is applied. The lacquer will penetrate the bone and other organic remains, but not the shale itself, as shale is impenetrable to watery solutions. When the lacquer has set, a frame of modelling clay is built on the rock face around the fossil. A two-component epoxy is poured onto the frame, forming the new artificial surface for the fossil. The composition of the resin is important, as it will have to soak into the fossil to further strengthen it and to bind it to the new surface. This can be controlled by varying the resin viscosity. When the epoxy has set, the slab is turned over, and preparation begins from the shale at the back. Layer by layer of oil-shale is removed with brush and scalpel. When the preparator hits the fossil, more lacquer and glue is applied to further stabilize the fragile fossil. When the work is done, all traces of oil-shale have been removed, only the fossil itself remains on the epoxy slab. The contrasting physical property of the rock and fossil are essential for this technique to succeed. The organic remains of the fossil are porous and hygroscopic, while the oil-containing rock is not. Thus, the lacquer can penetrate fossils, and not rock, enabling the preparator to “glue” the fossil to the artificial slab, without at the same time gluing it to the shale. References Fossil preparation Paleontology Geology