This is the cheapest and easiest method of preparing a mold for lost wax casting. All you need is your wax sculptures with sprues, plaster of paris, water and containers.
Step 1: Make a Plaster Mixture
Use two parts plaster powder to one part water. Most plaster packaging instructions say to mix water into plaster. On the contrary introducing plaster powder to water will minimize the amount of bubbles. So start with water and gradually add plaster. Note- plaster powder shrinks as it soaks, you'll use a lot more then you think so be supplied with a big bag before you start.