History of Glassmaking

Glass has been used for a very long time, even in the Stone Age. At the time, people found glass by accident. Glass is formed naturally when rocks melt in high temperature; two main ways in which natural glass occur are when lightning strikes sand, or when volcanic eruptions happen and then the area cools down and solidifies rapidly. So unless such natural events had happened, people could not find glass.

Natural glass is green or bluish green in color because of iron impurities in the sand. So during stone age, people could not find glass as we know it today. (Transparent, pure, etc.)

Colored glass can be made by adding metals and mineral oxides, but such skills have developed only later in the history of civilization. While it is not known exactly when people first began to make glass themselves, ornamental glass in forms of beads, seals, and decorations have been found from around 2500BC and glass making was first recorded in ancient Rome, Egypt, and Syria. In the beginning, glass was used to produce glazes on pots and vases. After 1500 BC, Egyptians began to produce glass pots and vases. Glass was rare and hard to make in early civilization; thus, it was considered to be as valuable as jewels, and only the ruling classes could afford them.

(* I found the picture by googling under "labeled for reuse," and put a link to the source.)

Lucky for us, many Egyptian glass works are preserved well, because of their culture of burying the worldly goods of the dead and the dry climate that prevents decay.

Egyptians were very ahead of the game regarding glass making; they knew before 3000 BC how to use glaze techniques. In the early periods, they created glass pieces modeled after stone or ceramic objects. They also created glass beads, which were highly prized, almost as much as gold and precious stones. Egyptians were also active in the trade of glass objects so that they could spread their techniques and style.

Glass vessels in the round, hollow form that we know appear only after 1500 BC, and it is thought that the conquest of Near Eastern lands triggered the sudden appearance of glass vessels in Egypt.

One common method of glassmaking used by Egyptians was "Cire perdue." The piece was modeled in wax, and then covered with clay. Then the wax would be melted and poured away, so that the gap could be re-filled with molten glass.

Another, most common method was molting glass on a core. A core (made of clay, mud, or straw) in the shape of the desired piece was formed on a metal rod. Then, the core was dipped into molten glass. When the walls of the core with added glass became thick, the object was marvered and annealed. Lastly, the core was removed, leaving a rough interior.

Sky blue and dark blue were some popular colors for glass in Egypt, together with gray, yellow, white, and orange. In later periods, red, green, and violet also appeared and added more variety for the tastes of the wealthy.

Unfortunately, Egyptian glassmaking depended greatly on political circumstances as it frequently does in any other country; thus, between 1200BC and 900BC when the country was in decline, there is little development in glass production.

Later under Alexander the Great and the city of Alexandria, where many Egyptian craftsmen worked, the glass industry flourished again. Alexandria became a center of glassmaking, and Greek culture is also reflected in its style.

In 27 BC Egypt was eventually conquered by the Romans, but its glassmaking style remained for a time after that. Through Roman conquests and trade.

(The picture used was marked as 'labeled for reuse' under google image search)

Between 27 BC and AD 14, Syrian craftsmen began the art of glassblowing. Long thin metal tubes were used for the blowing process and this technique has remained almost unchanged for thousands of years since then. The function of these blowpipes was to make glass production much easier, faster, and cheaper. With this tool, air is puffed into a molten portion of glass at the end of the blowpipe to make the glass into a desired shape. It is still a widely used method for glass-forming these days.

Easier production of glass led to widespread use by the common people. During this period, glassmakers also learned how to make transparent glass and how to decorate glass, so indeed this was a time of growth and prosperity for glassmaking.

(* I found the picture by googling under "labeld for reuse," and put a link to the source.)

The term "Roman glass" is a very broad, general term, and refers to a specific age under Roman rule as opposed to a specific area. The Roman Empire was so vast that there were many different styles coexisting within its realm, even though a unifying "Roman" theme can be recognized throughout the pieces.

In the 1st century BC, glassblowing was invented in Syria. In the same period, the Roman Empire was founded, and through its conquests and trade it subsequently spread a unique culture.

Alexandria and Syria exported their glassware to Rome, from which the works were then brought to Roman colonies in Europe. Thus, Rome was critical in spreading the art of glassmaking to Europe.

In 1st century AD, large scale glass manufacturing occurred in Syria, Palestine, and Alexandria. One Syrian glassmaker called Ennion even left his name on his glassware. Generally, Syrian glassmakers often produced utilitarian glassware, while Alexandrian glassmakers focused on luxury objects. Many also moved to Italy and other Roman colonies, and glass houses spread quickly through Europe. Soon, Cologne became a glassmaking center as important as Alexandria. The styles of these different locations were very similar to each other.

Like this, the Roman period started an unprecedented flourishing in the glass industry, during which even the common people began to have access to glassware. Some household glass types that were commonly used were janus flasks, which displayed the head of persons on a flask, and victory cups, with laurels and inscriptions for decoration. Mirrors and windows were also produced using glass.

Artistic glass also continued to be produced. For example, cage cups, which were bowls or cups with rounded sides, were created. These cups had pierced decorations attached by struts. This decoration was not fused to the surface; instead, the entire object was created out of a solid block of glass by under-cutting. Because the process is so complex, surviving pieces are very rare and it is difficult to reproduce even today.

