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 lead–tin–zinc‐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 © 2011 John Wiley & Sons, Ltd.