When fossils arrive from the field, they are encased in plaster jackets, and the rock, or matrix, which was deposited around the fossils. Fossil preparation involves cutting open the plaster jacket and removing this matrix surrounding the fossil.

The matrix may be soft and crumbly when the sand or mud is poorly cemented together, or it can be extremely hard when the sediments are well-cemented. Accordingly, a wide variety of tools is required to remove the matrix and stabilize the fossil. Commonly, dental tools are used to carefully pick away sediment near the bone, along with custom-made needles composed of carbide steel.

Preparators carefully select the materials used to strengthen or repair specimens. Adhesives, glues, and fillers must stand the test of time and not become brittle or discolored, just like the materials used to conserve works of art. The types of materials used are recorded in order to aid future preparators if further preparation or repair is required.

Watch as Justy Alicea, a senior preparator at the American Museum of Natural History, works on a specimen and then gives a tour of the Museum's fossil preparation lab.