Compositional Analysis of 14th–15th Century Enamels from the Altar of San Giovanni in Florence: an Integrated Study by Portable X‐Ray Fluorescence and Electron Probe Microanalysis

The enamels of the Altar of San Giovanni, from the Baptistery of Florence, were investigated using both non‐invasive and micro‐invasive analysis in order to elucidate the glass melting and colouring techniques. A few fragments detached from the altar and recovered by the restorers were analysed in cross‐section by electron probe microanalysis. Moreover, non‐invasive investigations by portable XRF allowed a large number of enamelled plaques to be investigated. The results showed a good agreement between the two techniques and made it possible to identify similarities or differences in the enamels of the three manufacturing periods of the altar.