Plaster of Paris. You can get a large tub of this from most craft stores. You’ll need 1/2 cup per batch of chalk. Tempera paint. This type of paint washes away easily, which is convenient if you’ll be using your chalk on the sidewalk or on a chalkboard. Choose as many colors as you’d like. Wax paper. You’ll need this to line your chalk molds, so that the chalk doesn’t stick to them. Items to use as molds. You can use old toilet paper tubes, paper towel tubes, ice cube trays (as long as you don’t use them again to make ice), or any other type of tube or carton. Masking tape. You’ll need this to cover the bottom of the tube molds to keep the chalk mixture inside.
Eggshells. If you are lucky enough to have an egg-laying hen, you might have a store of eggshells just waiting to be used. If not, find a way to gather as many eggshells as possible. If you start in advance you can ask your friends and neighbors to save them up for you. Flour. This thickens the mixture and fills out the chalk. Food coloring. Either the liquid or gel kind will work. Molds. Use old toilet paper rolls, an ice cube tray, or any other type of mold of your choice. Wax paper. You’ll need this to line the molds. Masking tape.
For a fun variation, try filling the molds halfway with one color, then filling up the other half with a second color. Make marbled chalk by filling the molds with two or more colors, then using a wooden skewer to poke through the paint layers and create swirls.
