This research project is concerned with the drainage and stability of thin films which could be associated with unstable foams. The role of surface viscosity in coalescence at liquid-gas interfaces is investigated using single bubbles. The premise of previous work is that the same factors influence both the coalescence of single bubbles or drops at phase interfaces and the displacement of an unstable foam in a porous medium. This research project focuses on studying, both theoretically and experimentally, the problem of the coalescence of single bubbles or drops. A more detailed theory that will include the effects of any electrostatic double-layer forces is currently being developed. Using these theories as a basis, a systematic experimental study of the effects of the surface viscosities upon the coalescence times of single bubbles at liquid-gas interfaces is initiated. This includes complementary measurements of the two surface viscosities.
