How to Make Eggshell Chalk
Next time you have scrambled eggs, an omelette or do some baking, save the eggshells and use this activity to turn them into homemade pavement chalk!
What you need:
6 clean eggshells
Flour
Hot water
Food colouring
Why buy chalk when you can make your own with just 4 ingredients?
What to do…
Make sure to clean your eggshells thoroughly and try to gently remove the membrane inside the shell.
Once completely dry, grind the eggshells into a fine powder using a food processor or mortar and pestle.
Stir 1 teaspoon of flour and 2 teaspoons of hot water in a small bowl to form a paste.
Add 1 tablespoon of crushed eggshells and 2-4 drops of food colouring to the eggshell paste.
Mix to combine.
We used the back of a spoon and spent some time mashing the paste to ensure it was completely combined.Use your hands to roll the paste into a "chalk stick" shape.
Wrap the chalk in a paper towel and leave in the sun until dry (approx. 2-3 days) OR bake at 150C for 90 minutes and leave for 1 day to dry.
The resulting chalk is ideal for creating pavement artworks or leaving positive messages.
The science behind your chalk…
The main ingredient in store-bought chalk is calcium carbonate, which is a form of limestone. Calcium carbonate (CaCO3) is the chemical that lets us draw on the pavement with a piece of chalk.
Eggshells also contain calcium carbonate which is why you can turn them into chalk.
As an experiment, try drawing on the pavement using both store-bought and homemade chalk. Which worked best? Do you have a hypothesis as to why?
Did you give it a go?
Send us a photo of your chalk and what you drew and you might find your creation featured in a future issue of Upstart magazine… AND win a prize!