Polystyrene beads, which contain a blowing agent (usually pentane), are heated with steam. This causes the beads to expand up to 40 times their original size.
The expanded beads are then aged to allow the pentane gas to escape and air to replace it, stabilizing the beads.
The expanded and aged beads are placed into a mold. The mold is then heated with steam, causing the beads to expand further and fuse together, forming a solid, rigid foam product in the shape of the mold.
The mold is cooled, and the finished EPS foam product is ejected.
