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How to Make a Fossil Bed in Plaster of Paris

Fossils fall into two main categories: mold and cast. A mold is the imprint of an object--often shells but sometimes bones or plant matter. When sediment fills the mold and hardens, it becomes a cast. A cast is a three-dimensional rendering of the original item that created the mold. Making your own fossil bed with plaster of Paris first requires a mold. The plaster then emulates the sediment layer that fills the mold, rendering the fossil bed cast in the plaster.

Things You'll Need

Aluminum pie pan
Modeling clay
Shells and fossil items
Bowl
Plaster of Paris powder
Disposable spoon
Towel

Instructions

- 1
  Fill an aluminum pie pan with 1 to 2 inches of modeling clay. Press the clay into all corners of the pan then smooth the surface so it is completely flat.
- 2
  Press shells, stones, bones and other small objects into the clay then lift them straight up, leaving an impression in the clay. Do not wiggle the objects as you lift, as this will ruin the detail left behind in the clay.
- 3
  Pour the water into a disposable bowl then sprinkle the plaster of Paris powder into the water, using a ratio of one part water to two parts plaster, covering the entire water surface. Allow the plaster to settle for one minute then stir it slowly until smooth.
- 4
  Pour the plaster over the clay, covering the entire surface. First fill the fossil molds then pour the plaster over the rest of the clay, burying it to a 1 or 2 inch depth. Allow the plaster to harden completely according to package directions, usually for two to three hours.
- 5
  Turn the pie pan upside down on top of a towel. Lightly tap the bottom to loosen the plaster then lift the pan up, leaving the plaster fossil bed on top the towel.
- 6
  Scrape any remaining clay out of the plaster cast and pie pan and set it aside for another use. The fossil bed should show the details on its surface of the fossils you pressed into the clay mold.

Rocks & Minerals