Plaster of Paris Sand Casting

Discuss some history of molding. Include thoughts on fossils.(the imprints of leaves, footprints, shells) Explain that the plaster is not for very detailed designs. The students need to make drawings of their ideas for the casting. Suggestions are simple designs like crosses, fish, and stars.

I have play sand in large tubs with lids. The sand needs to be three or four inches deep in the tub. Pour in enough water to make the sand moldable. (like at the beach when making sand castles.) Have the students manipulate the sand into the shape they desire. If they are creating something like a number or letter they will have to reverse the design or it will be backwards.

Set the stones or beads or glass shards slightly into the sand. Remember to turn these beads, etc., down as they will also be opposite. Mix up the plaster of paris per directions. It is a 2 to 1 recipe, that is two plaster, one water. Stir with spoon, then use your hands to make sure all the clumps are disolved. Pour into the sand mold, try not to overfill. Let stand a few minutes, then put in a hanger. Leave alone for at least 4 hours depending on the size. Overnight is better.

Gently pull casting out of sand. Let it dry completely then gently brush off excess sand with a paint brush. Coat casting with a polyeurathane. (This gives the work a shine and sets the sand.)