RESUMO
The combined use of non-invasive on-site portable techniques, Raman microscopy, and X-ray fluorescence spectroscopy on seven imperial bowls and two decorated dishes, attributed to the reigns of the Kangxi, Yongzheng, Qianlong, and Daoguang emperors (Qing Dynasty), allows the identification of the coloring agents/opacifiers and composition types of the glazes and painted enamels. Particular attention is paid to the analysis of the elements used in the (blue) marks and those found in the blue, yellow, red, and honey/gilded backgrounds on which, or in reserve, a floral motif is principally drawn. The honey-colored background is made with gold nanoparticles associated with a lead- and arsenic-based flux. One of the red backgrounds is also based on gold nanoparticles, the second containing copper nanoparticles, both in lead-based silicate enamels like the blue and yellow backgrounds. Tin and arsenic are observed, but cassiterite (SnO2) is clearly observed in one of the painted decors (dish) and in A676 yellow, whereas lead (calcium/potassium) arsenate is identified in most of the enamels. Yellow color is achieved with Pb-Sn-Sb pyrochlore (Naples yellow) with various Sb contents, although green color is mainly based on lead-tin oxide mixed with blue enamel. The technical solutions appear very different from one object to another, which leads one to think that each bowl is really a unique object and not an item produced in small series. The visual examination of some marks shows that they were made in overglaze (A608, A616, A630, A672). It is obvious that different types of cobalt sources were used for the imprinting of the marks: cobalt rich in manganese for bowl A615 (Yongzheng reign), cobalt rich in arsenic for bowl A613 (but not the blue mark), cobalt with copper (A616), and cobalt rich in arsenic and copper (A672). Thus, we have a variety of cobalt sources/mixtures. The high purity of cobalt used for A677 bowl indicates a production after ~1830-1850.
RESUMO
Almost all archaeometric studies on Chinese ceramics are carried out on the excavation materials. Therefore, a detailed, comparable database that defines different workshops and production periods already exists. But the masterpieces preserved at museums, art galleries, and/or private collections, which are artistically considered as genuine artifacts, also require similar scientific investigations to define their provenance and authenticity. The research on artworks is only possible with the use of portable, noninvasive techniques that are developing daily concerning their capability of detection limits, rate of measurement, and ease of use. In this study, the results obtained with a handheld X-ray fluorescence (XRF) (also called portable XRF) and wavelength dispersive XRF instrument were compared to evidence the efficiency and drawbacks of the portable model. To achieve this goal, 12 sherds, which represent blue-and-white porcelains of Yuan and Ming Dynasties (China), were analyzed and the chemical composition of the body, glaze, and blue decor were identified. The comparison of the results with the measurements carried out on the excavation materials, which are produced in both southern and northern China, revealed the authenticity of the artifacts. Even sodium cannot be detected with portable XRF, the distinction of different production centers is possible with the detection of major (Mg, Al, Si, K, Ca), minor (Fe, Ti), and trace elements (Zr, Sr, Rb).
