Venetian Glass

Venetian glass is a type of glass made primarily in Venice, Italy. It is world-renowned for being colorful and elaborated, developed by the thirteenth century. Towards the end of the century, the centre of the Venetian glass industry moved to the small Murano island.

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Murano Venetian glass vessels. Three classic forms including a dolphin ewer of traditional techniques

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When was glass discovered?

People had used naturally occurring glass, especially obsidian (the volcanic glass) before they learned how to make glass. Obsidian was used for production of knives, arrowheads, jewelry and money.


first example of glass artifacts

The ancient Roman historian Pliny suggested that Phoenician merchants had made the first glass in the region of Syria around 5000BC. But according to the archaeological evidence, the first man made glass was in Eastern Mesopotamia and Egypt around 3500BC and the first glass vessels were made about 1500BC in Egypt and Mesopotamia. For the next 300 years, the glass industry was increased rapidly and then declined. In Mesopotamia it was revived in the 700BC and in Egypt in the 500’s BC. For the next 500 years, Egypt, Syria and the other countries along the eastern coast of the Mediterranean Sea were centers for glass manufacturing.

In the beginning it was very hard and slow to manufacture glass. Glass melting furnaces were small and the heat they produced was hardly enough to melt glass. But in the 1st century BC, Syrian craftsmen invented the blow pipe. This revolutionary discovery made glass production easier, faster and cheaper. Glass production flourished in the Roman Empire and spread from Italy to all countries under its rule. In 1000 AD the Egyptian city of Alexandria was the most important center of glass manufacture. Throughout Europe the miraculous art of making stained glass on churches and cathedrals across the continent reached its height in the finest Chatres and Conterbury cathedral windows produced in the 13th and 14th centuries.

info source: http://www.historyofglass.com/

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When the first Venetian glassworks were developed?

The origins of glassmaking in Venice go back to the times of the Roman Empire when molded glass was used for illumination in bathhouses. Blending Roman experience with the skills learned from the Byzantine Empire and trade with the Orient, Venice emerged as a prominent glass-manufacturing center as early as the 8th century. One of the earliest furnaces for glass on a Venetian island, dating from the 8th century, was discovered by archaeologists in 1960.

By the late 1200s, the production of glass objects of the finest quality was the city’s major industry as confirmed by the establishment of the Glassmakers Guild that laid out rules and regulations for the craftsmen. The purpose of the guild was to safeguard the secrets of the trade and ensure the profitability of the industry. In line with these objectives, a 1271 law prohibited the importation of foreign glass or the employment of foreign glassworkers.

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1300’s Murano Glass

An even more radical law was passed in 1291 that laid the ground for the establishment of Murano as a premier glass-manufacturing center. This law required that all furnaces used for glassmaking be moved from Venice to Murano to avoid the risk of fire from the furnaces spreading onto the largely wooden structures of overpopulated Venice. Many historians agree that the true motive for this law was to isolate the glass craftsmen to a location where they wouldn’t be able to disclose trade secrets. A subsequent law passed in 1295 forbidding the glassmakers from leaving the city confirms this theory.

Artisans working in the glass trade were well rewarded for their efforts. They had a privileged social status, and their daughters were allowed to marry into the wealthiest and noblest of Venetian families. By applying this clever approach, Venetian government ensured that the glassmakers encouraged their offspring to carry on the trade, and that trade secrets stayed in the families and fueled creative processes leading to innovation and further success. This, along with Venice’s convenient location at the crossroads of trade between East and West, gave Venice monopoly power in manufacturing and selling quality glass throughout Europe that lasted for centuries.

info source: https://www.glassofvenice.com/murano_glass_history.php

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How was murano glass produced?

Today, we might naturally be inclined to think that glass is not particularly difficult to make. However, we will see that, in Renaissance Venice, glassmaking was a complicated, laborious, and expensive enterprise.
It would be difficult to find a more unlikely place for locating a glass industry than on the islands of Venice and Murano, which are small and surrounded by shallow waters. None of the essential elements involved in the making of glass were either native or located nearby.

