|Display #4: What is a fossil replica?
When you go to see those dinosaurs at the museum, most of the
time you are not looking at the actual fossil. You are usually looking
at a cast.
There are several reasons for this, one of which being some kid can try to
"ride the dinosaur", have the whole thing collapse and have a really expensive
and irreplaceable fossil destroyed.
Sometimes there is only ONE of a particular fossil in the whole world.
Other scientists would like to study it, but it's hazardous to ship fossils
around and they can get ruined just by wear and tear. So a cast is made of the fossil.
A cast is made by a variety of methods. One of the most common materials
used is latex rubber. You can buy it as a thick liquid that you paint
onto the original fossil. Let it dry, then paint another coat on.
Do it over and over again, and soon you have a very thick rubber jacket that
peels off the original fossil and records even the most minute details of
Here is the original sigilaria fossil and the latex rubber mold removed from
Once the mold is made, a copy of the fossil can be made by pouring plaster
of paris or liquid plastic into the mold. Once it has set, the latex
mold is removed, and voila! A fossil cast that looks identical to the
Sometimes the fossil can be quite large - too big for the rubber to support
itself. So in cases like that, a mother
is made, usually of plastered gauze - the same tough stuff they
make a cast for your broken arm out of. The mother cast is made on
the outside of the latex mold to support the soft rubber.
Both the mother cast and the latex mold are
made in sections which can be removed from each other for filling the mold
and de-molding. Index bolts, pins or little rubber pyramids are used
to keep everything aligned perfectly.
The Creation Science Museum of Canada has both real fossils and fossil casts.