Fossils
a model
To understand what happens and how fossils are formed we have tried to "build" one and please do it with us.
1) take the shell of a common "core" (Cardium edulis) with both its valves (trovere it easy to be white, more suitable for this purpose)
2) prepared by kneading a bit of chalk with a little water to make a smooth paste and semi-solid.
3) pour a ball between the two halves and press firmly to close them
4) inserted between the two halves of a sctriscia cm wide paper. 4-5
5) Cover the shell with a layer of plaster often cm. 2-3
6) allowed to dry few hours and then separate the parts of plaster external (external mold),
the shell (real fossil), and the inside (internal cast)
If you want a more accurate model of Cernit can use instead of plaster, it is a plastic material (art shops) that molds like clay and baked in the oven at home at low temperature is similar to ceramics.
Then remember to do many tests to get better results.