  By introducing finite size surface and interfacial excess quantities,
interactions between interfaces are shown to modify the usual surface
premelting phenomenon. It is the case of surface melting of a thin solid film s
deposited on a planar solid substrate S. More precisely to the usual wetting
condition of the solid s by its own melt l, necessary for premelting (wetting
factor F<0), is adjoined a new quantity G describing the interactions of the
l/s interface with the s/S interface. When G>0 this interface attraction boosts
the premelting so that a two stage boosted surface premelting is foreseen: a
continuous premelting, up to roughly half the deposited film, is followed by an
abrupt first order premelting. When G<0 these interfaces repell each other so
that premelting is refrained and the film remains partly solid above the bulk
melting point (overheating) what is called astride melting. Elastic stress
modifies both types of melting curves. Bulk and surface stresses have to be
distinguished.
