© T. SEVERIN-FABIANI / M. THOURY / L. BERTRAND / B. MILLE / IPANEMA CNRS MCC UVSQ / Synchrotron SOLEIL / C2RMF CNRS Photothèque
Comparison of images using high spatial dynamics-photoluminescence (PL, top) and optical microscopy (bottom). The picture shows a section of one of the spokes of the Mehrgarh amulet, a copper object from the ancient Chalcolithic period found in the 1980s in present-day Pakistan. The PL image shows a rod eutectic structure, invisible using any other technique tested. The secret of its manufacture has been revealed thanks to a new approach using UV/visible photoluminescence spectral imaging implemented by the Soleil synchrotron. This amulet is the oldest known object made using the lost wax process. This process uses a model sculpted in a material such as beeswax, which is then encased in clay. Wax melts at low temperatures so it runs out easily when the clay is heated. Molten metal is then poured into the empty clay mould, taking the place of the wax.
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