Glass Manufacture in Roman Yorkshire
For a much more complete overview of roman glassmaking in Yorkshire and the north, a download of ‘Broken bottles and quartz-sand : glass production in Yorkshire and the North in the Roman period.’ (published in Aspects of Industry in Roman Yorkshire and the North. Oxford 2002: Oxbow Books, pp. 81-93) by Jennifer Price, is available from Durham University.
Glass working is known to have taken place in virtually every part of the Roman world, yet the evidence for glass production is often difficult to identify and interpret. Literary, epigraphic and iconographic evidence is rare, and just about non-existent in Britain. The products of this illusory industry are, fortunately, much better known, and range from simple glass beads to exquisite tableware. Click on the images in the panel to the right for examples.
Glass production can be categorised into two phases, primary and secondary production, which need not take place in the same geographical location.
Primary production is the creation of the glass from the raw materials. the
Former, which in the Roman period was quartz sand
Flux; Soda was added to lower the melting. However soda, in the form of “natron” a mineral found in dry lake beds, was difficult to obtain, the primary sources known to the Romans being in Egypt (especially the Wadi Natrun) and possibly one site in Italy.
Stabiliser; glass formed of just silica and soda is naturally soluble, so a stabiliser, usually either lime or magnesia is added.
Colour arose from natural impurities, iron oxide causing the most common blue-green colour, and could be changed by deliberately adding other minerals
Very few sites of primary production have been identified across the empire, the majority being in the East Mediterranean, presumable because they were close to the source of soda. These sites utilised large specialised furnaces containing tanks which were capable of producing many tonnes of raw glass in a single furnace firing (which might have taken weeks). The glass block found at Bet She’arim in lower Galilee, is estimated to have weighed 8 tonnes, although this may be a post-Roman example. The glass blocks could then be broken up and exported around Europe, possibly being used as ballast for ships. However, a single primary production site is known in Britain, and it is (of course!) in Coppergate, York, although here things were on an altogether smaller scale. The Coppergate site revealed fragments of pottery Ebor ware vessels used as crucibles with rim diameters of between 9 and 15 inches( 0.22m and 0.38m) which bear evidence that the raw materials had been used to make glass, rather than simply melting imported glass.
In contrast to glassmaking, glassworking sites have been found across the Roman world, although evidence is often scant. Furnaces and annealing ovens are sometimes found, although these structures were often very small and little more than ground plans usually remain, indeed, most of our current knowledge comes from representations on two Roman oil lamps, showing a low domed furnace with two apertures. In 2005/6 Mark Taylor and David Hill embarked on an experimental project in Hampshire to re-create Roman glassworking furnaces and ovens, their website detailing their experimental archaeology can be found here.
Whilst it is likely that manufactured glass products were imported into the area, and possibly into Britain, it is certain that secondary production took place here. Working of glass requires significantly lower temperatures and substantially less fuel than primary production making it easier, although evidence is known from just a few sites in York, from the vicus at Castleford, and possibly from an Iron Age – early Roman settlement at Roxby, on the North York Moors. It seems unlikely that this paucity of evidence represents a true picture of Roman glassworking in Yorkshire. By AD 100, Roman innovations in the glass industry had made glass widely obtainable, relatively inexpensive, and no longer reserved for the elite, indeeed, glass vessels have been found in virtually all Roman settlement sites, both as tableware and as containers for liquids, cosmetics, foodstuffs etc. The Roman army will have needed window glass, at least for the high status buildings, so it seems likely that the army would have been involved in glass production in some way, possibly evidenced by the Coppergate site being within the canabae (civilian settlement adjacent to a Roman fort housing military dependents and civilian contractors) of the fortress. Also, the high costs of transporting such fragile goods would suggest the high probablity of most glass production being on relatively small local sites, close to the point of consumption.
The Roman writers Statius and Martial both refer to the practice of collecting broken glass for recycling, and there is evidence to suggest that this took place in York. There may even have been an organised system collecting from surrounding settlements then bringing the glass into the city, just as there is today. Sadly, no-one has yet found a Roman Bottle-Bank!