X-rays ray tomography and aggregated analysis for Bavay treasure bronze statuettes analysis

摘要

X-ray imaging is one of the oldest techniques used in art analysis. X-Radiography is now completed with tomography.Used on bronze sculptures, it gives unrivalled information on state of conservation or fabrication process. Thetreasure of Bavay, discovered in 1969 in the north of France, is a hoard consisting of 371 bronze objects dated fromthe 1st to 3rd century AD. Among objects of various shape and use, an exceptional set of Roman statuettes wasdiscovered. Two Mercury statuettes were studied and, apart the fact that they are hollow, their characteristics arevery different. The metal walls are thin and even for the Lysippean Mercury and it could only have been made bythe indirect lost wax casting process. On the other hand, Indigenous Mercury still has its own inner refractory coremade of clay, whose shape is a very simple evocation of the statue. Here the direct lost-wax process was used, witha previous core shaping, on which wax was directly carved. In some cases, spatial information is difficult to read onflat 2D radiographies, so complementary images are made thanks to 3D tomography. Reconstruction algorithmsgenerate a 3D object issued from 720X-Ray images, showing the internal and the external surfaces. Virtual cuttingcan show any part of the object, allowing a detailed sight of the inner parts. For example, the Jupiter statue intomography shows on the inner surfaces metal infiltration and a secondary casting of a lead-tin. Further analysis canbe added to tomographic model: capturing the surface with a 3D scanner can add more precision on external surfacerepresentation: it was achieved for the Jupiter statue. In some cases also, photography for surface color information,or X-ray fluorescence chemical maps can also be placed on 3D models for a better localization of materiels.