Foam drainage: a film contribution?

We have measured the steady drainage of foams of various surfactants, varying the size of the parietal plateau borders from 0.24 to 2.4 mm. We report an evolution of the power laws of drainage with the bubble size, which cannot be explained by the most recent developments of the drainage theory. We believe that one reason for the disagreement between the existing theory and our data is the passage of liquid through the films, from nodes to nodes. Film thickness measurements in situ show that the films are swollen, up to 2 microm and more. Films, usually neglected, may then have an important contribution to drainage by increasing noticeably the volume of the regions where the liquid flows.