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.

Courtesy of Mt. Blanco Fossil Museum & Casting Company

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 the fossil.

Here is the original sigilaria fossil and the latex rubber mold removed from it.

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 original!

Sometimes the fossil can be quite large - too big for the rubber to support itself.  So in cases like that, a mother cast 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.


The Creation Science Museum of Canada has both real fossils and fossil casts.