Polyurethane Spray foam can be used as a sculpting medium to create just about anything. Any size.
As shown in the images below a base is made out of wood, steel, chicken wire, foam strips, foil. Spray polyurethane spray foam is then sprayed to the base building it up where you will be shaping your prop, and then allow to fully cure.
Polyurethane spray foam can be, carved, sanded and grinded. As seen in these images of the large bee, the polyurethane spray foam has been covered with polyester resins. This allows for weather protection and easily creates surface textures in many shapes and colours.
Polyurethane spray foam is also used to create a cave roof effect.