Abstract: A mold for use in heat expanding prefoamed polystyrene beads to form a part of a predetermined shape is disclosed. The mold comprises a cavity defined by separable mold wall portions. Each mold wall portion has on its exterior a chamber into which a heating medium is introduced to heat the mold walls and also into which cooling medium is introduced to cool the walls. A plurality of nozzles are provided in the mold walls and a corresponding plurality of tubes interconnect the nozzles to a manifold located in the corresponding chamber. A pressurized heating medium is introduced to the manifold whereby the heating medium is injected into the cavity to expand prefoamed polystyrene beads in the cavity. A device is provided on the manifold for the selective removal of condensate from the manifold. The mold construction provides for an economical, readily manufactured unit.