Water
Teaspoon
Plastic ice cube tray
Measuring cup
Food coloring
Mild powdered white laundry soap

Fill half of a measuring cup with laundry soap. Add 40 drops of food coloring. Add water by the teaspoonfuls. Stir until you have a thick soapy paste, all one color. Pack into ice cube tray. Set tray in a dry sunny place for 1 to 2 days. Crayons will harden and pop right out.