Large amounts of work have been done on Roman glass, largely in relation to Roman glass vessels. The main focus of research I have seen lies in identifying the source material of the glass through chemical composition and to determine the infrastructure of the industry.
Much Roman material (and many other European style glass) tends to be in the form of mosaic glass. Mosaic glass is made when the craftsman fuses canes of variously colored glass to form a pattern. This can be fairly simple, like checkers or swirls, but can also be much more complicated, like eyes or flowers. Another mosaic technique wraps glass of various colors around a central rod of glass, creating swirls. Both these chunks are then sliced to create sheets of the desired pattern.
Roman glass has a wide range of forms, from goblets, chalices and cups to bottles, flasks, bowls, plates, and even windows and tesserae. Interestingly, I have found very few resources looking at Roman glass beads. This is understandable on the one hand, given the range and prevalence of Roman glass vessels. On the other hand, I’m either missing a large chuck of sources or there is a large gap in archaeological knowledge of Roman beads.
When speaking of Roman material, we must remember that the Roman Empire held a wide range of territory for a long period of time. Most studies focus on Rome’s European territories, particularly those in Italy and Britain. Most studies also focus on the first through fifth centuries AD, the height of the Western Roman Empire into it’s decline.
The Romans were highly influential when it came to glass technology. The blowpipe was first invented in Rome, paving the way for blown glass up through modern times. The mosaic technique is also often seen as Roman, though there is evidence for it in Southeast Asia.
The most striking aspect of glass research in Rome, however, is the chemistry of the glass created throughout the empire. Prior to the formation of the Roman Empire, glass in Egypt, the Middle East, and other parts of Europe was a silica-soda-lime glass that used a plant source of soda (i.e. plant-ash). Yet, Roman glass instead uses a mineral soda source (e.g. shell or limestone). Researchers have pinpointed this mineral source to natron, found at Wadi Natrun in Egypt. It seems that Rome was using ingredients from across the empire to make their glass, which is also evidenced by the very small number of silica-sand sources they used. Interestingly, as the Roman empire declined, so did the use of natron in glass. By the end of the 7th century, most glass-making sites switched back to using a plant-ash source of soda, probably due to a lack of infrastructure to transport natron from Egypt to the manufacture sites.
It is also important to note the relative homogeneity of Roman glass when compared with glass types from various parts of Africa and Asia. Roman and other European glass belongs to the general m-Na-Ca or v-Na-Ca forms, whereas parts of Asia can have all of the general glass types mentioned in my discussion on chemistry. The reasons for this are uncertain, but it is something to keep in mind.
Another important piece of information from all this research lies in the infrastructure of glass craftsmanship. There are far more written sources for Rome than many other places, and there has been far more work done on Roman sites than elsewhere, so the data is plentiful. The system, then, for glass manufacture and working in Rome is generally seen as follows: Raw materials for glass manufacture were acquired and shipped to a specific number of glass manufacturers. Those primary workshops made glass in bulk and shipped that to many smaller, secondary workshops who would turn the glass into finished products The finished products were then largely taken by merchants to various parts of the empire. This is highly important, because it requires a certain amount of infrastructure in order to function. If the raw materials cannot be acquired or transported, the manufacturer’s will have to adapt (as we see with the shift in chemistry after the decline of the empire).
Recycling is also a common theme in the literature, as it was a common practice in most of the world. Glass is difficult to make and requires very specific ingredients, so naturally if some glass breaks, people would try to reuse it in some way. This occurred largely by sorting the glass by color and then melting it down again to create new objects. In Rome, this would generally happen at the glass working sites, since remelting glass is not nearly as complex as making it.
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