Above block drawings illustrate the process of manufacturing of Expanded polystyrene (EPS) from the Expandable polystyrene beads. Four stages can be seen in the figure-1. First the beads are fed to a vertical tank containing an agitator and a controlled steam input. The final material density is determined at this stage.

Density adjustment is carried out by by controlling the length of time the beads remain in the expander and or the pressure in the expander. Second, the expanded beads are stored in the open to air silos for few hours as a drying stage. During storage they are allowed to reach an ambient temperature. This process takes as long as three days or as short as few hours. This process is called the stabilization process, as condensation of the blowing agent and the surrounding water vapor occurs.

Later on, beads are poured in a mould of various sizes, depending on the manufacturer. Steam is injected from the walls of the mould through longitudinal tiny slots where fusion takes place. The basic EPS product is white, although it can be colored otherwise.