FIG. 45. Armorial goblet, blown, mold-blown, tooled, enameled, gilded. Venice, possibly 1480–1490. H. 19.7 cm, D. (rim) 13.3 cm, (foot) 13.4 cm. The Corning Museum of Glass (79.3.193, bequest of Jerome Strauss).
Armorial goblet, blown, mold-blown, tooled, enameled, gilded. Venice, possibly 1480–1490

Raw materials were imported from near and far. In Renaissance Venice, glass required what would be called, in modern glassmaking terminology, a former, a flux, a stabilizer, and a decolorizer.
The former was silica. Glass can be made using beach or river sand, but sand is often accompanied by iron, an element that turns glass green. We know that, by the middle of the 14th century, the Venetians were importing quartz pebbles from the Ticino and Adige Rivers as their source of silica. The pebbles, reasonably free of iron, were pulverized into fine powder before they were used.
The flux, which was essential for lowering the melting point of the silica, was acquired in the form of plant ash. As early as 1285, this was being imported from Syria and Egypt. Later, coastal plants from Sicily and Spain were imported, carefully processed into soda di Catania, and used as a flux.
Less clear are the possible sources of the stabilizing agentsalumina, lime, and magnesia. Modern chemical analysis of diverse samples of Renaissance Venetian glasses reveals their presence, and we can be sure that the glass contained effective stabilizers because so many objects survive intact. Among scholars who specialize in this subject, it is apparently still uncertain whether stabilizers found their way into the glass in the form of “pollutants” or whether they were added intentionally in some as yet unidentified form.
The last key ingredient in the making of reasonably colorless glass was manganese dioxide, sometimes colloquially known as “glassmakers’ soap.” The use of this compound as a decolorizer in glassmaking has been known since at least 1290. It was acquired in the Piemonte region of Italy, some 250 miles west of Venice.

FIG. 47. Winged goblet, blown, applied, tooled. Probably Venice, 17th century. H. 17.3 cm, W. 11.1 cm, D. (foot) 11 cm. The Corning Museum of Glass (2000.3.13).
Winged goblet, blown, applied, tooled. Probably Venice, 17th century.

 

 

info and image source: http://renvenetian.cmog.org/chapter/material-making-glass-renaissance-venice

What are murano glass main decorative techniques?

DIP (OPTIC) MOLDING

Glass decorated by using a cylindrical or truncated conical one-piece mold with a patterned interior. The mold is open at the top so that glass can be dipped in to create a pattern on the exterior of a gather of glass or on a bubble.

 

 

WRAPS

Threads of glass that extend around a vessel.

 

 

 

 

FILIGRANA

(Italian, “filigree glass”) The generic name for blown glass made with colorless, white, and sometimes colored canes. The filigrana style originated on the island of Murano in the 16th century and spread rapidly to other parts of Europe where façon de Venise glass was produced. Manufacture on Murano continued until the 18th century, and it was revived in the 19th century.

FAUX RETICELLO

A technique which produces an appearance similar to traditional reticello without the bubble at the intersection of the canes.

 

 

FULL-SIZE MOLD-BLOWING

Inflating a parison of hot glass in a mold. The glass is forced against the inner surfaces of the mold and assumes its shape, together with any decoration that it bears.

 

 

GILDING, HOT APPLIED

The process of decorating glass by the use of gold leaf, gold paint, or gold dust. The gilding can be applied with size, or amalgamated with mercury. It is then usually attached to the glass by heat. Gold leaf can be picked up on a gather of hot glass.

 

COLORED FRIT, TWISTED AND MANIPULATED

Batch ingredients such as sand and alkali, which have been partly reacted by heating but not completely melted. After cooling, frit is ground to a powder and melted. Fritting (or sintering) is the process of making frit.

