Evaluation of Quantitative XRF Analysis Applied to Determine Cobalt Sources in Chinese Blue-and-White Porcelain

A method using the ratios between MnO, Fe2O3 and CoO to differentiate the cobalt sources for Chinese blue-and-white porcelain was developed in Oxford in the 1950s using X-ray fluorescence (XRF) analysis directly on the glaze. In this paper, six blue-and-white porcelain sherds from the Luomaqiao kiln were analysed by XRF on the glaze and by scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) in cross-section. The ratios between MnO, Fe2O3 and CoO calculated by quantitative XRF and EDS analyses are different. The analysis depths for MnO, Fe2O3 and CoO are < 60 mu m by XRF analysis. However, the average glaze thickness of samples is > 400 mu m, and the MnO, Fe2O3 and CoO mainly remain in the lower layer of the glaze, which is beyond the analysis depths of XRF analysis. The limitations of major and minor quantitative analyses for differentiating cobalt sources are discussed.