Non-Invasive On-Site XRF and Raman Classification and Dating of Ancient Ceramics: Application to 18th and 19th Century Meissen Porcelain (Saxony) and Comparison with Chinese Porcelain

The authentication and dating of rare ceramics is generally carried out using subjective criteria, mainly based on visual interpretation. However, the scientific study and evaluation of the materials used could contribute objectively. The analytical data relating to the major and minor elements of the coloring agents of the decoration or the base marks, and the characteristics of the raw materials (related to geology and ore processing), can be obtained on the conservation site non-invasively using a pXRF instrument and the phases formed may be identified using Raman microspectroscopy. This approach is applied to 28 objects assigned to the production of the Meissen Factory, from the collection of the Musée National de Céramique, Cité de la Céramique, Sèvres. They have polychromic or blue-and-white decorations and are supposed to have been produced in the 18th and 19th centuries. Some have a production date that has been perfectly established, others may have been produced using an earlier mold, or even have been decorated on an unknown date different from that of the firing of the biscuit. The combination of several classification criteria concerning the type of glaze, previously identified in the study of French and Chinese 17th and 18th centuries productions, i.e., the elements associated with cobalt present in the mark or the blue decoration and the relative levels of impurities of the glaze matrix, both characteristic of the raw materials and giving a strong XRF signal, leads to the identification of groups of homogeneous objects (respectively, counting seven, three, two and two objects for which at least four out of five criteria are identical); the other objects present too many differences to be considered as having been produced with the same raw materials. The first group brings together almost all the objects with a reliable pedigree made before ~1750, but includes two objects with decoration types closer to those of the 1800s. The comparison of the pXRF signals confirms the possibility of identifying the use of European ingredients for the production of painted enamels in the Qing dynasty.