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All About Glass

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About Medieval Glass

All About Glass

Glass in Ancient Rome

In the fourth and fifth centuries AD, the glassmakers of the Roman world were in a class of their own. Glassmaking and glassworking were separate activities. Glassmakers used tank furnaces to melt several tons of raw materials in one operation, and glass workers employed many techniques to make objects ranging from simple household utensils to sophisticated luxury objects.

Cage cups are among the Romans’ most remarkable creations in glass. An undecorated “blank” with a very thick wall was entrusted to a cold worker, who used cutting wheels and hand tools to remove two-thirds of the glass, leaving an openwork “cage” that enclosed the container. The %%metal%% attachments show that this cage cup was a lamp intended for suspension. The bowl contained oil and a wick, perhaps floating on a piece of cork. Imagine the patterns of light and shade %%cast%% by the flame when it shone through the cage.

The Migration Period

Cone beaker

The fifth and sixth centuries are often called the “Migration Period,” because peoples from outside the Roman Empire migrated into the former Roman provinces and established small, independent kingdoms. Among most of these groups, it was customary to bury the dead accompanied by personal possessions. These objects (including glass) provided 18th- and 19th-century antiquarians with raw material for the study of early medieval culture.

The study of early medieval glass is essentially the study of drinking vessels. Although most of the best examples of complete vessels have been recovered from graves, the occurrence of fragments of identical types of glass in settlements shows that the objects buried with the dead were the same as those used by the living. Some of the earliest glasses resemble those produced in late Roman times. The forerunners of claw beakers, for example, were made in Roman workshops in the third and fourth centuries.

The Vikings and Their Glass

The years between 800 and 1000 are the “Age of the Vikings,” referencing the collective name for many of the inhabitants of medieval Scandinavia. Eyewitnesses recorded with horror the bloodthirsty raids of Vikings in search of booty. But this was not the whole story. Sailing their long ships, the Vikings planted settlements in Iceland, Greenland, and even in Newfoundland in Canada. Meanwhile, Viking merchants traveled along the Volga River to the Black Sea, and Viking mercenaries formed the Byzantine emperor’s Varangian Guard.

At home in Scandinavia, and in northwestern Germany, the Viking merchants created trading centers, where archeologists have recovered artifacts from many parts of Europe and the Middle East, including glass vessels from western Europe. Indeed, some of the best preserved glasses of this period have been discovered in Viking graves.

The Later Middle Ages

Prunted beaker

Finds from archeological excavations show that most of the late medieval vessels used at home were intended for serving and consuming beverages. Paintings of the Last Supper, the Wedding at Cana, and Herod’s Feast depict tables set with one or more bottles of wine and a larger number of beakers or goblets — although not enough for everyone. Glasses were shared, as were knives and other utensils.

The beakers came in a variety of shapes and sizes. The smaller vessels often had barrel-shaped bodies, while the larger examples had tall, tapering sides. The ornament sometimes consisted of horizontal rows of “prunts” (small blobs of glass attached to the side of the beaker).

In southern Germany, Switzerland, and parts of Italy, the best late medieval glass was either colorless or almost colorless, and was the forerunner of Venetian cristallo of the Renaissance. This colorless glass was made by carefully selecting the raw materials and by adding a small amount of manganese oxide, a mineral traditionally known as “glassmakers’ soap” because of the way it removed the colors caused by impurities.

Forest Glass

Most vessels produced in the later Middle Ages in northern Germany, the Low Countries, and central Europe were made of transparent green forest glass, so-called because it was produced in small glasshouses located in forests, which provided a convenient source of fuel. Its color was caused by the presence of impurities, mainly iron oxide, in the raw materials.

A late variety of the prunted beaker was a vessel known as a Krautstrunk (German for “cabbage stalk”), so named because the ornament consists of large blobs projecting from the side of the vessel like the scars on a cabbage stalk after the leaves have been removed.

Feeding the %%furnaces%% to make glass consumed trees on a %%scale%% that alarmed the authorities. Because of this, in the forests of the Spessart Mountains of Germany, regulations limited the quantities of window glass and glass vessels that could be produced.

Glass and Holy Relics

Jug with coat of arms of Medici Pope

For centuries, Muslims ruled most of Spain and Portugal. There also were hundreds of Jewish communities, and people (especially on the edges of Europe) who continued to worship the old gods and goddesses. Late medieval Europe, however, was essentially Christian.

From the early days of the church, saints and their relics (parts of their bodies or objects associated with them) were revered by the faithful. Saints, with divine assistance, were believed to perform miracles. Items brought into contact with relics (such as oil from lamps burning above a saint’s shrine) were also venerated, and pilgrims took them home as evidence of their devotion. By the late Middle Ages, the cult of relics attracted pilgrims from all walks of life. One of the great works of medieval literature, The Canterbury Pilgrims by Geoffrey Chaucer, describes a group of pilgrims traveling from London to Canterbury to visit the shrine of St. Thomas à Becket.The exhibition includes two glass containers for relics borrowed from the Vatican.

Glass and Science

In the 12th and the 13th centuries, Latin translations of books written by ancient Greek and Muslim scientists began to circulate in Europe. Science and medicine were two fields that benefitted directly from new knowledge gained through improvements in glassmaking. Many scientific experiments depended on glass apparatus that were transparent and did not contaminate their contents by corroding.

No apparatus played a more important role in medieval experiments than the still, which was used for preparing acids used in alchemy (medieval science) and for distilling alcohol. In medicine, physicians used glass flasks for uroscopy: using the color of urine to diagnose disease.

Another result of the increasing use of glass for experiments was the development of lenses and the emergence of optics as a branch of science. The invention of reading glasses was a direct result of experiments with lenses. Spectacles, consisting of a pair of lenses assembled for wearing in front of the eyes, were invented in Italy. In 1279, a writer in Florence commented, “I am so debilitated by age that, without the glasses known as spectacles, I would no longer be able to read and write.”


In the 1400s, glassmaking in Renaissance Venice exploded like a grand display of fireworks. Venetians had been making glass for centuries, and even formed a guild (an association of people practicing the same trade or craft) by 1224. Thereafter, the Venetian glass industry is well documented. Consequently, we know that the flowering of Venetian glass in the 15th century had deep local roots.

The best Venetian glass made in the Renaissance has one or more of the following characteristics: colorless glass of great clarity, glass of brilliant colors that often imitated semiprecious stones, gilding and enameling, the extensive use of molds and twisted glass rods (known as canes) of two or more colors, and the assembly of elaborate objects from multiple parts. These elements were combined with new forms that appealed to a taste for exuberance, opulence, and technical perfection.

Published on September 27, 2011