Use plaster-casting molds by coating them with a mild soap, placing them on a level surface and pouring the mixed plaster into the mold. Once the cast is cool, remove it from the mold.
Before beginning to mix the plaster, ensure everything is ready for pouring. Proper molding requires working quickly after the mixing the plaster and does not leave time for preparing molds.
The plaster should be dry and free of lumps before mixing. If you have stored it in damp conditions, the best option is to discard it and purchase fresh materials. Weigh both the water and plaster before mixing. The ratio should be approximately 74 to 82 parts water for every 100 parts plaster. Avoid dumping the plaster directly into the water; instead, sift it onto the surface and give it two to three minutes to soak before mixing. Then mix and pour the materials.
Avoid getting plaster into drains because it can form a hard plug. Line a large bucket with a garbage bag, and fill it with water for cleanup after pouring plaster. Use this bucket for cleaning your hands and molds. Allow the solid materials to settle, and pour off the water. Discard the garbage bag containing the excess plaster.