At the suggestion of the International Commission of Glass (ICG), the UN has declared this year the International Year of Glass. Today’s essential material is an environmentally friendly and recyclable product that guarantees sustainable development.
On 18 May 2021, the 75th UN General Assembly approved the application by the International Commission of Glass (ICG) that 2022 be declared an International Year of Glass. Glass has accompanied humanity on its journey of development for nearly 3500 years. Today, as one of the most versatile and important inventions of mankind, it has become a dominant material in our everyday lives and has also taken a prominent position worldwide. Contrary to what many people assume, glass is not just a material for windows, glasses, or bottles. There is so much that can be made from glass, many special everyday objects that the layman might not even think of. Glass itself—a special shimmering wonder that can be worked hot or cold—is also an excellent imitation of precious stones.
The glass’s potential for innovation is limitless, making it an essential resource for the development of technology and science. It has the huge advantage of being a recyclable and environmentally friendly product thereby contributing to the achievement of the 2030 Sustainable Development Goals.
History of glassmaking
Glassmaking has a very long tradition, with many legends about its origins. According to one of these legends, glass was first discovered solely by the Jews, when they found a glass-like material formed by fusing ash and sand after a major forest fire.
The other legend comes from Pliny the Elder, who says that glass was discovered by the Phoenicians when sailors carrying soda were fleeing to shore from a storm. The sailors built a fire on the beach and propped up their vessels with pieces of soda. They observed the soda melting into a glass with the beach sand. However, these legends are not supported by archaeological evidence.
The first glass-like materials appeared in Western Asia and Mesopotamia sometime around the 5th–4th millennia BC. They appeared partly as by-products of ceramics manufacture, as glazes to make porous ceramics waterproof. Similar glazes were later used to coat fired clay beads. The first glasses may probably have had something to do with the metalworking that was developing at this time. Melting ores required more heat than firing earthenware and its glazes. It is very likely that the glass fragments that were produced at random in the process began to be used consciously and then produced. The first mixtures were based on sand, lime, and soda; colored with copper (molten malachite). Due to the rudimentary melting process and impurities in the raw materials, the glass was rendered opaque by massive air bubbles and inclusions. The Mesopotamian primary glass was made from two components: quartz sand and ash from salt-tolerant plants. A third ingredient is mentioned in a cuneiform text, but it has yet to be identified. In Egypt, glass production began in the New Kingdom by Asian glass workers brought from the Syrian campaign of Pharaoh Thutmose I. The Asians began by molding around a sand core, one of the most common techniques of the time. They formed the shape of the pot from the sandy clay and then coated the shape with the molten clay. The glass fibers that bulged out from the surface were popular decorations for the surface of the pottery. The fibers were mostly colorless, less often in yellow-opal shades. The thread decoration often imitated the coiling movement of a snake. The thin glass threads were combed with a wooden knife to form the characteristic motifs of Egyptian glass. After the glass had cooled, the clay core was pounded out. This process was only able to produce small perfume and balsam jars with various figures on them. Fish-shaped objects were very common.
The earliest authentic Egyptian glassware date from around 1470 BC, the so-called Thutmose III vessels. In Europe and the Middle East, glass was used in buildings as early as 500 BC. They were mainly used to fill small gaps in walls and as a rudimentary form of window glass. This function was preserved for a long time; fragments of it were found in Pompeii, destroyed in 79 AD. The blowpipe was probably invented by an unknown Sidonian master in the 1st century BC. Until then, larger glass objects could only be made by gluing. The shape and size of the blowpipe have changed little since then. The walls of the blown glass objects have become thinner and more even. The pipe was used to blow glass into clay molds, which appeared almost simultaneously with the invention of the pipe. The mould allowed the surface of the object to be decorated in relief: the indentations in the mold became the reliefs of the finished object. A typical type of mold-blown glass is the so-called Sidonian relief-decorated glass.
In the Roman Empire, the production of glass began to develop under Augustus. During the reign of Augustus, glass was also produced in Hispania and Gaul. The technology spread to the Rhine region from Gaul through Trier. At the end of the 2nd century AD, the glass industry of Colonia was already famous, and the processes developed there were adopted as a guideline for the whole Roman glass industry. The Romans always made glass from the same three raw materials: quartz sand, natural soda and limestone—this was the so-called Roman primary glass. The necessary soda (soda ash) was obtained from the saline areas of the Nile Delta, mainly from the Natron Valley (Wadi El-Natrun)—the valley from which sodium was later named.
The Romans made larger vessels, mainly for storing liquids. Glass remained opaque and colored; decolorization with manganese was only discovered in the 2nd century AD. Circus cups, also made in relief, appeared in the 1st century. These molded glasses were decorated with reliefs of various circus fights, most often chariot races and less often gladiatorial contests. They were made of transparent, colored or colorless glass, and were cylindrical or hemispherical. Victory beakers were also made using a similar technique. These simple cylindrical vessels were decorated with a wreath of amber leaves and an inscription in Greek commemorating the victory.
The fall of the Western Roman Empire was also the downfall of European glass art. Few glass objects were made in Europe between the 5th and 13th centuries. Glass was a luxury for the less wealthy, while the wealthier elite bought oriental products. The art and secrets of glassmaking were introduced to the Middle Ages by Byzantium, the Rhineland, and Venice.
