Production of foam products requires that the raw material be conditioned prior to the final "tooled" moulding process. The raw material has a spherical shape and looks like sugar.

The conversion process has three stages:

Pre-Expansion

The tiny spherical polystyrene beads are expanded to about 40 times their original size using a small quantity of pentane (typically 5% by weight) as a blowing agent. This process involves the heating of beads, using a flow of steam, which causes the blowing agent to boil and thus a honeycomb of closed cells is formed.

Maturing

As the material cools the pentane liquefies and a partial vacuum is formed inside the bead. The beads are returned to a holding tank for approximately twelve hours to allow the pressure differential to equalize, giving a stabilised granule.

Final Forming

In this final stage the pre-expanded stabilized beads are reheated with steam and injected into a mould. The final expansion takes place and the beads coalesce to give a shaped moulding. This can also be used to form large blocks which can be sectioned to the required shape as panels, boards, cylinders etc. In this final form the EPS is made up of 98% air.