The raw plastic polymers have no shape and must be moulded by a number of moulding techniques. During the moulding phase dyes and fillers are added to give the plastic colour and varying properties.

The animation on the left is of a moulding process called "Blow Moulding". Blow moulding is used for the production of plastic bottles.

During this process plastic granules are heated and extruded into a fine long tube. This hot and flexible tube is placed in the mould. The mould closes sealing off one end while the other end has hot air blown into it. The plastic is forced against the sides of the mould and takes the shape of the mould.

Blow moulding uses a class of plastic called a thermoplastic. Such plastics soften when heated and harden when cooled.