Plaster bandages are one of the most useful tools when it comes to the art of mold making and casting. The are especially useful in creating shell or mother molds. These are the rigid shells which are laid over mold making rubbers that provide the needed support for casting once the mold is removed from the model.
The most efficient technique in using plaster bandages is to first roll out about six to eight inches of a bandage; roll it back on itself, then roll it back once again. That way you will have three layers of bandage in a collapsed "S: shape. Now cut it apart and continue creating 3-ply bandages. Stack them in a pile that is "X" shaped so they will be easy to pick up when you are ready to apply.
A face needs one bandage roll, whereas a front torso needs about eight or nine. Have two bowls of warm water at the ready. Holding a bandage end in each hand, dip the bandage in the water until saturated. As the water in one bowl becomes milky use the second bowl, as continuing to use the milky water will cause the bandages to delaminate later on when you least expect it.
Lift out and gently squeeze out excess water. Apply over the rubber or alginate surface smoothing out so there are no air pockets. Repeat, applying the next bandage, over lapping the first by a third until the rubber surface is covered.
Now take a whetted-out bandage, hold it in one hand and fold length wise in half. Then fold again in quarters. This will be a reinforcement bandage which you will place all around the edge of your plaster bandage shell to reinforce the edges.
In addition, plaster bandages may be applied on the body to create a mold in itself. It will provide less detail than an alginate or silicone mold, but it make for an easier application. It will provide a wondeful "form" mold and is often the choice for belly casting (pregnancy molds).