Toothpaste vs Cola

What's this Science Bite about?

In this egg-speriment we will see what cola can do to your teeth and why we should brush them. The shell of an egg is very like the enamel our teeth are made from. So, we can use an egg for this experiment instead of our actual teeth.

You will need

  • Cola
  • A boiled egg
  • A glass
  • Toothpaste
  • Toothbrush
  • Water

How to do this experiment

  1. First, place the boiled egg carefully in the glass.
    An egg in a glass

  2. Pour enough fizzy cola into the glass to completely cover the egg.
    An egg in cola

  3. Leave for 24 hours or overnight.
    A clock

  4. Carefully take the egg out of the glass. You might want to use a spoon.
    Taking the egg out of the glass with a spoon.

  5. What has changed? How does it look? Does it feel different? Ours has a spot on it that is lighter than the rest. We think this might be where it sat on the bottom of the glass.
    An egg held in the hand

  6. Let’s see if we can clean it up! Put some toothpaste on the toothbrush.
    A toothbrush with toothpaste on it.

  7. Carefully brush one part of the egg, just like your were brushing your teeth.
    Cleaning an egg with a toothbrush.

  8. Rinse off the toothpaste to see if there’s a difference.
    The egg after brushing and rinsing.

  9. What has happened to the part of the egg you brushed?

Find out more...

The shell of the egg contains calcium carbonate, the same substance that is found in your bones and teeth. The acid in the cola reacts with the egg shell to produce and gas called carbon dioxide and a solid called calcium oxide. The dark colour on the shell is a mixture of this calcium oxide and the colouring from the cola. If the egg was left for long enough the shell would complete disappear.

Brushing the egg cleans off the colouring and calcium oxide. This bite is a good way to show children why they should brush their teeth.

Curriculum Links

Earth's Materials

SCN 3-17a

Body Systems and Cells

SCN 1-13a/ 3-13a


Glasgow Science Centre