Transfer technique

The transfer technique is a technique to stabilise and prepare fossils by partially embedding them in plastic resins (i.e. epoxy or polyester) in order to preserve the position of the preserved fossil once all of the rock matrix is subsequently removed. Notable examples of this technique are fossils preserved in oil shale (such as those from the Messel Pit) or other substrates that will deteriorate under atmospheric conditions, or fossils preserved in acid-soluble carbonates (such as fossils from the Santana Formation). The technique is notable for delivering exquisite preparations of both very high scientific and display value.

The method was pioneered by Harry Toombs and A.E. Rixon of the British Museum in 1950 with the introduction of the technique as a means of extracting fish fossils from acid-soluble carbonates. The technique permitted the preparation of delicate, fragmented, or otherwise unstable fossils by the removal of virtually all of the surrounding rock matrix. The resulting preparation retains the position of all of the parts of the fossil in the position in which they were preserved in the fossil. While the method developed by Toombs and Rixon calls for plastic resins, other substances, such as a mix of ground chalk and beeswax have been used.

While the original method was developed to deal with fossils freed from the matrix by acid, its most well known application is to the fossils from The Messel pit. These fossils, noted for their exquisite preservation, including soft tissue, body outline and even colour sheen on beetle wings, are notoriously difficult to preserve. The fossils themselves are flat, sometimes film-like on the surface of the rock layers. The oil shale contains 40% water. When a slab is broken free of surrounding rock, it will soon dry out and crack. A slab with a perfect fossil will turn to a heap of rubble in a few hours, destroying the fossil with it. This was the fate of numerous Messel fossils until the transfer technique was started to be applied in the 1970s.

In order to preserve the fossils once their slab is taken out of the rock, the fossil need to be transferred from the rock surface on to a durable, artificial surface. The water in the fossil itself also needs to be replaced.

As soon as the slab bearing the fossil is worked free from the rock, it is submerged in water to stop it from cracking. This involves packing it in plastic and sometimes wet newspaper. While in the wet state, it is cleaned up and all preparation needed for the transfer conducted.

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