Name: __________________________________
Fossils:
Creating Molds and Casts
Purpose (Why are we doing this?):
To observe a mold and a cast in the
creation of a fossil.
Procedure (What do we need to do?):
Materials (What do we need?):
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Permanent marker
Paper towel
Cup
Chunk of clay
Popsicle stick
Petroleum jelly (Vaseline)
Stamper
Plaster of Paris
Water
1. Write your name on your cup using the permanent marker.
2. Set up your work station by placing a paper towel under your cup.
3. Roll your chunk of clay into a ball and place it in the bottom of your cup. Flatten
the clay out so that it covers the bottom of your cup and takes up less than half of
the volume of the cup.
4. Spread petroleum jelly (Vaseline) over your stamper to keep the clay from
sticking.
5. Use your stamper to create an impression in the clay. Remove the stamper from
the clay.
6. Add ½ cup of plaster on top of the impression you made in the clay.
7. Add 2-3 tablespoons of water and stir with the popsicle stick. The consistency
should be thick, not runny! If yours is too runny, quickly add a small amount of
plaster and stir.
WARNING: Do not poke the clay with your popsicle stick. This can
mess up your fossil!
8. Carefully carry your cup to wherever Miss Holden tells you to take them so that
they can dry.
9. Clean up your work space.
Day 2 Procedure:
1. Carefully tear the cup away from your fossil over a trash can.
2. Return your clay to Miss Holden.
3. Clean up anything that needs cleaned up.
Name: __________________________________
Results (What happened?):
Day 1: Which is the mold? Which is the cast? How are they similar and different?
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Day 1: What characteristics of your stamper can you see in the mold?
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Day 2: What characteristics of your stamper can you see in the cast?
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Explanation (Why did this happen?)
Day 2: Compare the characteristics you saw in the mold to the characteristics you saw
in the cast. Why did this happen?
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