(1) Pre-expander
Upon contact with steam the pre-foaming agent found within the polystyrene beads starts to boil and the beads are expanded to between 40 to 50 times their original volume.
(2) Conditioning
After expansion the beads undergo a maturing period in order to reach an equilibrium temperature and pressure.
(3) Moulding
The beads are placed within a mould and again reheated with steam. The pre-foamed beads expand further, completely fill the mould cavity and fuse together.