A volcano of foam

This week Sloan and Jay create a couple of foam volcanoes using a solution of concentrated hydrogen peroxide and some dish soap. Using super concentrated solutions allows the reaction to happen so fast that the foam literally hits the ceiling in our demonstration theater. Check out the video.

You may have heard this reaction called “Elephants Toothpaste” if you’ve taken a chemistry class or visited the science center. Sometimes we do this reaction in a tall straight cylinder so when the foam comes out the top it looks like what a giant tube of toothpaste must look like when and elephant steps on it. Whatever you call it, it’s a fun chemical reaction that creates a huge blob of soapy foam that everyone loves. The version in the video above uses a very concentrated (35% concentration) solution of hydrogen peroxide. Unless you’re a teacher or science museum it’s difficult to obtain the 35% hydrogen peroxide needed to do this experiment. Also, because it’s so concentrated you have to be very careful not to get it on your skin. The peroxide you can buy at a drug store and use for small cuts and scrapes is a 3% solution. There is a smaller version you can do at home or in your classroom that uses the 3% peroxide you may have at home.

The Science and a version you can do at home

The basic science here is that you have hydrogen peroxide, which could be called hydrogen dioxide, since it is just a water molecule with an extra oxygen atom attached.  Hydrogen peroxide is H2O2, water is of course H2O. By adding another chemical, called a catalyst, to the peroxide, you start  a chemical reaction that releases the extra oxygen attached to the water molecule. If you mix in a little dish soap you can capture the released oxygen gas in the form of bubbles.

Here’s what you need

  • an empty 16 oz. plastic soda or water bottle
  • 1/2 cup 3% hydrogen peroxide
  • Dish detergent
  • Food coloring
  • 1 teaspoon (or half a packet) of yeast dissolved in warm water

Fill your soda bottle with the 1/2 cup of peroxide and then add a squirt or two of dish detergent. If you want, you can also add a squirt of food coloring to make things a bit festive. Now you need to prepare your yeast. Actually you have a couple of options, you could just pour the dry yeast into the bottle. This will create a surge of foam from the bottle with large bubbles. The yeast acting as a catalyst to release oxygen from the hydrogen peroxide. However, if you want a rich creamy foam of tiny bubbles, you should really add your teaspoon of yeast to a few tablespoons of warm water, then add the liquid to your bottle.

If you have ever made bread from scratch, you know that adding yeast to warm water allows the yeast to multiply into a somewhat smelly and foamy froth of more yeast cells. When you add this liquid to the peroxide you will get quite a surge of tiny soapy bubbles. The bubbly mixture is simply detergent, water, and oxygen filled bubbles and quite safe to touch. In fact you might observe that the foam is warm because this reaction is exothermic, meaning giving off heat.

Play around with the amount of peroxide, detergent, yeast and bottles to create the best geyser of foam! If you try this experiment or have any questions about the science, leave us a comment below.

About the author

Carl Nelson is the Chief Scientist at Imagination Station in Toledo, Ohio. He holds a Masters Degree in Experimental Physics from Michigan State University and has been having fun exploring (exploding?) science in Science Centers for the past 20 years.


13 Responses to “A volcano of foam”
  1. Dinah says:

    What would it be like if you just mixed yeast and soap?

  2. Carl says:

    Well, we are using sodium iodide as a catalyst to accelerate the breakdown of the hydrogen peroxide in to water and oxygen gas. You could use yeast as a catalyst, it just won’t create a huge geyser of foam like the sodium iodide will. It’s still pretty cool, just on a smaller scale.


  3. Trent says:

    What I used aluminum chloride as the catalyst?

  4. Carl says:


    I’ve never used aluminum chloride as a catalyst for this reaction. If you try it let me know how it works.


  5. Alex says:

    Hi Carl

    is there a chemical equation that explains the formation of the foam?

    thank you!

  6. Alison Galia says:

    Hi i am a science teacher in australia and I am wondering what concentration (molar) you’re using for the Sodium Iodide

  7. Carl says:

    Hi Alison, we typically use a 2 Molar solution of Potassium Iodide (we sometimes use Sodium Iodide as well, same molarity). Sometimes we use a 4 molar solution when using the 4 liter flask version of the demo.

  8. Allison says:

    What are the measurements/ingredients to the 35% hydrogen peroxide explosion? I have obtained the liquid, and would like to do this experiment.

  9. Jenny says:

    We can’t seem to get the geyser action to happen, we are using the 3% peroxide and warm water to activate the yeast. what might we be doing wrong?

  10. Carl says:

    Hi Jenny,
    Are you using fresh peroxide? The 3% solution combined with yeast should create a gentle foaming of liquid. It will not create a shooting geyser like the 35% peroxide we used because it does not generate enough oxygen gas.

  11. jalaal says:

    thank you really helped

  12. Marielle says:

    Hey, what happens if there is no dish detergent?

  13. Carl says:

    Hi Marielle,
    The soap is there to capture the oxygen gas that comes from the decomposition of the hydrogen peroxide. With no soap there would be a large plume of hot oxygen gas and water vapor generated. As that cools it will form a plume of fog. This variation of the demonstration we call, “Genie in a bottle”. Since it kinda looks like a Genie being released from a bottle.

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