Leaky Pumpkin

Leaky Pumpkin

If you have a ton of rotting pumpkins on your porch, try this to get one last use out of them before you throw them away!

This leaky pumpkin foams up all over the place because of a special organism called yeast. Yeast is a type of fungus, and it’s normally used by people to make bread rise and make drinks ferment. For the leaky pumpkin, we use it to make all the bubbles for the foam. A little bit of warm water is all that’s needed to get the yeast ready to work.

Yeast makes a special molecule that reacts with hydrogen peroxide. Hydrogen peroxide (H2O2) is like a molecule of water that has one extra oxygen on it. When the yeast reacts with the hydrogen peroxide, it strips off one of those oxygen atoms and turns the hydrogen peroxide into water. H2O2 becomes H2O + oxygen gas. The yeast does this reaction VERY quickly - one yeast can break apart over a million H2O2 molecules in one second.

As all that oxygen gets released by the yeast, it bubbles into the dish soap and makes a thick foam. The speed of the reaction pushes the foam out of the holes in the pumpkin, giving this spooky Halloween tradition an added fright factor!

5 - 16
Est. Time:
<30 mins

How we did it:

Materials List

  1. jack-o'-lantern
  2. hydrogen peroxide - 6% or 20 volume
  3. dry yeast (1 tablespoon)
  4. warm water (3 tablespoons)
  5. dish soap (1 tablespoon)
  6. food coloring
  7. small cups (2)
  8. measuring cup
  9. tablespoon measure
  10. safety goggles
  1. Gather your materials, put your safety goggles on, and head outside!

  2. Open up the top of your pumpkin and pour in 1 tablespoon of dish soap. 

  3. Drip in 8-10 drops of food coloring.

  4. Pour in ½ cup of hydrogen peroxide.

  5. Mix 1 tablespoon of dry yeast and 3 tablespoons of warm water for about 30 seconds to 1 minute. 

  6. Quickly and carefully pour this mixture into one of the holes in the jack-o’-lantern. Then, watch your pumpkin begin to leak! Keep experimenting! Try doubling the recipe or using a jack-o’-lantern with smaller or bigger holes. 

  7. Learn More!

    Different amounts of the ingredients used in this project can change how your leaky pumpkin foams up. Turn this project into an experiment by using more or less yeast, or more or less dish soap. What effect does this change have on your leaky pumpkin’s foam?