6 Eggshells
1 ts Very hot water from the tap
1 ts Flour
The eggshells should be washed so they don't have any egg left in them. Dry them well. Take them outside and grind them with a rock on the sidewalk or other concrete surface. Make sure the rock you're using for grinding is clean so you don't get dirt ground in with the eggshells. Grind the eggshells into a fine powder. You'll need one soupspoonful of this powder to make a stick of chalk.
When you're absolutely sick of grinding and have enough powder, pick out any little bits of eggshell that are still not ground up and throw them away. Scoop the eggshell powder into a paper towel and bring it into the house for the next part.
Measure the flour and the hot water into a small dish. Stir them together to make a paste. Put the soupspoonful of eggshell powder into the paste and mix well. It may help to mash it with the back of the spoon.
Shape this mixture into a chalk stick. Then roll it up in a strip of paper towel. Let it dry. Drying takes about three days, so put it in a safe place and get on with your life. After three days it's ready to use. Just peel the paper off one end and you're ready for some sidewalk art.
(This chalk is for the sidewalks only, not for chalkboards.)