Make Delicious S'mores With a DIY Solar Oven

Learn how to harness the energy of the sun to make ooey-gooey s'mores. Kids will love this fun (and tasty) science experiment.

Photo by: Debbie Wolfe

Debbie Wolfe

Here's an enjoyable DIY project that'll teach your kids about thermal energy. I love any opportunity to combine learning and fun together in one activity. This experiment is simple and doesn't require many supplies. Plus, the kids get to have a tasty treat at the end, so it's a win-win for everyone.

What You'll Need

  • cardboard box with attached lid, at least three inches deep
  • heavy-duty aluminum foil
  • clear plastic wrap
  • glue stick
  • utility knife
  • tape
  • ruler
  • pencil or marker
  • graham crackers
  • marshmallows
  • chocolate
  • small aluminum pie pan

Photo by: Debbie Wolfe

Debbie Wolfe

Any type of lidded cardboard box will work. It just needs to be at least three inches deep and wide enough to hold a pie pan. Shoeboxes are perfect for this activity.

Cut the Flap

Mark a one-inch border around three sides of the top of the box. Use the utility knife to cut out the flap.

Photo by: Debbie Wolfe

Debbie Wolfe

Line the Inside

Spread a coat of glue on the inside (bottom) of the flap, then cover with aluminum foil. Line the inside of the box with aluminum foil, gluing it down and making it as smooth as possible.

Photo by: Debbie Wolfe

Debbie Wolfe

Cover With Plastic

Tape one layer of plastic on the base of the box underneath the lid. You only need to tape down one side of the plastic. Leave the opposite side open so you can insert the pie pan later.

Photo by: Debbie Wolfe

Debbie Wolfe

Tape another layer of plastic across the top of the box, covering the hole you cut out, right underneath the foil-lined flap. Tape down both sides and make sure it's secure.

Photo by: Debbie Wolfe

Debbie Wolfe


Set the solar oven in the direct sun. Prop the flap open with a pencil. This will reflect the light into the box, helping it to heat up. Preheat the oven for at least 30 minutes.

Photo by: Debbie Wolfe

Debbie Wolfe

Cook the Marshmallows

Break graham crackers in half and place them onto the pie pan. Place a marshmallow on each graham cracker square. You'll need to cook the marshmallows first because it takes longer for them to melt than the chocolate. Gently lift the lid and the lower plastic cover and place the pie pan into the oven. You should feel some of the thermal heat already!

Photo by: Debbie Wolfe

Debbie Wolfe

Replace the plastic layers and prop up the flap with the pencil. Depending on how much sun there is and how hot the day is, the marshmallows can take about 30 minutes (or more) to get soft. Once they are soft, add the chocolate squares and the other graham crackers.

Why It Works

Here’s the science behind how the solar oven works. When thermal light energy from the sun enters your oven, the foil in the box reflects the light (heat), concentrating the heat into your oven. The marshmallows are cooked during absorption when the heat (energy) is transferred into the marshmallow. This simple oven works because the cardboard and plastic wrap insulate the oven. In short, you’ve made a tiny convection oven—the heat is trapped in the oven and flows around the marshmallows, cooking them.

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