EPS processing in a laboratory environment:

Pre-expanding:
100 grams of Polystyrene (eps) are boiled for 12 seconds in 750 mL of hot water in a 2 litre beaker while stirring. In order to stop the pre-foaming process 1 litre of cold water is rapidly poured into the beaker. Afterwards the water is rapidly poured through a sieve.

Drying:
The pre-foamed particles placed on a towel are allowed to air dry. In order to absorb air, the particles remain on the towel for 10 minutes.

Molding:
The mold used consists of two hemispherical parts that fit together forming an empty ball-shaped cavity. The two empty parts of the mold are filled with the pre-foamed eps beads. One part of the mold covered with a plastic plate is put on the other part. After the plastic plate is removed the two parts of the mold are bolt together. The eps-filled mold is placed for 10 minutes into a beaker containing boiling water.

Result:
After fusing (molding) the mold is cooled down by cold water. Afterwards the mold is opened and carefully the polystyrene ball is taken from the mold.

In a production setting (in our plants) this process is automated and carried out on very sophisticated equipment.  Having said that, this “table top molding” video does capture and fairly represent the basic process.

The video ! (no sound)

See a molding plant layout

See more about the molding process