In the West, the glassmaking industry was disrupted abruptly and thoroughly in virtually all the places where the chaos of invasion and upheaval paid call: the Rhineland, Gaul, Britain, and eventually Spain, Italy, and North Africa as well. It happened first at the Rhine, already in the 4th century CE, and the disruption of glassmaking is directly connected to the disruption of many hundreds of other sister industries which had flourished during the High Empire. Empire-wide connections ("trade routes," business relationships, supply lines, customer contracts) were severed by local and regional upheaval and were not easily repaired. Glassmakers depended on raw materials, as all industries, and the globalized economy of the Roman Empire meant those materials were often coming from far away as the cogs of very complicated economic machinery whirled. The archaeology of Rhineland areas shows a contraction of Roman and Roman-influenced cities from the 3rd century onwards, on the whole, but even at places which still managed to flourish (like Cologne), many of the familiar industries of the High Empire disappear or are severely reduced. Glassmaking seems to move from the urban environment and into the forests, perhaps to be nearer to the forge fuel they required in very large quantities. What is being produced at these forest workshops by the late 4th and into the 5th centuries BCE looks much more "Germanic" than "Roman," and that happens very rapidly. A similar, though delayed, picture is seen in Britain, where in the wake of pressure from Picts and Saxons, the former "Roman" glass workshops very rapidly become not-Roman. The repertoire of shapes in glass dries up, variety disappears, and by the end of the 5th century CE, the dominant glass shape by far is the famous conical beaker (like this), a shape which had very little to do with Romans tastes. But: the technical skill of many of these vessels does point directly back into the heyday of glassmaking from some centuries previous. Unlike in other areas, the technical abilities of glassmakers does not seem to vanish overnight, though their customers are now clearly very different and their customer base has very clearly shrunk dramatically.

This is a very abbreviated account, and focuses on the west. In the Byzantine sphere, there is a completely different story. A great place to follow the trail of Roman to Byzantine glassmaking is Roman glass : reflections on cultural change put out by Fleming (U Penn Museum, 1999), nicely illustrated and with generally easy-to-follow discussion of Roman glassmaking in its social and historical context.