Glass in ancient Rome was considered a very valuable commodity that is available only to the extremely wealthy. The material was also produced in small sizes not for practical but for cosmetic purposes until the introduction of glass blowing. However, despite prominence and long life of the Roman glass, there remains limited information about their glass industry itself, their glassworkers, or where it comes from. Researchers have also long debated where the transparent glass was made, particularly Rome’s finest “Alexandrian.”
Rome’s glass industry and their finest “Alexandrian”
Many archeologists interpreted the name Alexandrian as a sign of its Egyptian origins but it remains ambiguous. Recently, a team of researchers from Aarhus University in Denmark has traced the origins of the finest glass to Egypt. Based on the rare element hafnium (Hf) isotopes found within the glass, researchers solved the long-standing mystery.
In their study, which appeared in journal Nature, Geoscientist Gry H. Barfod and the team explained that they confirm that they analyzed 37 glass fragments at the archeological site in northern Jordan. Included in the said fragments were an Alexandrian glass, a glass made more recently either in the Levant or in Egypt, and manganese-processed glass.
There were previous studies that compared Alexandrian glass and manganese glass produced in the Levant but they failed to differentiate the samples as they contained the same ratios of isotopes (a variant of a particular chemical element) neodymium and strontium. For their study, Barfod and her team looked into the relative ratios of isotopes of the hafnium element instead of neodymium and strontium.
Their analysis shows that ratios of hafnium can be used to differentiate Levantine glass from Alexandrian glass that is decolorized with manganese. They said that the Roman glass industry underwent a massive expansion in the first century CE. At its peak, it supplied not just tableware for households in the Empire but also provided materials for major public buildings with tonnes of glass for mosaics and windows.
The researchers also share that Alexandrian glass contains hafnium ratios that are comparable to the glass known to be made in Egypt. It appears that their findings settle the longstanding mystery that Alexandrian glass does indeed come from Egypt.
Using hafnium isotopes in determining the origins of materials
Co-author Ian Freestone, who is also an archeologist at the University College of London, shared via Smithsonian Magazine that their study clearly shows the potential of hafnium in clarifying the origins of the early materials. He also predicts that the hafnium isotopes will become a significant part of the scientific toolkit in their study of the ancient economy.
Testing the chemical makeup of the sand will be the researcher's next step to know if ratios found in the glass samples also match with grains on local beaches in the Levant and Egypt. “It’s been a mystery that historians have dreamed of solving, Dr. Barfod said.
New York Times’ Katherine Kornei, who was not involved in the study, shared that glass forced in different geographic regions also have different hafnium signatures. This was explained by the researchers from Aarhus University. They said that Egyptian glass consistently contains more of such elements and had lower isotopic ratios compared to glass produced in the Levant. After the sand is expelled from the Nile, it sweeps east and then north up the coast of the Levant. Then, it will be moved by water currents and the zircon crystals within the sand are heavy so they settle early on the Egyptian beaches. This is also the reason why glasses forged in Egyptian furnaces contain more hafnium than Levantine glass.
Dr. Barfod finds it rewarding to pin down the origin of the ancient Rome’s finest glass as it has been an open question for decades. Yet, it is still a mystery to them why glasses from the Levant and Egypt have different hafnium isotopes ratios. One possibility the researchers can think of is that the zircons have certain isotopic rations that are bulkier, denser, and bigger that affect their movement. The team added that it would be logical to analyze the chemistry of Levantine and Egyptian beach sand to confirm their findings. Then, the next step is to go out and set sand from these places.
The four main product categories of the glass industry include glass containers, products made from purchased glass, blown or pressed glass, and flat glass. Over the five years to 2020, the industry in the US is expected to increase at an annualized rate of 0.1% to $28.1 billion with a forecast decline of 0.3% this year. This is according to IBIS World. The biggest opportunity for growth of the industry is that basic flat glass is processed for various uses in construction and building, including glass bricks, glass wall panels, windows, mirrors, shower screens, and doors.
It is the housing market in the US that generates a significant demand for flat glass. Meanwhile, the annual turnover of the glass industry in Italy amounted to €6.1 billion in 2017. If detail it by sector, the revenue for the manufacture of hollow glass amounted to €2.57 billion, for the shaping and processing of flat glass was $1.7 billion, for the manufacture and processing of other glass, including technical glassware, was €912 million, for the manufacture of glass was €743 million, and for the manufacture of glass fibers were €150 million revenue. This is based on a survey conducted by Statista.
Glassmaking did not originate from the craftsmen in the Roman Empire, just like other technological advances in the Roman world. Instead, many advances during that period were made when the art form was fused within its borders. However, the establishment of any commodity, whether for necessity or luxury, flourished within the ancient Roman Empire as their population has the resources to use and develop any existing technology. Ancient Roman history site UNRV, for instance, shared that glassmakers thrived in Rome and other parts of Italy during the reign of Emperor Augustus. Forming glass would then be considered primitive by later techniques used in the empire, such as using molds.
The findings of Aarhus University researchers help us better understand not just the important aspects of the ancient glass industry but their ancient economies and the movement of goods as well.