On-site Raman and XRF analysis of Japanese/Chinese bronze/brass patina - the search for specific Raman signatures

The assignment of Asian bronzes and brasses is difficult because the copies of ancient pieces have been made a long time ago in different countries. A selection of 30 Japanese and/or Chinese bronzes/brasses are studied on-site in the storage and exhibition rooms of the Cernuschi Museum, in Paris, using portable Raman and X-ray fluorescence spectrometers. Attempts are made to identify specific Raman signatures of the patina to detect similarity in a nondestructive procedure. X-ray fluorescence measurements allow an identification of two brass artefacts and different types of bronze, including lead-rich and mixed leadtinzinc-rich compositions. The following phases are identified: CuO, Cu2O, Cu2S, tin oxides, ZnO, Cu3(OH)4SO4, Cu4(OH)6SO4, 3PbOPbSO4 H2O, PbSO4/PbO, Pb(AsO4)3Cl, HgO/HgS. Relics of the mould, retained as concretions at the artefact surface are also identified: TiO2, SiO2, and different soda(-lime) glasses. Patina with very similar colour and habit may have different Raman signatures. This study offers tools to classify the artefacts in a noninvasive way. Copyright (C) 2011 John Wiley & Sons, Ltd.