This study focuses on natron glass, dated from the 1^st to 5^th century AD, excavated in different areas of the Roman Empire. The eastern side of the Roman Empire is accounted for by three archaeological sites, Petra and Barsinia, both in Jordan, and Gonio, in Georgia. The Italian peninsula is represented by the Iulia Felix and Embiez shipwrecks, and by samples from Augusta Praetoria. Samples from Barcino in Spain are examples of the western side of the Empire, and the sites of Tienen and Oudenburg represent the northern provinces. No clear distinctions in glass composition and origin between the different regions of the Roman Empire can be made based on the major elemental compositions. However, the western, central and eastern Roman Empire samples can be divided into two groups, coloured and colourless, which also are reflected in the K₂O contents. Sr–Nd isotopes, used for provenancing geological raw materials in primary glass production, indicate an eastern Mediterranean origin (εNd between −2.5 and −6.0) for most of the samples. Conversely, samples with more negative εNd, between −7.02 and −10.8, indicate a western Mediterranean origin. By applying this technique on samples from well known archaeological contexts, this study demonstrates that several primary glass factories were located throughout the Roman Empire. This is in contrast with current interpretations of late Roman to early Byzantine data.

As one of the most desired and expensive artists’ materials throughout history, there has long been interest in studying natural lapis lazuli. The traditional method of extracting the blue component, lazurite, from lapis lazuli, as outlined in Cennini’s Il Libro dell’Arte, involves a lengthy purification process: (1) finely grind the rock; (2) mix with pine rosin, gum mastic, and beeswax; (3) massage in water to collect the lazurite. Repeating the process produces several grades of the pigment, typically referred to as ultramarine blue. Here, we investigate the sulfur environment within the aluminosilicate framework of lazurite during its extraction from lapis lazuli. The sulfur XANES fingerprint from samples taken at the different stages in Cennini’s extraction method were examined. All spectra contain a strong absorption peak at 2483 eV, attributable to sulfate present in the lazurite structure. However, intensity variations appear in the broad envelope of peaks between 2470 and 2475 eV and the pre-peak at 2469.1 eV, indicating a variation in the content of trisulfur (S₃ ⁻˙) radicals. By studying the effect of each step of Cennini’s process, this study elucidates the changes occurring during the extraction and the variability within different grades of the precious coloring material. The increasing application of XANES to the study of artist’s materials and works of art motivated extending the research to assess the possibility of X-ray induced damage. Direct comparison of micro-focused and unfocused beam experiments suggests an increase of the S₃ ⁻˙ radicals with prolonged exposure. Analysis indicates that induced damage follows first-order kinetics, providing a first assessment on the acceptable amount of radiation exposure to define the optimal acquisition parameters to allow safe analyses of lapis lazuli and ultramarine pigments.