On Scientific Reports, a collaborative study between IIT, Ca’ Foscari University, and INFN-CHNet
In Roman times, glass was colored using metal powders. This technique, passed down as an oral tradition by glassmakers, is now documented by a scientific study that analyzed two rare spherical metal artifacts found embedded in glass fragments during an archaeological survey in Aquileia.
The study, published in the prestigious journal Scientific Reports, was conducted by researchers from the Center for Cultural Heritage Technology (CCHT) at the Italian Institute of Technology (IIT), in collaboration with the Department of Molecular Sciences and Nanosystems at Ca’ Foscari University in Venice and the INFN-CHNet node in Bologna with the University of Bologna.
“Understanding the technology of Roman glass, discovering new details about coloring techniques and production processes, is not only valuable from a historical and archaeological perspective,” emphasizes Arianna Traviglia, Director of CCHT@Ca’Foscari at IIT. “These results can also be inspiring and interesting for the study, processing, and production of contemporary glass.”
Despite its ancient tradition, glass technology is continuously evolving. Studying the chemical and physical characteristics of glass and understanding how production processes influence its final properties has led to the creation of increasingly high-performance glasses for various applications, from the pharmaceutical sector to electronics. For example, glass technology enables the development of increasingly advanced optical fibers.
“Inside Roman glass waste, we noticed two almost perfectly spherical objects. The uniqueness of these artifacts prompted us to conduct an in-depth study,” explain Francesca Di Turo and Alessia Artesani, researchers at CCHT@Ca’Foscari at IIT who led the scientific analyses.
“From these observations, we had the need to understand what material they were made of and what the structure of these spheres was (e.g. solid or hollow). Indeed, by understanding in detail the structure and composition of these residues in the glass, we could clarify their origin,” explains Giulia Moro, a doctoral student at the Department of Molecular Sciences and Nanosystems at Ca’ Foscari University.
The glass production technology in Roman times was highly advanced, and the methods of glass coloring using metals were diverse, with some still not fully understood.
The researchers used various analytical techniques to study these spheres, including electron microscopy, electrochemical analysis, and X-ray tomography. Optical microscopy revealed the heterogeneous nature of the metals present in the spheres, which were then identified through electrochemical techniques and elemental analysis.
“Electron microscopy allowed us to detect traces of glass inside the spheres, clear evidence that they formed during the glass production stages,” say the researchers. X-ray tomography, on the other hand, allowed a direct look inside one of the spheres, revealing its structure without damaging the archaeological artifact.
The investigation results clarified the process that led to their formation and made it evident that the presence of these leaded bronze objects is related to ancient glass coloring methods. Indeed, since ancient times, metal flakes and powders, waste products from other processes, were used to give intense and brilliant colors to glass. An example is the use of bronze to achieve green-blue shades, which was widespread in Roman times.
“Studies like this emphasize the value of a multi-analytical approach in the study of Cultural Heritage and suggest the importance of cultivating interdisciplinary networks,” says Ligia Maria Moretto, professor of Analytical Chemistry and co-author of the article. “In this case, the collaboration between IIT and Ca’ Foscari has allowed the full synergy of chemical, physical, and archaeological expertise.“
