Manufacture of polymeric foam

In a process for the production of slabstock polymeric foam product comprising supplying a reactant mixture for forming the slabstock polymeric foam product to a vessel having an overflow outlet, allowing the reactant mixture to begin reacting in said vessel, passing the reacting mixture over said overflow outlet onto a downwardly-inclined surface and into a channel-shaped conveyor, the reacting mixture forming a foam product having an upper skin with a generally flat top surface, the improvement including the step of applying upper and lower sheets to an upper surface of the reacting mixture adjacent said overflow outlet so as to reduce a thickness of the upper skin formed in the foam product, said lower sheet being in contact with the upper surface of the reacting mixture and composed of a flaccid material for conforming to said upper surface, said upper sheet being composed of a relatively stiff foil material, said upper and lower sheets being separate and freely movable relative to one another when applied to the upper surface of the reacting mixture.