Spooky Science for Halloween

Dry ice and sublimation make an eerie party prop.

I’m not really into theme science projects — I think they tend to distract kids from the science that’s happening — but like any good mad scientist, I make an exception for Halloween. Every year, we host a Halloween pre-trick-or-treating party for our neighborhood, and every year, the kids insist we fill the garage with bouncing smoke bubbles. I pulled this experiment out on a whim the first year we did this, thinking it would be a cool way to fill up our witch’s cauldron. It’s become an essential piece of our Halloween tradition. The costumes have changed from dinosaurs and Harry Potter to Avengers and anime characters, but the “smoke bubbles” stay the same.

The “smoke” is actually carbon dioxide made with dry ice, and the hardest part of this project is making the machine that does this. (See the instructions below.) Dry ice is pretty cool because it sublimates — it turns directly into a gas with no liquid stage in between. Give yourself plenty of time for a few practice runs. (And remind yourself that failure is part of the process!) It’s not hard, but you may need a few tries to get it just right.

This year, I’m planning to push the science a little further: I’ve bought a bunch of winter gloves, and I’m going to see if we can play some smoke bubble catch. I expect things to get a little messy and rambunctious — and frankly, I’m looking forward to it!

How to Build a Dry Ice Bubble Maker

WHAT YOU NEED:

• Safety glasses

• Knit gloves

• Gallon-sized plastic jar with a lid

• 3-foot piece of rubber

• tubing

• Duct tape

• Liquid soap (Dawn works best) X Small plastic container

• Dish soap

• Dry ice

• Thick gloves

• Bath towel

What to do:

• Drill a hole near the top of the jar, and attach the plastic tubing to the jar with duct tape. (Basically, you’re making a place for the carbon dioxide to blow out of the jar, through the tube, and into your balloons.) Leave the lid off.

• Put on your gloves and safety glasses. (You should never skip this step, but especially don’t skip it this time.)

• Break up your dry ice into pieces that will fit into your jar. (I use a hammer for this.)

• Fill the open jar half-full with warm water.

• Drop a few chunks of dry ice into the water. You’ll see fog immediately, so experiment with using the lid to direct the flow of fog through the tube. (You probably won’t need to actually twist the lid onto the jar to get the flow you want.)

• Don’t ever seal the jar and the tube/vent at the same time! If you do, the pressure will build up, and the jar could explode.

• Now you’re ready to make your bubbles: Add a generous squirt of dish soap to a cup, and mix thoroughly with about 4 ounces of water. Dip the loose end of your tubing into the soap, just as you would a bubble wand. Slowly remove the tubing from the soap mixture, and adjust the lid of your jar to form a bubble with the gas. (You’ll probably want to practice this a few times to get the hang of it, but once you get a rhythm down, it’s pretty fun.)

• When the bubble is the size you want, gently shake it off the tubing. It will be heavier than a normal bubble and fall right to the floor, setting off a cool fog explosion, so be prepared.

Misty Heaslet is a middle school science teacher turned homeschool mom. She lives in western North Carolina. This column originally appeared in the fall 2019 issue of HSL.

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