New era of glass production, Venetian glass
The “Venetian glass” opened a new era in the production of both decorative and plate glass. Magnificent mirrors were made from colorless, clear glass with a brilliant glow. Glass mirrors on a metal plate have existed since ancient times but the first glass mirrors coated with lead-mercury amalgam were made only in 1240. A lead plate was placed on a marble slab and mercury was poured over it. A plain glass plate was clamped onto the resulting amalgam, and the surface of the glass was coated with a hair-thin layer of amalgam reflecting silver light. Over time, lead was replaced by the more expensive but non-toxic silver. By the end of the Middle Ages, the price of Murano mirrors had risen to rival that of gold. In Venice, most houses were made of wood, and frequent fires forced the glassmakers to leave the republic. In 1291, the island of Murano, one and a half kilometers from Venice, became the center of glassmaking.
The center of glassmaking, Murano
Glassmaking was a respected profession. Masters received nobility, their names were inscribed in the golden book of Murano, and their daughters were eligible to marry into the noblest families. To prevent knowledge from falling into the hands of foreigners, they were not allowed to leave the territory of the Republic. Anyone who did share the secret with neighboring cities or countries was liable to severe punishment. For centuries, Murano’s excellent glassmakers enjoyed a monopoly on the production of quality glass.
Their best-kept secret was the way they made filigree glass. The essence of filigree glass is that there were threads of milk glass in the wall of transparent glassware. Strips of fused milk glass were placed on the walls of a metal mould, then the transparent glass was blown into the mold, to which the milk glass strips had adhered. The clump of glass was dipped again in a transparent glass mass and blown into a vase, jug or other objects. The delicate decoration was visible in the finished glass ornaments.
No wonder Murano glass is now a household word. European rulers saw how much did Venice benefit from glass, and began to develop their own glass industry. They encouraged Venetian glassmakers to settle in their country, in case they failed, invited glassmakers from other Italian cities. Venetian-style glassware was managed to copy by the 15th and 16th centuries, first in a few glassworks in the German–Czech-speaking area, including Hall and Innsbruck in Tyrol and Munich and Nuremberg in Bavaria. It was from these centers that the new-fashioned glass spread to other parts of Western Europe, including France and England. Documents referring to “Venetian-style glassworks” do not always distinguish between glassmakers who immigrated from Venice and those from other Italian cities.
For a long time, glassware was primarily decorative objects. Accordingly, glassmaking was for a long time a single profession: glass was shaped and decorated where it was made. In the Habsburg Empire, the production of Czech crystal glass (in Bohemia) and glass cutting (in German-speaking areas) became distinctly separate, and then diverged with the mass production of glass on an industrial scale, since most glassware became everyday objects. The history of glass as a whole can therefore be traced back to the turn of the 19th and 20th centuries.
Jewelry made of cut glass: Swarovski crystals
Swarovski crystals also occupy a prominent place in the art of glass shaping. The history of jewelry made from cut crystal glass goes back to Daniel Swarovski, born in 1882 in Bohemia. At that time, Bohemia was a hotbed of crystal and glass production. Swarovski was an apprentice in his father’s glass foundry. At the age of 19, he had already created an electric crystal cutter, which he later patented. After finding financiers, Swarovski set up a new company in Wattens in the Austrian Alps, Tyrol, where they managed to build up their power. From here, Paris and the important customers were relatively more easily accessible. By the late 19th and early 20th centuries, crystals were already adorning formal evening dresses. It is no coincidence that they quickly caught the attention of the fashion industry. In 1908, Daniel’s three sons joined the family business. During these years, they developed a tool similar to a grinding stone, which was introduced in 1919. The Swarovski company managed to survive World Wars I and II, allowing the firm to expand further through its subsidiaries.
In 1956, Daniel Swarovski died at the age of 94, but his descendants still actively manage D. Swarovski & Co., one of the world’s leading manufacturers of quality crystal glass jewelry. They are present in more than 120 countries worldwide. The emblem of the company is also a symbol of purity and elegance, a swan silhouette. The company colors are midnight blue and “Swarovski red”. Two collections a year are released: autumn-winter and spring-summer, which include more classic, fashionable and extravagant jewelry, bags and watches.
The evolution of glass technology in the 19th century
In 1806, Joseph von Utzschneider (1763–1840) produced optical glass. Its production was further developed by Joseph von Fraunhofer from 1813 onwards.
In 1830, glass pressing was invented.
In 1843, Thomas Drayton coated the back of mirror glass with silver nitrate, thus pioneering modern glass mirror production.
Cast glass was first (in 1846) rolled into slabs by Henry Bessemer.
The first furnace with a brown-coal powered generator was installed in Zwickau in 1850 by Friedrich Christian Fikentscher (1799–1864).
In 1856 the Siemens brothers Carl Wilhelm and August Friedrich invented regenerative combustion.
Sandblasting was invented by Benjamin Chew Tilghman (1821–1901) in 1871.
Tempered glass was invented by Francois Barthelemy Alfred Royer de la Bastie (1830–1901) in 1874. The heat-proof glass was produced by Friedrich Otto Schott (1851–1935) in 1885.