I started making this easy erupting volcano cake years ago to amuse my friends and have fun at parties. There is no baking involved (unless you prefer to make your own angel food cakes) and kids especially enjoy it.
The Science Behind the Erupting Volcano Cake:
The trick to making this cake go off is (carefully!) combining dry ice (carbon dioxide) with hot gelatin. Dry ice is unusual in that it sublimates. Many substances go through three phases: solid, liquid and gas. Dry ice skips the liquid state and goes straight from a solid to a gas. When you add the dry ice to hot gelatin, it heats it up and sublimates quickly, producing fog in the process. As Appalachian State University mentions,
“The fog that seems to be coming off a block of dry ice is actually not the carbon dioxide itself but rather water vapor from the air, condensing due to the cooling effect of the carbon dioxide. This effect is especially pronounced in the moist air above a warm container of water; thus, putting dry ice in warm water not only accelerates its sublimation but creates a lot of fog.”
Pretty cool, eh? Let’s get into how to easily make your own erupting volcano cake.
Warning: Use proper precautions when handling dry ice to avoid injury. Wear gloves and use tongs. Also, do not eat gelatin in the cup as I find that there are still bits of dry ice for a while.
- 2 Angel food Bundt cakes (you can make your own if you like, but I just grab a couple from the store bakery to make it simple)
- 2 cans of chocolate frosting
- 1 small block of dry ice (about .5-1 pound will do)
- 1 box red gelatin (flavor of your choice)
- 2 cups hot water
- (Optional) Animal cookies or crackers
- (Optional) 1 can of white frosting
- (Optional) Blue food coloring
- (Optional) Sea life gummies like Swedish fish, octopi and frogs
- Cookie sheet
- Bread knife
- Butter knife
- Aluminum foil
Step 1: Line Cookie Sheet and Assemble Cakes
Use the aluminum foil to cover the cookie sheet. That will help keep the mess down and give you a nice base if you decide to add water. Remove the first cake and place it upside down on the foil (wider side down). Place the other cake on top in a similar fashion.
Step 2: Trim the Cakes into a Cone
Next, use the bread knife to start trimming down the top cake so that it forms more of a cone shape. Take off a bit at a time and make sure that you leave the edge around the center hole intact. Gently brush off crumbs. Don’t worry too much if it doesn’t cut perfectly as you can fix it with icing 🙂
Step 3: Add in the Plastic Cup
Carefully push a plastic cup into the top with a screwing motion. This will hold your hot red gelatin for the coming eruption. Don’t use a cup with a wider brim since narrower ones will help force the liquid upward faster.
Step 4: Frost Away!
Frost the sides of the cake with the chocolate frosting. I like to put on a lot in one spot to help cover the crumbs easier. If any get stuck on top, go over it with the knife again and they should get mixed in. The frosting also sometimes wants to come back off the angel food as you frost. Do not despair. Smooth it out and keep going. You should be able to cover it evenly to create the cone shaped volcano.
Optional But Fun: Decorate the Cookie Sheet
I don’t do this every time I make this cake, but it’s fun to add more decorations to the scene. Mix blue food coloring a few drops at a time into white frosting until it’s the shade that you want. Spread over the foil. Add sea critters; in this scene, there are Swedish fish, Haribo frogs and Trolli Sour Brite Octupus. If you are feeling saucy, you can add animal crackers to the side. I miss the dinosaur cookies that I used to be able to buy, since they seemed apt.
Step 5: Mix Up Gelatin and Add to Cup
Warm up 2 cups of water until it is hot, but not boiling. Add to your gelatin powder. You do not need to add cold water as mentioned on the package. Pour into the cup until it is about .5″ from the top. You want to leave room to add in the dry ice.
Step 6: Break Up Dry Ice
Be safe! Put on gloves for this part and use tongs to move it around since dry ice is incredibly cold (-109.3F!) and can burn if it touches your skin. Even if you get a small amount from the store, the chunks are usually too big. We want them to fit in nicely into the cup and be able to add more to keep the reaction going. You only need to gently tap the dry ice with a hammer to get it to break apart.
Step 6: Gather Everyone Around and Have Fun!
Use the tongs to add a chunk of dry ice to the gelatin in the cup. The reaction will start to produce fog that will roll over the sides. The gelatin will bubble up until it runs over the side and “erupts”. You can keep adding little chunks of dry ice until the gelatin sets up a bit. If you like, you could carefully remove and discard the gelatin in the cup (put in the sink) and add more to start again.
Warning: Do not eat the gelatin from the cup since it often contains bits of dry ice for a while.
Here’s a version that I did many years ago. Narration and editing by one of my favorite families.
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