Making a Fossil

Something strange is happening at EHS this week.  Time seems to be speeding up and fossils are forming in 1 hour instead of millions of years.

Well - not really.  We have been making models of fossils.  A mould fossil to be exact.

A mould fossil occurs when a bone, shell or footprint has left a print in the rock where it had been.  The bone or shell is no longer there because it has dissolved or rotted away.  All that remains is the space where it once was.

To make our own mould fossils this is what we did:

1. Choose a shell and cover it with a thin layer of petroleum jelly.  This will stop it sticking.
2. Choose a small container that the shell will fit into.  Smear a thin layer of petroleum jelly inside the container.  A plastic cup works really well.
3. Next you have to work quickly.
4. Mix up some plaster of paris with cold water until you get a gloopy plaster mix.
5. Add a spoonful into the bottom of your cup and tap the cup on the table to get a smooth surface on the plaster.
6. Now gently lower the shell on top of the plaster.  Don't push it down too far or it will be hard to remove later.
7. Leave the fossil to set for at least 1 hour.  
8. Now it is time to uncover the mould fossil.
9. Carefully tap the plaster from the cup and take off the shell.
10. You will be left with a mould in the shape of your shell.