Did you know the Black Hills are full of fossils? In fact, some of the most complete T. Rex fossils to date have been found in western South Dakota, not to mention the world-famous Mammoth Site in Hot Springs.

While paleontologists go through special training to dig up fossils, you can do it at home with this fun craft. This is a fun way to do hands-on learning without leaving your kitchen, and works great when paired with a field trip to one of the great museums around the hills that showcase fossils.


  • ½ cup baking soda
  • 1 cup Cornstarch
  • Water
  • Food coloring or almond flour (optional)
  • Plastic dinosaurs
  • Baking container 
  • Excavating tools (silverware, paintbrushes, etc.)


  • Preheat your oven to 250 degrees F 
  • Mix the cornstarch and baking soda together in your baking dish. If you’re using a larger dish, you can double or triple the recipe. The ratio is what’s important. Optional: add food coloring to make your mix look like dirt. We swapped out a cup of cornstarch with almond flour to make ours.
  • Add water to the mix until you have a sludge consistency. It should be slimy, but not runny.
  • Submerge the dinosaurs into the mixture, making sure they’re mostly covered
  • Bake in the oven until the mixture hardens. Be patient! It can take about an hour depending on your baking dish.
  • Once the mixture is hard, remove from the oven and allow to cool completely. When it’s ready, dig in! 

Questions you can ask to guide learning:

  • What is a fossil? (the remains of an animal formed when layers of dirt and rock build on top of each other and turn the animal into hard rock)
  • What part of the animal creates a fossil? (bones, shells, and teeth)
  • How long does it take for a fossil to form in nature? (at least 10,000 years or longer)
  • Are animals the only fossils? (no, plants can be fossils too, such as petrified wood)
  • Why do paleontologists use small tools like brushes? (so they don’t damage the fossil)

Proudly sponsored by The Mammoth Site, a world-renowned research and interpretive site in Hot Springs, South Dakota.