a method and apparatus for forming foam articles is described . thermoplastic resin beads containing a blowing agent are continually agitated in a heated pre - expansion chamber to a temperature near the fusion point of the beads and above the boiling point of the blowing agent at substantially atmospheric pressure . the beads soften and expand substantially in volume . a dry gaseous medium may be swept over the beads to remove moisture and any blowing agent which has escaped . thereafter , the chamber is evacuated . evacuation continues until a predetermined amount of blowing agent is removed from the beads . as a preferred embodiment of the invention , steam may be injected into the chamber prior to evacuation . this serves to further expand the beads , and facilitates the removal of the blowing agent . this embodiment also provides a means of manufacturing particularly stable low - density foam . the expanded beads , after they are restored to atmospheric pressure , are discharged to a storage facility and maintained at an elevated temperature for immediate use in a molding apparatus . the expanded hot beads may be fed directly by air injection conveyors to mold cavities and molded into the desired articles .