Product such as styrofoam cups and food containers, insulating blocks, and shaped packaging materials, are made by foam molding. The material is expandable polystyrene. Polystyrene beads are placed in a mold with a blowing agent and exposed to heat, usually by steam. As a result, the beads expand to as much as 50 times their original size and take the shape of the mold. The amount of expansion can be controlled by varying temperature and time.