4-5 eggshells,1 teaspoon flour,1 teaspoon very hot tap water,food coloring (optional)
Wash & dry eggshells. Put into bowl and grind into a powder. A mortar and pestle works fine for this. Discard any large pieces. Place flour and hot water in another bowl and add 1 tablespoon eggshell powder & mix until a paste forms. Add food coloring if desired. Shape & press mixture firmly into the shape of a chalk stick, and roll up tightly in a strip of paper towel. Allow to dry approximately 3 days until hard. Remove paper towel & you've got chalk! Eggshell chalk is for sidewalks only.