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Conservators at the Natural History Museum were asked to prepare a number of specimens for display in a new exhibit entitled What on Earth? Several specimens, including the Green Sea Turtle pictured above, required conservation treatment in order to make them stable and appear complete. The turtle is particularly significant because it represents a species which is now endangered.
Condition concerns. The turtle came to the Conservation Lab missing a small portion of its shell, called a scute (these are protective plates composed of keratin — the same protein that’s in your hair and nails). After discussions with the Herpetology Collections Managers, it was decided that the missing area should be reconstructed. A treatment plan was devised so that the restoration would be easily reversible. Another criterion was that the restoration would not be visible from a normal viewing distance, but would be readily apparent upon close inspection.
Toned epoxy for reconstructing the missing area of the turtle shell.
Treatment. The missing area of the scute was modeled in clay and then a silicone rubber mold was created from the clay form. A clear epoxy known for its long-term stability was selected as the casting material. The epoxy was toned with dyes to match the amber color of the shell and was then poured into the mold. After a few hours of curing, a small amount of deep reddish-brown epoxy was added to the mold in order to match the mottled pattern of the shell. The epoxy was left to fully cure for about a week. The cast was then removed from the mold and polished to match the sheen of the original shell. Finally, the new scute was attached to the turtle using a stable, reversible adhesive (see after treatment image below, on right).
Before treatment, detail of missing area. After treatment, detail of reversible epoxy fill.
Check out the turtle for yourself in our exhibit What on Earth?