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Safe Self-Carving Pumpkin Project

Self-Carving Halloween Jack-o-Lantern that Won't Blow Up

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The self-carving pumpkin demonstration involves carving a jack-o-lantern face with chemistry.

The self-carving pumpkin demonstration involves carving a jack-o-lantern face using an explosive chemical reaction.

Anne Helmenstine
The self-carving Halloween pumpkin project uses chemistry to carve a jack-o-lantern face. The traditional version of the project is somewhat dangerous, so here's how to perform a safe version of the project.

Safe Self-Carving Pumpkin Materials

If you can get it, this project is super-easy using dry ice. However, you can substitute baking soda and vinegar if you can't get dry ice. You just want to be able to generate enough carbon dioxide gas to pop a plastic bag, yet with enough time for you to close the bag and seal the pumpkin before the gas blow the bag.
  • pumpkin or squash
  • zipper plastic bag
  • dry ice
  • water

Set Up the Demo

  1. Carve a simple jack-o-lantern face in your pumpkin, but save the pieces.

  2. Make certain the pieces can move easily (like if they are being blown out from the inside, which is what you're going to make happen. If the pieces are thick, you may want to cut away some of the pumpkin on the back of each piece.

  3. Replace the pieces. If you did a good job, your pumpkin won't look carved. Chances are the pumpkin will at least show marks where the jack-o-lantern face would be, but that would be true with the original self-carving demonstration, too.

  4. When you are ready to carve your pumpkin, add a small chunk of dry ice and a small amount of water to a zipping plastic bag.

  5. Immediately seal the bag and place it inside the pumpkin. Tightly replace the "lid" of the pumpkin.

  6. The pieces will blow outward when the bag explodes. This is usually within a few seconds. If you want more time, omit adding water to the bag so it will take longer for the dry ice to sublimate and build up pressure. You may even be able to omit the bag altogether and either mix dry ice and water or else baking soda and vinegar in the pumpkin.

  7. If none or only a few of your jack-o-lantern pieces flew out, check the looseness of the pieces. If you are sure the pieces move easily then make sure you had enough dry ice in the bag. Once you have the project performing the way you like, you're ready to perform the demonstration in front of students or friends.
See the video of this project.

Safety Considerations

If you are using dry ice, remember it is extremely cold and can give you frostbite if you handle it for more than a couple of seconds. While the dry ice is safe in a plastic bag, don't enclose it in a rigid container, such as a plastic or glass bottle as these materials can rupture explosively, turning a safe project into an unsafe one. The baking soda and vinegar form of this project is fine for children to do on their own. Adult supervision is necessary when working with dry ice.

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