Calcium carbonate (CaCO3) is the chemical that lets us draw on the sidewalk with a piece of chalk.

Do you know what else contains calcium carbonate? Eggshells! This makes them a great alternative to store-bought chalk.  Have fun making homemade chalks and let your kids get creative!

Materials

  • 4-5 Eggshells
  • Hot water
  • Flour
  • Food colouring
  • Mixing bowl
  • Mixing spoon
  • Paper towels (or paper napkins)

Process

  1. Wash and dry the eggshells. If you can, remove the thin membrane from inside the egg shells.
  2. Crush the egg shells as finely as you can. A food processor works, but you’ll get the finest powder if you use a mortar and pestle or an old coffee grinder.
  3. Mix one teaspoon of flour and one teaspoon of hot water in a small bowl. Mix it until it’s a paste.
  4. Add one tablespoon of egg shell powder to your paste. Add a few drops of egg colouring.
  5. Mix until everything is combined. If you can’t press the mixture into a log shape, add a bit more water.
  6. Shape the eggshell mixture into a log shape.
  7. Use one of these two methods to dry your chalk:
  • Wrap the log into a piece of paper towel and let it sit 3–5 days. If the chalk starts to crumble when you write with it, let the chalk sit for another day or two.
  • Alternatively, place the chalk on a small baking pan lined with parchment paper. Bake the chalk on a very low setting, 65°C, for 90 minutes. Let the chalk sit for 24 hours to finish drying.

Take your chalk outside and start drawing!

Share your colourful creations with us, tag Farmer Jacks on Instagram!