From what I've gathered things seem rather muddled in the early medieval period in regards to glass, but then again I don't study much about that. There are glassware finds from the Migration and Viking eras, but I have no clue about the commoness of such items. by the turn of the 14th century glassware and luxury pottery items seem to be relatively popular such that I would be comfortable putting a couple of items in for a well-to-do impression. By the end of the 15th century, though, local production seems more common and vessels are more utilitarian in nature (this seems also a trend in pottery as well).Below are gleanings from some sources I have access to. If you have any specific questions I'll be happy to try and expand.
Mitake.
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Rachel Tyson - Medieval Glass vessels found in England c AD 1200-1500...
Potash glass production centers could be found in England (sussex/surrey), Germany (Weser, Spessart, Hessen, Sw Black Forest), France (Argonne, Normandy), and Bohemia (known to have a distictive style from tat of german glass).
Soda ash glass production was more centered around the mediterranean. Enameled glass from syria and egypt begining in the late 12th century. Middle Eastern glass centers listed include Aleppo (very transparent, high quality), Damascus, Raqqa, Tyre, Antioch, Fustat. Venice was certainly a major player in luxury glass production, by 1271 they were issuing regulations controlling imports. There also glassware forms associated with other production centers in Italy and southern france. Spain has known production centers from the 12th century onwards.
Production areas for high lead glassware is uncertain, but finds seem to be concentrated in a England, the Low Countries, and northern Germany
According to the English finds (1261 total finds) Goblets, Beakers, and bowls were most abundant in the late 13th- early 14th c; Jugs and Flasks most abundant late 14th- early 15th c; Distilling vessels most found from 15th c contexts; and Lamps and Urnials most commom from the 15th - 16th c finds. Flasks/Urinals were by far the most common, comprising 606 of the total finds, 200 in the late 15th c time slot and 105 in the 14th century time frame. The other noted shift is that the 13th-14th century finds seem more high quality imported wares, whereas the 15th -16th centuy finds are much more utilitarian in nature.
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The Golden Age of Venetian Glass - Hugh Tait
Documentary evidence for some amount of glass making in Venice by the end of the 10th century. The glassmakers were a well established guild by 1268 when they participated in the inauguration of the new Doge carrying water-bottles and scent-flasks.
There is no firm evidence that there was or was not a break in the glass making tradition of the Romans in venice. Remains of a furnace dating to AD 600-650 have been found on one of the islands in the lagoon.
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Glass: 5000 years; ed Hugh Tait
This is more of a coffee table book and is a bit harder to glean firm facts and ideas from. Chapter 3 deals with early medieval 450-1066, Chapter 4 is Islamic and Chinese glassware, and Chapter 5 covers Europe form the the 10th century to the industrial evolution.
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Less scholarly but accessible via the web, Northerner.com has a number of pictures are reproduction glassware with information on the time period and place of the find that each reproduction is based on. Many of the forms can be seen in Tait.