My Work After the bones and fossils are brought back to the museum, they are cleaned and sorted. Then some copies have to be made. This is part of my job.
Why do we make copies? Many bones and fossils are one of a kind. If something happened to them, this would be a great loss. That’s why we make a copy. We make copies so that scientists can study the fossils without having to always handle the real specimens. Copies of fossils and bones can be loaned to scientists and museums around the world. We don’t risk damaging the real ones if they are moved. The dinosaur skeletons you see in museums are copies. The real fossil bones are much too heavy to use. This is because they consist of rock. Human bones don’t just stay in place on their own. They are held together with muscle and skin. We don’t have any dinosaur muscle and skin in our collection. I wonder why not?
Making fossil and bone moulds 1. First I make a plasticine base to hold the fossil in place.
2. I build a slab under the bottom half of the bone or fossil. I work on the top half that you can see. Then I build a wall around it to catch the runny mould material so the wall needs to be watertight. Wall Slab
3. I pour in a thin layer of runny silicon rubber. It fills up all the spaces around the fossil - every crack and feature. I let the first layer dry. Then I pour in more layers until it is covered. Wall Slab
4. When the fossil is completely covered with runny silicon rubber, I spread thick silicon rubber over the other layers. Silicon rubber comes in different colours. I remove the wall of plasticine when it is dry.
5. I then cover this half of the silicon mould with plaster, a bit like the plaster used to make a cast for a broken arm. This goes over the silicon and rests on the plasticine slab. I leave this to dry.
6. Then I turn the half mould upside down so that the plaster is at the bottom. I take all the plasticine off the top and I am left with the fossil in a mould of silicon rubber (pink) and plaster (grey). Hard plaster Mould flipped Silicon rubber
7. I completely cover the flat silicon and plaster surface around the fossil with a thick layer of grease that looks like hair gel. This is the area shaded with black lines. Why do you think I do this? The layer of grease stops the two sides of the mould sticking together.
8. Then I make another plasticine wall on top of the greased bottom section. I begin to cover the other half of the fossil with silicon layers in the same way as before.
9. Finally I take off the plasticine wall and cover the top half in a different coloured plaster. This way I can tell where one half meets the other. I leave it to dry so that its hard.
10. When the mould is really dry, I can slide a tool in between the two halves. They open easily because of the grease. I take out the real fossil which has been protected by silicon rubber. It leaves an exact matching shape in the mould.
Why have I done this? Now I can pour a resin into the mould halves and it will harden in the shape of the fossil. Then I remove them and glue them together carefully to make…