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Molds and Casts

a steinkern

 

Many of the gastropod (snail) fossils found in Austin are 'steinkerns' - internal casts of the original organism.


Paleontologists use a similar process to create casts of fossils for display purposes or for research.  The series of images shown below illustrates the steps in the creation of a cast of a 'breadfruit' leaf.

The original block with the thin carbonized imprint of a leaf on the surface is fragile, and would disintegrate if displayed. 

This is one instance where the NPL would make a cast rather than display the actual specimen.

original breadfruit leaf
the mold

The block with its leaf is thinly coated with a separating material, to protect the specimen and keep the molding material from sticking.  Then liquid latex is painted on to make a mold.

The mold is filled with casting compound, usually plaster of paris or plastic resin.

a silicone compound was used to make this cast
the unpainted cast

The cast is removed from the mold, and carefully painted to resemble the original specimen.

The original fossil and the painted cast are shown below, side by side.  Can you tell the two apart?  Place the cursor over the images to find out whether you were correct!

the cast the original

 

 

Frequently used abbreviations: NPL  Non-vertebrate Paleontology Laboratory | TNSC Texas Natural Science Center | UTDGS Department of Geological Sciences | BEG  Bureau of Economic Geology | VPL Vertebrate Paleontology Laboratory | JSG  Jackson School of Geosciences | SUPPORT | VOLUNTEER | GLOSSARY


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