 

A PENNE (COMBED THREADING)

Decoration in which a spiral thread (wrap) of colored glass (usually white) is manipulated with a tool to create a festooned pattern on the surface of a vessel.

 

 

SPECIAL EDGE SHAPES

Shaping edges by slumping or molding a hot vessel

 

 

 

 

CHALCEDONY/AVENTURINE GLASSES

Glass marbled with brown, blue, green, and yellow swirls in imitation of chalcedony and other banded semiprecious stones. Calcedonio was first made in Venice in the late 15th century.

(from French aventure, “chance”) Translucent glass with sparkling inclusions of gold, copper, or chromic oxide, first made in Venice in the 15th century. Aventurine glass imitates the mineral of the same name, a variety of translucent quartz spangled with mica or other minerals.

KUTTROLF STEM

(German) A flask with the neck divided into two or more tubes. The Kuttrolf, which has Roman antecedents, was produced by German glassworkers in the later Middle Ages; it is also found among Venetian and façon de Venise glasses of the 16th and 17th centuries.

INTERNAL DECORATIVE ELEMENT

A bulb of colored glass (usually aqua) attached within the interior of a vessel.

 

 

 

FREE-FLOATING RINGS

A decoration in which rings of glass are trapped (but not fixed) on the exterior of a vessel, using tiny strips of molten glass.

 

 

 

ICE GLASS

A decorative effect that causes the surface of the glass to resemble cracked ice. This is achieved by repeatedly plunging a parison of hot glass into cold water and withdrawing it quickly. The thermal shock creates fissures in the surface, and these impart a frosted appearance after the parison has been reheated to allow the forming process to continue.

MILLEFIORI

A decoration achieved by embedding in molten glass small slices of canes that have regular patterns of contrasting color.

 

 

 

FLAMEWORKED

The technique of forming objects from rods and tubes of glass that, when heated in a flame, become soft and can be manipulated into the desired shape. Formerly, the source of the flame was an oil or paraffin lamp used in conjunction with foot-powered bellows; today, gas-fueled torches are used.

 

MORISE (BIT-WORK)Tiny amounts of molten glass that are added atop other decorative elements (such as “wings’), then manipulated with tools.

 

 

 

PRUNTS

A blob of glass applied to a glass object primarily as decoration, but also to afford a firm grip in the absence of a handle.

 

 

 

ENAMELING AND GILDING (BOTH APPLIED COLD, AND THEN FIRED)

Enamels consist of intensely colored glass (or colorless glass that has been mixed with a metallic oxide) that has been finely ground and mixed with a liquid medium to facilitate painting. After its application to a cooled object, the decoration is fired at a high temperature for permanence. Gold is usually applied in the form of leaf or slightly thicker foil; the gold and enamels are fired together.

info and image source: http://renvenetian.cmog.org/visual-guide

What is the difference between Murano glass and any other glass?

Murano glass is glass in a chemical sense of the word. However, Murano glass is as different from, say, the glass in your window panes, as Rembrandt paintings are different from an empty canvas. Murano glass is created only on the island of Murano, located within the borders of the city of Venice in Northern Italy. This glass is made from silica, soda, lime and potassium melted together in a special furnace at a temperature of 1500°C to reach a liquid state. Gold or silver foil are often added to the glass mixture, along with such minerals as copper for sparkles, zinc for white color, cobalt for blue, manganese for violet, and so on.

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Magnificent example of murano glass artifact

The mixture is then mouth-blown or hand-crafted by master glassmakers using special techniques and basic tools, many of which have been developed in the Middle Ages and changed little since then. This method of glass-making results in unique creations with rich coloring and beautiful, sometimes surreal, patterns and shapes, deserving to be called “works of art”. Even though beautiful glassware has also been created in other places around the world, none of the glassware still being produced has such rich history and so much artistic value as Murano glass.

info source: https://www.glassofvenice.com/blog/2010/02/what-is-the-difference-between-murano-glass-and-any-other-glass/

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