. A partial differential equation governing the variation in shape of the film with time has been obtained by considering the effect of the pressure gradient, due to viscous flow and gravity, on the deformable fluid-liquid interface. The variation of symmetrical experimental profiles usually lies between that predicted assuming the interface is immobile or fully mobile, and corresponds to an increase in mobility of the interface with time. The differential equation is independent of whether the sphere is approaching the interface from above or below and this has been confirmed experimentally. © 1969.
