I am a Scientist

Technical Officer-

Palaeontology

Created By QM Learning 2012

I am a technical officer

Hi. My name is Debra.

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…

… a copy of the fossil.

Then with some paint…

… can you guess

which is the real

one?

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Images © Queensland Museum