1 cup Plaster of Paris (do not pack)
About 1/3 to 1/2 cup cool water
Liquid tempera paints, any color
Pour plaster into a disposable container (i.e. margarine container or large paper cup.) Stir in most of the water. Add 2-3 tablespoons of liquid tempera, mixing well, especially at the bottom. Add a little more water as the mixture thickens. Stir well and pour into containers.
Three-ounce paper cups work well. Peel paper off when the chalk is dry.