Disclosed is an apparatus for evaporation of a vacuum evaporatable material onto a substrate, said apparatus comprising (a) a walled container for the vacuum evaporatable material having a plurality of apertures in a surface thereof, said apertures being configured so that the vacuum evaporatable material is uniformly deposited onto the substrate; and (b) a source of heat sufficient to effect evaporation of the vacuum evaporatable material from the container through the apertures onto the substrate, wherein the surface of the container having the plurality of apertures therein is maintained at a temperature equal to or greater than the temperature of the vacuum evaporatable material.