- If you are using paper towel tubes, cut each tube in half, so it is roughly the length of a toilet paper roll tube.
- Cover one end of each tube with duct table to hold the contents within.
- Cut as many pieces of waxed paper as you have tubes, in pieces roughly 6 X 6 inches. Roll each piece of waxed paper loosely and insert it into a tube so as to effectively line the tubes. The top of the paper will be higher than the end of the tube. The waxed-paper liner will keep the chalk mixture from sticking to the cardboard and will eventually be peeled off.
- Pour the warm water into your bucket. Sprinkle the plaster of paris over the water and stir the mixture with a plastic spoon. The plaster of paris starts hardening within 20 to 30 minutes, so you need to work fast so that it does not harden too quickly.
- Next, pour the tempera paint into the plaster of paris mixture and stir untilit is mixed thoroughly. If you would like brighter colors, add more tempera paint to the mixture. We wanted to make a variety of colors of chalk, so we spooned about ½ to ¾ cup of plaster of paris into separate containers and mixed different tempera paint colors into each. We ended up making six different colors and next time might mix more.
- Stand each tube with the tape side down on a cookie sheet, flat baking dish, or box lid to make the project easier to transport to a drying location. Pour or spoon the colored plaster of paris mixture into the waxed paper-lined tubes. Lightly tap the sides of the tubes to release the air bubbles (so you do not have holes in your chalk). After you have poured all of one color into the tubes, start another color. When done, trim the excess wax paper so that it is closer to the cardboard tube.
It took three days for our chalk to dry. On the last day, we peeled off the duct tape so that the underside could dry. When the chalk is all dry, peel off the paper tubes and waxed paper. Your chalk is ready!