A unit on dinosaurs hardly seems complete without talking a bit about fossils! The common way of using plaster of Paris to make hardened imprints seemed a bit daunting to me, particularly when I read through the warning label, not to mention the mixing, the mess, and a number of excited preschoolers involved in the process. For our dinosaur unit we made fossil imprints using baking soda clay. I simply made the clay the night before and left it in a sealed Ziplock bag. After reading our dinosaur book and talking about fossils in small group, each child was given a paper plate and a small ball of soda clay to flatten. Then they could choose from plastic dinosaurs to make footprints and/or large seashells to press in for a texture print. I also included a note explaining to parents that the clay needed to air dry at least overnight to harden to it’s “fossilized” state. (Hopefully, you can see the imprint in the picture above. If I had been thinking more about photography than preschool, I would have gone for a little more color interest here!)
The children enjoyed making their own fossil imprints, while they also gained science knowledge about dinosaurs, and the formation of the evidence of them that remains today. Language skills increased as they talked about their own creations and incoporated new terms, such as “imprint”, “fossil”, and “trace”. I enjoyed watching them experience all of this without having to chip plaster of Paris out of my carpet, or someone’s beautiful braid! Here’s the recipe so you can try it out for yourself!
Baking Soda Clay
2 cups baking soda
1 1/4 cup water
1 cup cornstarch
Combine all ingredients in a pot. Add color if desired. Stir while heating on low for about 15 minutes. Remove from heat and continue stirring. When it begins to look like mashed potatoes, it’s ready! Store in an air-tight container until ready to be used. Clay dries in about 12 hours (depending upon the thickness of the creation.) Once dry, the clay can be painted or colored with markers!