GLASS FACTS by Glass & Art

GLASS FACTS by Glass & Art

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Medieval light

The Middle Ages in Europe are often considered to be a time of decline, though many historians constantly inform us about the great inventions and technological capabilities of the medieval European people. This dual line of thought also applies to the story of glass. Though the technique of glassblowing was generally continued in Europe, some technologies were gradually lost, such as core-forming, the making of cage-cups and the ability to blow larger glass sheets for windows. Especially in the early medieval times (6th to 9th century AD), glassblowing mainly consisted of blowing drinking vessels.

But decline is not the whole story: in medieval times, important innovations took place, especially in the field of stained glass. The first of these stained windows were produced in the 6th century in Italy (Ravenna). They found out that iron or copper oxide could be used to paint the glass. By heating the glass just to the point that it starts to soften, the metal oxides get fused to the glass. In this way, an eternal picture of light is created, perfect for decorating churches.


Since blowing larger glass sheets was no longer an option, people needed a solution to close the "wind-eyes" or windows of the churches and other big buildings. By placing pieces of coloured glass in lead profiles, they were able to make larger windows.  After the 10th century, larger and larger churches and cathedrals were build, demanding (especially in Northern Europe) larger and larger coloured stained glass windows. The result is the stunning walls of light that depict many Saints and Biblical stories to enlighten the often illiterate medieval Christian visitors. Below, you find a four-part series of the BBC about medieval stained glass.

Another very important development in the Middle Ages, was the rise of Venice, or more precisely Murano, as a world-leading centre for glass art. At first thought, it seems to be odd to establish so many furnaces in a Lagoon, while there little wood to fuel the fires. Further, due to lack of space the quite flammable houses on the islands were built extremely close together.  Not the most ideal spot to establish a flourishing glass industry. Initially many measurements were taken, which restricted the workshops in number, size, burning-hours and location. But Venice was the hub between Europe and the Byzantine Empire: they became rich by trading between cultures. The Venetians had seen the beautiful enamelled and golden glass art of the Middle East, which was far more elegant and sophisticated than the rather basic glassware that was produced above the Alps. Instead of importing the rather exotic, and of course quite breakable, glassware from Byzantium and ship it to Europe (as the Vikings did during the 6th to 10th century AD),  they imported the less fragile raw materials (glass ingots and enamels) and started to create glassware for the rest of Europe themselves. After the decline of the Byzantine glass industry in the 14th century, this development got an extra impulse.

The oldest furnaces found in the Venetian lagoons date back to the 7th and 8th century AD, but up to the early 14th century, glassblowing was just one of the many crafts practised in the lagoon, and the guild, the doge and other members of the aristocracy treated glassblowers just like any other artisans. Laws and policies were mainly directed at reducing the nuisance, minimizing the risks and promoting decency in trade. During the 14th century, Venetian glassblowing expanded rapidly, and the status of the glassblowers was to change drastically in the early 15th century, when Angelo Barovier entered the glassblowing scene of Murano: with him, the renaissance was also introduced in the world of glass.   

Late medieval glass horse. Glass Museum Murano.

Photo: Katinka Waelbers