Polyurethane expanding foam is useful in art. We can usually make big sculptures with low weight.
Empanding foam can be sculpted after drying or casted by injecting it in a silicone mold.
Step 1: Polyurethane, That's It !
Sculpted or used brut !
Step 2: Polyurethane in Silicone Mold
Injection in a silicone mold is really easy. See it !