2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/141166We present here a simple model describing coexistence of solid and vapour phases. The two phases are separated by an interface. We show that when the concentration of supersaturated vapour reaches the dew-point, the droplet of solid is created spontaneously on the interface, adding to it a monolayer of a visible size.Mathematical Physics82B20text