Abstract: To make a molded article from expandable synthetic resin particles, especially polystyrene particles, the cooling of the individual mold wall portions is effected exclusively by evaporating condensate obtained from stream, advantageously condensate which accumulates in stream compartments on the exterior or back sides of the mold walls which was fed in for heating of the mold wall portions and fusing the synthetic resin particles. This evaporation of condensate is effected on the back surfaces of the mold wall portions facing the steam compartments because of a low pressure or suction produced in the steam compartments. The condensate is fed in hot at or just below the boiling temperature of the condensate. Surfaces of the mold wall portions facing the steam compartment have increased surface area by reason of spherical surface-area increasing elements which form constricted passages between a plurality of interior reservoir cavities and the outside steam compartment.