Elephant Toothpaste

One of the popular booths at Engineering Expo 2019 was Elephant Toothpaste. This experiment is especially fun because it is surprisingly fast acting.

The Science Behind It

Yeast is added to hydrogen peroxide and when they touch, it creates a gas. Imagine the yeast is trying to make the hydrogen peroxide burp. Those pockets of gas get trapped in bubbles by the soap that is added.

What is yeast? It’s an enzyme. All enzymes have active sites that help reactions take place. Here, the yeast breaks down the hydrogen peroxide (H2O2) creating oxygen gas (O2) and water (H2O). The oxygen gets trapped in the soap creating bubbles. The more oxygen, the more foam.

Source: scientificamerican.com

Source: scientificamerican.com

The overall chemical reaction looks like this:

Source: socratic.org

Source: socratic.org


You will need:

  • Funnel

  • 16 oz. sturdy water or soda bottle

  • 1/2 cup 6% Hydrogen Peroxide

  • 1 tbsp yeast

  • 3 tbsp warm water

  • 1 tbsp dish soap

  • Food coloring (optional)

  • Measuring table spoon

  • Cup to stir water and yeast together

  • Container to hold the entire experiment

We used 15% hydrogen peroxide at the 2019 Expo and it was purchased at a hair care store. It’s like bleach, and should be used carefully. Be sure to ask for help from an adult if you are unsure. You can also use 6% or 3% hydrogen peroxide and will still work, but the reaction will be weaker.


  1. Layer some newspaper or paper towels under your large experiment container and then sett up your equipment in your container so that you have an easy clean up - and no stains on any furniture!

  2. Add 1/2 cup of hydrogen peroxide to the water bottle

  3. Measure out 1 tbsp of yeast and 3 tbsp of warm water and add it to the separate small cup

  4. Stir the yeast and water mixture. Set aside.

  5. Measure out 1 tbsp of soap and add it to the hydrogen peroxide in the bottle. Shake to mix.

  6. Select the color of food dye (if chosen) and have help from an adult to add the dye to the bottle. If you dribble the dye down the inside of the bottle, you will get stripes in the foam. If you want a one color foam, add the dye to the bottle and stir slightly. Use as many (or as little) drops as you’d like.

  7. All children should step away from the water bottle as the adults add the yeast and water mixture.

  8. Watch the foam grow!


Let us know how your experiment worked! Do you have any tips and tricks we may have forgotten? Comment down below for others who might want to recreate this fun experiment. Tag us in social media with how your kids reacted to the experiment!