Preparation and conservation of bones

The key work follows in the laboratory, where the fossils are made ready for study or for exhibition. There are now many professional palaeontology preparators and conservators, and the techniques available have advanced enormously in recent years. The important point to remember is that information is lost at every stage in the process of excavation and preparation, and the good technician seeks to minimize that loss.

Back in the laboratory, the plaster jackets are cut off the large bones, and the difficult job of preparation begins. The general idea of preparation is to remove the sediment from the bones so that they may be studied. Conservation includes the treatments applied to bones so that they may be handled and stored without fear of damage. A variety of hand-held chisels, needles, mechanical drills, and brushes may be used to remove the sediment (Figure 2.3(a)). Airbrasive treatment may be applied, a system that blows fine abrasives in a focused blast of air at the specimen. If the bones are contained in limestone, then the blocks may be soaked in dilute buffered acetic or formic acid to remove the sediment. This technique can produce spectacular results, as there is no risk of mechanical damage to the bones, although there is a risk that mineralized traces of other, non-skeletal, tissues may be etched away.

The bones are generally strengthened by coatings of synthetic compounds that are readily soluble in acetone or alcohol. These consolidants have replaced the rather crude glues and varnishes that were used in the past, all of which suffer from problems of decay, and that cannot be removed readily to allow further cleaning and preparation. Much of the work in a museum laboratory is also concerned with conserving the fossils that were collected long ago, and that fall apart as a result of chemical changes in the bone and sediment.

Specimens of fossil vertebrates preserved on slabs are usually prepared mechanically, and the skeleton may be left on the slab, as the sediments provide a stable support. Sediment with small bones and teeth, mi-crovertebrate remains, is processed in the laboratory in various ways to extract the fossils. If the enclosing sediment is limestone, then acid treatment is effective. If the sediment is unconsolidated, then simple washing and sieving may be enough to extract the bones (Figure 2.3(b)).

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