Named after a large gypsum deposit in Paris, plaster of Paris is a powdery white substance that hardens when mixed with water and left to dry. It's used by law enforcement agencies to transfer tire tracks and footprints, and it's also handy for making crafts. Even doctors use the substance, smoothing it over bandages on broken limbs to immobilise them until they heal. With a few supplies, you can use plaster of Paris for many applications.
Measure out the amount of plaster of Paris needed to make a mould. The general use for most brands of plaster of Paris is 1 part water to 2 parts plaster, with a yield of approximately 1 1/2 cups of the finished product.
Pour water into the mould to the level you want the plaster, then measure it out in cups. For instance, if you want to make a mould of your handprint in a pie plate, you would pour water in to the depth you want. If you used 4 1/2 cups of water, you would then need to use 6 cups of plaster of Paris and 3 cups of water.
Measure out the dry plaster into a plastic bowl and make a well in the middle. Pour in the water all at once, and stir until the mixture is smooth.
Pour the liquid plaster into your mould slowly, starting with the lowest areas and filling in all the spaces. Use all the plaster you prepare, as it doesn't store well.
Allow your plaster of Paris mould to sit undisturbed until it hardens. Carefully loosen the edges, and allow the plaster to fall out. Make sure you catch it.
Use prepared plaster bandages to wrap around fully inflated balloons to make easy pinatas. Dip the pre-rolled bandages in warm water, allowing them to soften before wringing gently and unrolling onto the surface of the balloon. Use a single layer, and allow it to dry completely before popping and removing the balloon from the top.
Make free castings by pouring mixed plaster into animal tracks or other indentions and letting it harden.
Fashion small bits of jewellery by filling tiny plastic moulds with plaster and painting the hardened objects to use on children's bracelets and chains.
Wash your hands after using plaster. Since plaster of Paris absorbs water, it will dry your skin out quickly.