Interview with Preparator Amy Henrici

Q. What is a preparator?

A. A preparator (pre-PARE-uh-tor) uncovers fossils from the rock that surrounds them. The surrounding rock is called matrix. Preparators also repair fossils that have been damaged, make replicas (casts) of original fossils, and use a microscope to find and remove small fossils from crumbled matrix or sand.

Q. It all looks the same! How can you tell the fossils from the rock?

A. It's not always easy, but, to a trained eye, fossils do look different than the surrounding matrix. Some fossils look shiny, while some are a different color or a different texture than the matrix.

Q. How long does it take to dig out the fossils?

A. If the fossils are small—like Coelophysis teeth—it can take a couple of days just to work away an area the size of a deck of cards! Even if the fossils are larger—like a Diplodocus leg bone—it can still take a few days to work away an area the size of a box of cereal. The hardness of the matrix can also affect the preparation time. It sometimes takes years to uncover one large animal or a group of smaller animals.

Q. How do you get the fossils to the museum?

A. In the field, fossils and the surrounding rock are enclosed in a "jacket" made of plaster and burlap. This helps keep them intact during removal and transport from the dig site. This is the same method that was used more than 100 years ago on Diplodocus carnegii. Crates are carefully built around plaster-jacketed fossils—the combination of fossil, matrix, and crate can weigh thousands of pounds! Back at the lab, preparators open the plaster jacket and set to work exposing the fossil for scientific study or exhibition.

Q. What kind of tools do you use?

A. Hammers, chisels, miniature jackhammers, and an electric saw are among the tools initially used to chip away plaster and rock. Once the fossil has been exposed, we use dental tools, hardened steel pins, and tiny brushes for more delicate work.

Q. What happens when a fossil breaks?

A. Fossils are extremely fragile. We use special glue designed just for them.

Q. How do you know how to reassemble the animal?

A. Preparators use their knowledge of animal anatomy as a blueprint when working on a fossil. There are always clues in the bones—like evidence of muscle attachment—that help determine the posture of an animal. Other fossil clues may include teeth or skin imprints. If another specimen of the same animal is available, we can compare the bones and put them together based on that skeleton's information.

Q. How long does it take to become a preparator?

A. The basic techniques can be learned quickly, but it takes plenty of practice to become skilled. The most important quality is patience! Anatomy and paleontology can be studied in college, but preparation can only be learned on the job. A new preparator will start on low-quality fossils that have already been rejected from our scientific collections. Once scientists are confident in the quality of the preparator's work, he or she can progress to more delicate fossil material. Some of the best preparators have worked for 30 to 40 years.

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