ABSTRACT
The Marangoni effect can be explained schematically in Fig. 17, which shows that if the solution is too dilute to stabilize the foam film, the differential tension will be relatively small and little foaming will occur. In the case of the solution being too concentrated, the differential tension relaxes too rapidly because of the supply of surfactant, which diffuses to the surface. This causes the restoring force to have time to contact the disturbing forces, producing a dangerously thinner film and poor foaming. The maximum foam volume can be observed at the intermediate surfactant concentration range at which the Marangoni effect enhances foam stability.
