Cities are places that connect things. Indeed, one of the chief virtues of life in cities is their ‘overwhelming communication advantage’, as urban geographer Peter J Taylor has remarked. Put simply, people in cities are better placed to tap into flows of materials and information, or to find the right associates to make complex tasks happen. This is equally true for the credit networks of Old Assyrian merchant colonies four millennia ago and the apprenticeship of watchmakers in 17th-century Geneva.
Today, this advantage is anchored in the material networks of railways, hyperways, and fibre-optic cables, but even the fortunes of Bronze Age cities relied heavily on their communication networks. Until recently, archaeologists often struggled to trace the details of urban connectivity in the past, but the steady development of scientific methods are pushing the boundaries of our knowledge. As biomolecular and isotopic methods turn materials like animal bones or metal fittings into evidence that can be tightly identified and provenanced, so too shifting patterns of past communication are coming into view.
A material that is currently transforming our understanding of past social networks is glass. One of the most striking archaeological showrooms for early glass products is Tell el-Amarna, which was founded in 1346 BC in Middle Egypt as a new capital for the heretic pharaoh Akhenaten and his powerful consort Nefertiti. This city proved a mirage, though, rising and then being deserted in less than 20 years. During that time, the site enjoyed an abundance of ‘stone that flows’: the Egyptian moniker for glass. Glass inlays were a convenient decoration when palaces and temples had to be fashioned from mud-brick on a lightning schedule.
In 2014, Anna K Hodgkinson of the Amarna Project led a detailed excavation in the workshop of one of Amarna’s glass bead-makers. Together with Miriam Bertram, she has been working since then to recreate the technology and production sequence employed by the Egyptian craftspeople. In a paper published in the 2020 Journal of Archaeological Science: Reports they chronicle their struggles and successes in learning the surprisingly intricate skills of a household industry.
Materials from the recent excavations must remain in Egypt, and Hodgkinson relies on portable on-site equipment for chemical examinations; yet she is able to trace the steps of the production process, including the addition of cobalt ore brought from the Western Desert as a colourant. From Amarna’s famous archives of royal letters, we know that some glass was brought to the site as diplomatic gifts from rulers in the Levant, the major glass-industry hub of the Bronze Age; but finds of large crucibles indicate that raw glass was also fused in Amarna, suggesting that much may still remain to be discovered in the years to come.
Recycling and big city life in Rome
The ongoing Danish-Italian project in Caesar’s Forum, Rome (CWA 113), has recently published a string of articles on glass from antiquity to the Renaissance. The glass finds in this urban excavation come from complex stratigraphies, which the archaeologists disentangle layer by layer. However, in Rome – as in many other places – these layers often overlap and intrude on each other. In this way, Rome is not only a palimpsest of urban phases, but also a mesh. We may not always be able to trace the exact development of the post-antique phases of Caesar’s Forum, due to the intense reuse of the space over time. However, the remains of the glass vessels, a commodity used in a variety of guises, such as table-ware, lamps, cosmetics, and medical containers, give us insights through their compositions into networks and economic patterns, as archaeologist Cristina Boschetti and the team are showing.
Published in Antiquity, Heritage Science and the Journal of Field Archaeology, the new results profoundly expand our knowledge of topics such as Renaissance trade, or the composition and recycling of Roman and late antique glass. We now know that glass recycling took place in Rome during the 1st century AD – earlier than hitherto known – and that this industry seems to have been highly organised. Later on, during the Renaissance, some glass finds have proven to be Tuscan imports, the first such wares to be found in Rome. This underlines the ongoing trade relations between regions in Italy during this period. All these things are markers of urban life and organisation, which are invisible to the eye, but become visible via a range of scientific analyses.
Urban life on the fringes of the Roman Empire
In Gerasa, an ancient city in modern northern Jordan (CWA 107), a Danish-German team has been conducting fieldwork for six years (2012-2017). The abundant glass finds have revealed another surprising view of networks, through analysis published in Nature: Scientific Reports, the Journal of Archaeological Science and Archaeometry. The unspectacular so-called North-west Quarter, where the finds were made, offers the highest ground within the Roman city walls. It looms above the monumental Sanctuary of Artemis, one of the Roman world’s largest sanctuaries.
The archaeology on the hill yields traces of use and reuse over centuries, not leaving many features in their original place. Yet the glass finds – those in both primary and secondary contexts – have yielded eye-opening results. Pioneering use of Hafnium-istotope ratios reveals which sorts of sand were used to produce glass. This has firmly situated the production of colourless glass in Egypt – settling a discussion that has been ongoing for decades. Furthermore, results have shown that intense recycling of glass was more likely to take place in locations that were not close to the coast, such as Gerasa. This is most likely because these places did not enjoy such easy access to glass as coastal locations, where the material was either imported by ship or produced.
Northern emporia and urban flows
While the use of glass expanded over the centuries to include the manufacture of vessels, window panes, and mosaic cubes, the early glass-bead industry never died. Far into the Middle Ages, glass-workers produced beads using techniques eerily similar to those employed 2,000 years earlier in Amarna. Glass-bead workshops producing colourful ‘Viking beads’ came to light a few years ago in the North Sea port at Ribe in Denmark (CWA 90). Geochemist Gry Barfod has now recreated the bead-makers’ recipes and traced their supply chains in a study that appeared last year in the journal Archaeological and Anthropological Sciences. She discovered that, despite the fabled seafaring skills of the Scandinavians, the supply networks were surprisingly slow-moving.
Ribe’s glass-workers did not source their raw material from contemporary glass-producers, who, in the 8th century AD, were still concentrated in Egypt and the Levant. Instead, the staple supply to the Ribe workshops was centuries-old glass, recycled from Roman wall mosaics and cullet retrieved from old Roman sites in Europe. By contrast, the level of know-how when handling this material seems surprising for a small trading port at the edge of the North Sea. Analysis revealed that craftspeople in Ribe did not simply melt and remake coloured glass splinters: they also knew how to alter its colour and opacity – putting skills to use that would have done credit to an Alexandrian alchemist a few centuries earlier.
Through the looking glass
Glass is a fascinating material in its own right: it is always in movement – liquid and changing – even if we cannot see it, and even on archaeological time-scales. It is fitting that it now provides us with an unprecedented lens to see urban patterns, flows of material, and networks across space and time. The links, the networks, the mechanisms, the technologies are pieced together with something as mundane and sometimes tiny as broken glass and smashed sherds – but, when analysed, they offer numerous ways of glimpsing past links: both the links that lasted and the links that broke.