HOW DOES A THIN WETTED FILM DRY UP

We study the thinning by evaporation of completely wetted water films on clean mica surfaces in a pure water vapor environment. In the thick ness range from 100 to approximately 1000 angstrom the thinning is uns table to nucleation of dry patches, and the spreading of these patches invokes a ''de-wetting'' of the substrate. The initial process is des cribed by a simple nucleation theory. A number of hydrodynamic effects and instabilities are also observed at the boundary of the film.