How to Cast Plaster
Plaster casting is a fun way to make artwork. You can also make casts of your children's hands or feet when they are small for mementos of childhood when they are grown.
Things You Will Need
- 10 pounds of Plaster of Paris
- Petroleum jelly
- 2 large mixing bowls
- Large spoon
- Measuring cup
- Waxed paper
- Dishwashing liquid
- Craft glue
- Large measuring cup
- 13x9x2-inch baking pan
Protect the surface you are working on. Spread layers of newspaper on the work surface and on the floor underneath the work surface.
Make a plaster of Paris mold which will be used to create the plaster cast. To do this mix a pint of water in a large mixing bowl. Then add 8 cups of the plaster of Paris powder, 1 cup at a time, to the water. Only stir the mixture AFTER all 8 cups have been added. Stir until it is the consistency of oatmeal.
Lay a sheet of waxed paper in the bottom of the baking pan. Coat the object you will be making a plaster cast of with a generous layer of petroleum jelly. Place the item on the waxed paper. Make sure it's flat against the pan, and slowly add plaster of Paris until the item is completely covered.
Allow the first layer to dry for several minutes while the remaining plaster in the bowl thickens. If using a hand or foot, you must remain as still as possible. Cover the item with an additional layer of plaster. The plaster will take approximately 10 minutes to dry.
Remove item from the hardened plaster carefully and slowly, after the material has sufficiently cured. If some of the mold breaks off in this process, it can easily be glued back together.
Place the finished mold right side up in a baking pan full of water. The outside of the mold should come in contact with the water. While the mold is absorbing the water, fill a bowl with some dish soap and water.
Using a paintbrush, apply the soapy water to the inside of the mold to lubricate it for easy removal of the finished plaster cast.
Allow the mold to stay in the pan of water for about 5 minutes, or long enough to absorb enough water that the plaster mold is completely saturated. This will keep the mold from becoming too dry.
Spread a piece of waxed paper on a hard surface and lay the finished mold on the paper. Mix enough plaster of Paris to fill it about an inch past the rim of the mixing bowl.
Allow the fresh plaster to thicken for several minutes, then carefully pour it into the mold. It will need to harden for at least an hour before it can be removed from the mold.
Once the plaster is sufficiently hard, chisel away the mold using a hammer. Pliers may be used to remove plaster too. Do this slowly and carefully so as not to damage the finished piece. Any chips or cracks can be repaired with additional plaster. Allow any necessary repairs to dry before painting or decorating.
Paint the finished plaster cast with acrylic craft paint. Protect the finished piece, once the paint dries, with a coat of clear acrylic sealer. Allow the paint and sealer to dry completely, and add decorative trim of your choice.