Cut strips of plaster of Paris gauze prior to casting. Cover whatever is being cast in petroleum jelly so that it can be released easily. If you are casting a body part with hair, consider shaving the area that will be cast.
Fill a bucket with cold water to slow down the curing time of the plaster of Paris.
Create a plaster mixture for a molld: Using your hand, sift powdered plaster by the handful into the bucket of cold water; it will sink to the bottom. Continue doing this until the powder remains at the top of the water for at least 5 seconds before sinking.
Use your hand to quickly mix the the plaster on the bottom of the bucket with the cold water, breaking up all chunks with your fingers as you go. Your hand should have a thin coating of plaster stuck to it when you finish mixing.
Pour mixture into your mold immediately. Gently tap the bottom and sides of the mold, releasing air bubbles as you pour, and again after the plaster is completely poured.
Create a cast using plaster gauze by dipping the impregnated plaster gauze into cold water and gently run it between your fingers, making sure to activate and moisten all of the powder. Place strips on top of whatever you are casting.
Allow at least 10 minutes for plaster to harden before releasing a mold or removing a cast.