Federico Carò

A group of copper-based artifacts in the collection of the Metropolitan Museum of Art, lacking clear archaeological provenance, has been attributed to early and pre-modern Islamic Iran based on their stylistic features and forms. To gain insight into the materials and metalworking techniques used in their production, these artifacts were subjected to microanalytical investigation. A non-invasive micro-XRF technique was employed to characterize the alloy composition of the artifacts and their decorative inlays. Additionally, the microstructure of a selected group of artifacts was examined using scanning electron microscopy–energy dispersive X-ray spectroscopy, and metallography techniques. The results revealed that the artifacts were produced with a range of copper-based alloys, including leaded ternary (Cu-Zn-Sn-Pb), high-tin bronze, and brass. The inlays consisted of silver (alloyed with copper), impure copper, and alloyed gold. The leaded ternary artifacts exhibited a cored cast microstructure with evidence of cold-working and numerous large lead globules, while the tin bronze and brass artifacts displayed signs of the thermo-mechanical operations used to shape them. Based on these findings, Iranian copper-based metalworking in the Islamic period is shown to have employed a variety of compositions as well as a range of shaping and decorative techniques.

A group of metal objects excavated at Qasr-e Abu Nasr in south-central Iran in the 1930s, now in the collection of the Metropolitan Museum of Art, has been analyzed to examine metalworking techniques and metallurgical processes. Thirty-three objects were studied and analyzed by micro-X-ray fluorescence, scanning electron microscopy-energy dispersive X-ray spectroscopy, and metallography techniques. The results of these analyses show a wide range of copper alloy compositions including impure copper, tin bronze, brass, leaded tin bronze, leaded brass and leaded ternary Cu-Sn-Zn (gunmetal) alloys. Also, two silver-copper and one pewter object were identified among the analyzed objects. The results of this interdisciplinary study provide new insights onto the archaeology of Qasr-e Abu Nasr, as well as present new information about the history and evolution of copper-base metallurgy on the Iranian Plateau during the Sasanian and early Islamic periods.

Angkor’s stone material culture has survived the effects of time and constitutes an essential corpus of evidence whose study holds the key to a better

Polychromy in Ancient Greek Sculpture was the subject of the exhibition Chroma: Ancient Greek Sculpture in Color, held at The Metropolitan Museum of Art (The Met), New York, in 2022–2023. On this occasion, a multidisciplinary project involving The Met’s Departments of Greek and Roman Art, Objects Conservation, Imaging, Scientific Research, and colleagues from the Liebieghaus Polychromy Research Project in Frankfurt, Germany, was carried out to study an Attic funerary monument. The color decoration of the sphinx was reconstructed by combining non-invasive and minimally invasive techniques that provided information about surviving and lost pigments, original design, and painting technique. Results of multiband imaging, digital microscopy, and X-ray fluorescence spectroscopy guided the removal of minute samples from selected areas for examination by Raman spectroscopy and scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy, to shed light on the pigments and paint stratigraphy. The color palette included two varieties of blue, Egyptian blue and azurite, a carbon-based black pigment, two reds, cinnabar and red ocher, and yellow ocher, all painted directly over the marble without a preparation layer. The scientific findings informed the physical reconstruction of the sphinx made by archaeologists from the Liebieghaus Polychromy Research Project, featured in the exhibition.

Among the holdings of the Solomon R. Guggenheim Foundation, New York, is a large-scale portrait by Édouard Manet that remained apparently unfinished upon the artist’s death, in April 1883. This work, now known as Woman in Striped Dress, belongs to Manet’s late artistic production and dates from around 1877 to 1880. A collaborative endeavor entailing archival research and scientific analysis revealed that the composition had suffered dramatic alterations prior to its arrival at the museum in 1965 as an extended loan, likely carried out to “finish” the picture in order that it would be marketable and to increase its sale value. Among the main changes explored in this technical study are the reductions in the canvas size and subsequent varnishing campaigns. Furthermore, along with a detailed characterization of the original materials present in the ground and paint layers, this research contributed to the identification of posthumous retouchings, possibly executed concurrently with trimming the canvas along both sides and at the top edge. The investigation was instrumental in devising an appropriate treatment to remove the discolored varnish and select areas of retouching, which obscured significant details of the composition and Manet’s delicate brushwork.

The nature of ground preparations is of critical interest to those engaging in the study of historical painting techniques, as certain materials can be identified with specific regions and school of painting. This is the case of a particular ash-based, calcite-rich material obtained as a byproduct of lye production, recently identified for the first time in ground preparations by means of chemical analysis, and which is considered specific to Baroque artists of Spanish school. Because of limitations in the size of the samples that can be removed from works of art, and because of the intrinsic variability of ash composition, chemical analysis alone may not be representative of the whole ash-containing layer, thus limiting the identification of this material. By comparing the morphology, texture and composition of calcite pseudomorphs in laboratory ash to the ground preparations in three Baroque paintings, we provide additional, unequivocal tools to identify calcite particles from ashes in paint cross sections. The results demonstrate that the chemical composition of the ash can vary, but that the morphology and size of the calcite pseudomorph crystals abundantly present in the recycled ash applied to the canvas supports are consistent and extremely characteristic. The unique polygonal shapes and skeletal morphology of the pseudomorphs and their abundance make them ideal markers to recognize ash in paintings’ ground layers, even when very limited amounts of sample are available. The study shows also that the practice of using recycled ash in the preparation of ground layers occurred outside Spain, by artists with direct or indirect Spanish lineage.

The scientific investigation of works of art has an essential role in understanding museum collections and is fundamental in establishing successful conservation and restoration strategies. In the multidisciplinary environment of museums, scientists work with conservators and curators not only to more profoundly understand works of art but to better preserve them, and this often involves using analytical techniques borrowed from different disciplines of Earth sciences (e.g. mineralogy, geochemistry, and petrology). Two case studies – the stones of Angkor (Cambodia) and a blue paint mineral pigment – demonstrate how the Earth sciences are helping to identify, determine provenance, and conserve a broad spectrum of works of art. The impact on archaeological and art historical scholarship is substantial