Drainage of vertical films

Foam films can be produced by pulling a frame out of a reservoir containing a surfactant solution. Three stages can be identified (1) initial formation of the film that is determined by the withdraw velocity (2) drainage of the film within the lamella, which causes thinning with time and (3) aging of the film, which may result in the formation of a metastable film. 

Assuming that the monolayer of the surfactant film at the boundaries of the film is rigid, film drainage may be described by the viscous flow of the liquid under gravity between two parallel plates, as given by the Poiseille s equation. 

Marginal retention In lamellae with mobile films 

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