Elephant toothpaste is a chemical reaction that makes a volcano of foam when soapy water traps gases from the rapid decomposition of hydrogen peroxide. There are two easy methods for making elephant toothpaste. One makes a giant mountain of foam, while the other produces a smaller effect but is safe enough for kids to touch. The dramatic reaction uses strong peroxide and potassium iodide, while the kid-friendly version uses dilute peroxide and replaces potassium iodide with yeast. Here are instructions for both methods and a look at the chemistry involved.
Why Is It Called Elephant Toothpaste?
First, you may wonder why the reaction has the name “elephant toothpaste.” It’s because the thick column of foam escaping a tube looks like toothpaste big enough for an elephant to use. Also, it’s a lot easier and more descriptive than calling the reaction “rapid decomposition of peroxide”. After all, the point of elephant toothpaste is engaging people in the wonder of science. Even if someone doesn’t understand the chemistry, the project is fun and entertaining.
How to Make Giant Elephant Toothpaste
When you see videos of the world’s largest elephant toothpaste, you’re viewing the classic version of the demonstration.
This version uses concentrated hydrogen peroxide, potassium iodide or sodium iodide, liquid dishwashing detergent, water, and (if desired) food coloring:
- 30% hydrogen peroxide (H2O2)
- Potassium iodide (KI) or sodium iodide (NaI)
- Liquid dishwashing detergent
- Food coloring (optional)
- Large graduated cylinder or Erlenmeyer flask
- Tray or tarp to catch the foam
The chemicals are available online, although it’s easier to just pick up the peroxide at a beauty supply store. Choose any tall container for the demonstration, but use glass and not plastic because the reaction generates heat.
Start by putting on proper safety gear, including safety goggles and gloves.
- First, prepare a saturated solution of potassium iodide or sodium iodide in water. In a beaker, dissolve crystals of either chemical in about 120 ml (4 ounces) of water. Continue stirring in the solid until no more dissolves. It takes about a tablespoon of the dry chemical. But, measurements are not critical here. Set aside the solution for now.
- Set the cylinder or flask in a tray or on a tarp. Pour about 60 ml (2 ounces) of 30% hydrogen peroxide into the glass tube. Add a squirt (about 5 ml) of dishwashing liquid to the tube. If you want colored foam, add a few drops of food coloring. Swirl the liquids to mix them. Here again, exact measurements are unnecessary.
- When you’re ready for the reaction, pour about 15 ml (one tablespoon) of the iodide solution and stand back. Foam forms within seconds and rapidly escapes the tube.
- After the reaction ends, wash the contents of the tray and tube down the drain with water.
Kid-Friendly Elephant Toothpaste
The classic chemistry demonstration is for chemistry educators, but the kid-friendly elephant toothpaste is safe enough for parents and children to perform and touch. Also, this version uses easy-to-find ingredients.
- 3% household peroxide
- 1-2 packet of dry yeast
- Liquid dishwashing detergent
- Food coloring
- Empty plastic soft drink bottle
- Cookie sheet or pan to catch the foam (optional)
It’s not necessary to don safety gear for this reaction and it’s fine to use either a plastic or glass container. Just make sure the bottle has a narrow opening because this channels the foam and improves the effect.
Don’t worry about measuring ingredients precisely.
- Pour about a cup of 3% hydrogen peroxide into an empty bottle. If the bottle opening is small, use a funnel.
- Add a couple of squirts of dishwashing liquid and a few drops of food coloring to the bottle. Swish the liquid around to mix it.
- In a separate container, mix together yeast with enough warm water that the liquid is easy to pour. A paper cup is a great container choice because you can pinch its rim and make pouring the yeast mixture easier. Wait a couple of minutes before proceeding so the yeast has a chance to activate.
- When you’re ready, place the bottle on a cookie sheet or pan and pour yeast mixture into the bottle
- Clean-up using warm, soapy water.
Is Elephant Toothpaste Safe to Touch?
You can handle the ingredients and the foam from the kid-friendly elephant toothpaste project. However, don’t touch either the ingredients or the foam from the classic giant elephant toothpaste. This is because the peroxide is concentrated enough to cause a chemical burn, while the giant toothpaste is hot enough to cause a thermal burn.
How Elephant Toothpaste Works
The basis for the elephant toothpaste display is the rapid decomposition of hydrogen peroxide (H2O2). Hydrogen peroxide naturally decomposes into water and oxygen gas according to this chemical reaction:
2H2O2(l) → 2H2O(l) + O2(g)
In a decomposition reaction, a larger molecule breaks down into two or more smaller molecules. The normally slow progression of the reaction is why a bottle of peroxide has a shelf life. Exposure to light accelerates the decomposition, which is why peroxide comes in opaque containers.
Either potassium iodide or the enzyme catalase (found in yeast) acts as a catalyst for the reaction. In other words, either of these chemicals supercharges the reaction so it proceeds very quickly. Breaking chemical bonds in peroxide releases a lot of energy. Only a fraction of this energy goes back into forming chemical bonds making water and oxygen. What this means is that elephant toothpaste is an exothermic reaction or one that releases heat. How hot the reaction gets depends on how much peroxide you start with and how efficiently the catalyst speeds up the reaction. So, the classic version of the project gets hot enough to steam. The kid-friendly version of elephant toothpaste gets warm, but not hot enough to cause a burn.
Producing gas isn’t enough to make a foamy volcano. Adding liquid soap or dishwashing detergent to the mixture traps the gas bubbles. Normally, the reaction doesn’t have much color. Using food coloring makes the foam more interesting. Depending on your choice of colors, it also makes the foam resemble toothpaste.
- Dirren, Glen; Gilbert, George; Juergens, Frederick; Page, Philip; Ramette, Richard; Schreiner, Rodney; Scott, Earle; Testen, May; Williams, Lloyd. (1983). Chemical Demonstrations: A Handbook for Teachers of Chemistry. Vol. 1. University of Wisconsin Press. Madison, Wisconsin. doi:10.1021/ed062pA31.2
- “Elephant’s Toothpaste.” University of Utah Chemistry Demonstrations. University of Utah.
- Hernando, Franco; Laperuta, Santiago; Kuijl, Jeanine Van; Laurin, Nihuel; Sacks, Federico; Ciolino, Andrés (2017). “Elephant Toothpaste”. Journal of Chemical Education. 94 (7): 907–910. doi:10.1021/acs.jchemed.7b00040
- IUPAC (1997). “Chemical decomposition”. Compendium of Chemical Terminology (the “Gold Book”) (2nd ed.). Oxford: Blackwell Scientific Publications. ISBN 0-9678550-9-8. doi:10.1351/goldbook