Instant Molds Plaster of Paris Bandage Tips Tutorial. Plaster of Paris bandages are one of the most useful tools when it comes to the art of mask making, mold making and casting. Plaster bandages are especially useful in creating shell molds or mother molds. This is the rigid outer layer of a mold which is laid over alginate and silicone rubbers that provides the support for casting once the mold is removed from the model.