Monica Ganio

Roman glass across the Empire: an elemental and isotopic characterization

This study focuses on natron glass, dated from the 1st to 5th 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 (eNd between −2.5 and −6.0) for most of the samples. Conversely, samples with more negative eNd, 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.

The Sr–Nd isolation procedure for subsequent isotopic analysis using multi-collector ICP-mass spectrometry in the context of provenance studies on archaeological glass

Sr and Nd isotopic analysis of glass can be relied upon to unravel the provenance of the flux component and the sand used in the manufacturing of archaeological glasses, respectively. For a reliable isotopic analysis of the target elements using multi-collector ICP-mass spectrometry, the target elements need to be isolated from the matrix to permit adequate correction for instrumental mass discrimination. In this paper, a simple, fast and reliable analytical method for the isolation of Sr and Nd from complex sample matrixes such as archaeological glasses is proposed. Special attention is focused on the Nd isolation protocol, with the definition of TRU-Spec and Ln-Spec resin bed volumes and of an appropriate HCl concentration to optimize Nd elution from the column.

From lapis lazuli to ultramarine blue: investigating Cennino Cennini’s recipe using sulfur K-edge XANES

Abstract 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.

Investigation of an enameled glass mosque lamp: a 13th–14th-century Mamluk example or 19th-century European version?

AbstractBackground In this study, an enameled glass mosque lamp in the Brooklyn Museum collection is investigated to elucidate the origin and date of production of each of its components—the body, handles, wick-holder, and foot—to establish whether the lamp was produced during the Mamluk period (13th–14th century) or is a 19th-century European creation.ResultsUsing X-ray fluorescence spectrometry and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM–EDS), the body, handles, and wick-holder were found to exhibit identical composition. The lamp’s foot, however, presents a dissimilar composition, one significantly richer in sodium, magnesium, and potassium. The matrix compositions, colorants, and opacifiers of the body’s enamel decorations were characterized by SEM–EDS and Raman spectroscopy analyses and compared with Mamluk and 19th-century production.ConclusionsThe lamp’s body, handles, and wick-holder were produced using the same type of glass, one likely incorporating a plant ash flux typical of medieval Islamic glass. Materials composing the body’s enamel decorations are consistent with Mamluk production. The foot’s distinct composition indicates that it is a later addition to the object. Combining the analytical, stylistic, and historical evidences, this glass lamp can now be identified as a Mamluk example, one of few comprising an integral wick-holder. The presence of a wick-holder is discussed and connected to the small size of the lamp. Details informing understanding of the lamp’s manufacture are also included. The implications of these new findings on the object’s conservation treatment and display are discussed in the context of the upcoming reinstallation of the Arts of the Islamic World gallery at the Brooklyn Museum.Graphical abstractEnameled glass mosque lamp from the Brooklyn Museum collection investigated in this study (left image). Each colored enamel decoration (red, blue, white, yellow, and green) was studied as polished cross-sections. For example, microscopic and backscattered electron images of the blue enamel (center image) reveal the presence of rectangular inclusions. Raman spectrum of these inclusions (red spectra) exhibits identical Raman signature than lazurite (gray spectra) (right image)