Make a Fossil

Most fossils form this way: A living thing decays and leaves a mold in its own shape behind in the earth. Then rock forms inside the mold, creating a copy of the living thing. This activity will help your child understand how fossils form.


  • 4 cups plaster of Paris
  • 2 1/2 cups water
  • Disposable container
  • Old or disposable small baking pan
  • Petroleum jelly


  1. Mix 2 cups of plaster of Paris with 1 1/4 cups of water in a disposable container.
  2. Spread the plaster in the bottom of an old or disposable small baking pan to a thickness of about 1 inch.
  3. Wait about 2 minutes until the plaster begins to set.
  4. Coat your child's hand with petroleum jelly.
  5. Gently press his hand into the plaster just enough to dent the surface. Hold his hand in place for a few minutes, then remove it and let the plaster set until it's completely hard.
  6. Coat the hand-shaped mold with petroleum jelly.
  7. Mix up another batch of plaster and pour it into the mold.
  8. Let the plaster harden, then gently separate the "fossil" from the mold.
  9. If they don't separate easily, hold the pan upright and tap it lightly with a hammer.


Copyright © 2001 by Patricia Kuffner. Excerpted from The Children's Busy Book with permission of its publisher, Meadowbrook Press.

To order this book visit Meadowbrook Press.


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