SIDEWALK CHALK
To make 1 stick: 1/3 - 1/2 c. water Tempera paint (powdered is best) Mix in either a bowl or a zip-lock bag the plaster of Paris and powdered paint or the plaster of Paris and 1/3 cup water plus a little liquid paint. Add more water if necessary, until mixture is the consistency of pancake batter. As you mix the batter it will start to thicken and get hot. Pour into a zip-lock bag and push it to the bottom. Roll the bag up and place in a toilet paper roll to form a round stick. Let set for 24 to 48 hours, unroll bag and open up so that air can get to it. Let set another 24 hours or so (the harder it is, the longer it'll last).