Saturday Science: Eggshell Sidewalk Chalk
Did you make omelettes, scrambled eggs or maybe a frittata for your family’s Saturday morning breakfast? Don’t throw away those eggshells! Use them for this week’s Saturday Science experiment, courtesy of Almost Unschoolers.
- A clean rock
- Hot water
- Food coloring
- Mixing bowl
- Mixing spoon
- Paper towels (or paper napkins)
- Wash out the eggshells and allow them to dry completely.
- Use a clean rock (or mortar and pestle) to smash the eggshells into a fine powder.
- For each piece of chalk, add one spoonful of eggshell powder, one teaspoon hot water, one teaspoon flour and a few drops of food coloring to your mixing bowl and mix ingredients together.
- Pour chalk paste onto a paper towel and roll it so that it is the shape of a long piece of chalk.
- Let dry for at least three days.
- Peel the napkin or paper towel off of your chalk.
- Take your chalk outside and start drawing! (Note: To prevent scratches, do not use this chalk on a chalkboard.)
Did your eggshell sidewalk chalk allow you to draw beautiful sidewalk pictures just like the chalk that can be bought in a store?
Store-bought sidewalk chalk is made from a combination of calcium carbonate, gypsum, silica, phosphorus, iron, alumina, phosphorus, sulfur, manganese, copper, titanium, sodium oxide, fluorine, strontium and arsenic. Its main ingredient, however, is calcium carbonate – a form of limestone. 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.