After the fall of the Roman Empire in the 5th century, the glass industry also suffered a dramatic decline. With arts and crafts, there is a general tendency to follow the up and downs of politics. This tendency is even more marked in more expensive types of art that is considered a 'luxury'. Thus, while utilitarian glassware was still produced, artistic glassware naturally lacked demand as political and economic circumstances were unstable and people could not afford to buy luxury.

(* I found the picture by googling under "labeled for reuse," and put a link to the source.)

With the decline of the Roman Empire, many craftsmen abandoned their trade or stopped developing their skills. However, glassmaking did not cease and continued to develop in Venice, which boasted elaborate guild systems. Glass sheets were produced for the first time in the Middle Ages, and stained glass windows appeared in public buildings and homes.

The Crusades also played a crucial role; the conquest of Constantinople in 1204 opened up trade routes through the Eastern Islamic territories, and extensive cultural exchange occurred.

Especially, the famous Venetian island of Murano was the center of another period of advancement in glassmaking in the 14th century. Murano was a group of islands to the North of Venice and became the first world leader in glass manufacturing. Venetian Murano glass was special because local pebbles were made of almost pure silica and were ground into fine sand and combined with soda ash to produce high quality glass. Venetians held a monopoly in producing this superior form of cristallo glass (nearly transparent glass that can be blown into almost any shape), and with it made bowls, vases, and other types of glassware.

Venetians were also renowned in trade and supplied their craftsmen with proper material and know-how from other parts of the world; Venice interacted with Islamic states to share glassmaking methods and styles, and even had a protectionist rule against imported foreign glass.

There is a famous story related to this protectionism. It is said that the city centered glassmaking on the island of Murano instead of mainland Venice because it feared that fire from the foundries might burn down the city's wood buildings. However, some sources state that one of the main reasons for moving the industry to the island was that the city could ensure that no glassmaking skills or secrets were exported. Thus, while glassmakers were respected as prominent citizens of Venice, they were restricted in their freedom to move out of the Republic. They were virtual prisoners, and there were rumors whether the excuse of moving all the foundries because of fear of fire to the island were true.

Nevertheless, in this way, glassblowing remained a lucrative monopoly trade for Venice. Many glass pieces in this period were still luxury items, although some useful application of glass was seen in mirrors.

A lot of different countries imitated Venetian style. For example, in 1674, George Ravenscroft introduced a new type of glass, called lead glass or lead crystal. Lead glass was at first a substitute for the Venetian glass produced in Murano, and had some drawbacks because it developed crizzling (deterioration through cracks) within 1-2 years. Ravenscroft worked to fix this drawback, and this finished version of lead glass used higher proportions of lead oxide instead of potash. This new type of glass was ideal for optical instruments and was suitable for deep cutting and engraving, while Venetian cristallo was too fragile for such decorations. Some pieces with the original Ravenscroft seal still exist today, while some of them have crizzled.

(* I found the picture by googling under "labeled for reuse" and put a link to the source.)

For thousands of years, glassmakers have created glass works that are both functional and decorative. So how is glassware produced in the first place? Here methods for creating handmade glassware will be covered.

1. Into the furnace

Silica, alkaline flux, and other ingredients are mixed together into a batch (dry powder). The top of the furnace is usually in the shape of a dome so that a constant temperature could be achieved by deflecting the heat downwards. Until around the Industrial Revolution, wood was a common source of fuel for the furnace, and later coal. Peat, oil, gas, and electricity are also used.

The furnace is kept at 1300-1500 degree Celsius, and the melting process can take up to 48 hours. Many times the furnace is never turned off. Impurities rise up to the surface, which can be skimmed off. When the glass is completely molten, it can be shaped with a blowpipe or other methods.

2. Glassblowing

A blowpipe or pontil, about 6 ft long, is heated. Glass is attached to the thickened end of it. The glassmaker would make glass smooth and symmetrical by twirling and moving the blowpipe, and then reheat it and blow into a bubble by breathing into the pipe. In this way, the glassmaker could make glass into a desired shape and thickness to make hollow glassware such as a drinking glass or other vessel.
The glasshouse is usually staffed by a large workforce, and in many cases cooperation on a single article is absolutely necessary. Nonetheless, in many studios the main artist (whose name is usually the brand) will put special attention into each piece in order to keep high standards.

3. Annealing

All glass must be annealed. In this process, the finished item is heated in a special furnace, a lehr, and then cooled gradually. This reduces the risk of fracture.

4. Industrial glass production

Free-blowing and mold-blowing has changed little since the Roman days. Even in the early factories, a lo t of glassware was handmade, even though division of labor may have existed. However, in the 19th century, mass-production of glass developed. For example, in the mold-pressing method, molten glass was poured into a metal mold and "pressed." Such production methods were a cheap alternative to expensive handmade glass.

5. At the lamp

For small glass objects, the craftsman can work at the lamp. This method has also existed since the Roman times. Rods of annealed glass are heated in the concentrated flame of an oil lamp or Bunsen burner and shaped by using tools.