Wash the eggshells well, so they don’t have any egg left in them.

Dry them and grind them into a fine powder in a food processor. You will need one tablespoonful of this powder to make a stick of chalk.

Measure the powder. When you have enough powder to make a stick of chalk, sift or pick out any little bits of eggshell that are still not grounded and throw them away.

Stir the flour and hot water together in a small dish to make a paste.

Put the tablespoonful of eggshell powder into the paste and mix well.

It may help to mash it with the back of the spoon. Add a few drops of food coloring.

Shape this mixture into a small log like the chalk sticks you buy.

Then roll it up in a strip of paper towel and set aside to dry for one to three days. Then just peel the paper off one end and you are ready for some sidewalk art.

For really big sticks of chalk, try making 3 times this recipe, and stuff the mixture into an empty toilet paper tube. When it is dry, you can peel away the cardboard as you use it.