An application of XRF and gamma-ray spectroscopy to the study of clay composition in Italian Renaissance ceramics

During the period spanning from the fourteenth to the sixteenth centuries, across the Italian peninsula, artistic workshops experimented with production of tin-glazed earthenware. This technique, partially inspired by imports from North Africa, the Middle East and Spain, included many regional specificities based on stylistic differences but also on the techniques and materials used. Based on the analysis of 15 fragments from the University of Urbino and the Warsaw National Museum, this study examines the clay’s compositional characteristics to determine the origins of the samples. The fragments, attributed on stylistic basis to the ceramics centres in Central Italy, namely Orvieto, Deruta, Pesaro, Faenza, and Viterbo were subjected to analysis utilizing two techniques: X-ray Fluorescence (XRF) and Radioactive Isotope Ratios measured with a High-Purity Germanium (HPGe) detector. The objectives were to discern the elemental composition of the clay and to group the samples based on their clay composition, thereby verifying their geographical provenance. Comparison of results from the HPGe detector and XRF analysis allowed for a com- prehensive evaluation of the elemental profiles, disclosing both similarities and differences among the samples. The findings set three clusters across both methods. Radioactive iso- topes analysis, employing decay data and statistical techniques such as hierarchical and K-Means clustering, consistently grouped samples into three clusters. Similarly, the XRF spectroscopy approach, incorporating Principal Component Analysis (PCA) and hierarchical clustering, showed three distinct clusters. Comparative analysis against the base data showcased impressive accuracy, with the radioactive isotopes and XRF method achieving around 73% and 65%, respectively. The Faenza cluster exhibited intricate compositions, where two samples attributed on stylis- tic basis to Pesaro (sample URB02) and Viterbo/ Orvieto (sample SZCMag3) consistently clustered with Faenza samples in both methods, despite differing geographical origins, sug- gesting similar elemental compositions and manufacturing processes. This raises inquiries about potential material exchange between regions, underlining the importance of consid- ering historical contexts in archaeological and provenance studies.