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How to Create a Cast & Mold of a Fossil

Scientists cast and mold fossils to use in museums, and so that they do not have to remove huge slabs of solid rock. The basic technique is similar to that for any other cast or mold. The key difference is the detailing in the mold, as each fossil must be captured perfectly, with all its features clear to see. If you do it correctly, you can create a perfect replica of the fossil that will last for years.

Things You'll Need

Modelling clay
Cardboard
Sticky tape
Plaster powder
Water

Instructions

- 1
  Mold the modelling clay into and around the fossil. The clay should be 1 inch thick and must be firmly pressed in so all the details of the fossil are captured.
- 2
  Carefully peel away the clay so as not to damage the fossil imprint.
- 3
  Wrap a piece of cardboard around the edge of the clay and secure with sticky tape. This cardboard acts like a dam for the plaster.
- 4
  Combine together the plaster power with water to make a liquid paste. This is normally two parts plaster to 1 part water. Make sure the two elements are mixed well before pouring it into the mold.
- 5
  Pour the plaster into the modelling clay. Leave it to harden for one hour before removing the cardboard dam.
- 6
  Leave the plaster to set for two days before separating the clay from the plaster cast.

Fossil Collecting