Glass production prospers in Alexandria c. 1st century AD. Early glass makers produce colored beads and later utensils. With clear glass, Alexandrian alchemists can see their processes bubbling or fusing within, as in the transparent stomach of Shennong.
Shennong is a Chinese folk hero, divine farmer, healer and organic scientist who eats up to 70 poisons a day and watches their reactions in his transparent stomach. He teaches humans about farming, herbs and toxicology.
Alchemical processes use glass vessels, many with shapes specific to their purpose, for example distillation. Alexandrian alchemists of the first centuries AD are fascinated and delighted with glass vessels. They can see processes at work and monitor conditions.
Natural glass forms in quickly cooled conditions such as volcanic lava pouring into the sea or extruding through the slope. The first plentiful natural glass is obsidian, found in volcanic zones. East of the Black Sea, a Neolithic obsidian processing center operates c. 9000 BCE.
Other types of natural glass include moldavite, thought to come from the impact of meteorites; and Libyan desert glass created by a bolt of lightning fusing sand with sudden intense heat.
The art of glassmaking goes back to at least 3800 BCE, long before humans master the technique of making bronze. Based on archaeological finds, the first genuine synthetic glass is crafted in regions like Lebanon, coastal north Syria, Mesopotamia, or ancient Egypt.
The earliest glass artifacts date back to the mid-third millennium BCE. They're primarily beads, potentially originating as accidental by-products of metalworking (slags) or during the production of faience, a glass-like material created through a process akin to glazing.
Early glass is often non-transparent, containing impurities and flaws, technically classified as faience rather than authentic glass, which emerges c. 15th century BCE. Red-orange glass beads uncovered from the Indus Valley Civilization date before1700 BCE.
Initially, glass production relies on methods borrowed from stone working. It involves grinding and carving glass while it's still cold, using processes similar to those of carving clear quartz or rock crystal. The jug below is carved of quartz.
According to Pliny the Elder, Phoenician traders are the first to stumble upon glass manufacturing techniques at the site of the Belus River. Georgius Agricola, in De re metallica, reported a traditional serendipitous "discovery" tale of familiar type:
"The tradition is that a merchant ship laden with nitrum [niter] being moored at this place, the merchants were preparing their meal on the beach, and not having stones to prop up their pots, they used lumps of nitrum from the ship, which fused and mixed with the sands of the shore, and there flowed streams of a new translucent liquid, and thus was the origin of glass."
History says glass arrives on the scene before Phoenicians, but it's a good story. Pliny also believes rock crystal is ice frozen so long it's become stone. However he's the first to discover amber is a resin. It's kind of hit and miss with Pliny.
Continuous glass production starts c. 1600 BCE in Mesopotamia and 1500 BCE in Egypt. In the Late Bronze Age, major advances in glassmaking occur. Discoveries from this era include colored glass ingots, vessels, and beads.
By the 15th century BCE, significant glass production happens in Western Asia, Crete, and Egypt. The Mycenaean Greek term ku-wa-no-wo-ko-i, translating to "workers of lapis lazuli and glass" is documented.
It's believed the knowledge and techniques needed for initial glass fusion from raw materials are as a closely guarded secret. Consequently, glassworkers in other regions have to rely on imported preformed glass.
The Bronze Age collapse of c. 1200 BCE halts glass production. It starts again in Syria and Cyprus, c. 9th century BCE, with the discovery of techniques for producing colorless glass.
The oldest known glassmaking "manual", cuneiform inscriptions, dates back to c. 650 BCE.
Diving bells, described by Aristotle in the 4th century BCE, mark significant advancement in underwater exploration and engineering. Aristotle's student Alexander the Great has a remarkable glass diving bell made.
Legend has it Alexander uses the diving bell during the Siege of Tyre in 332 BCE. The use of a diving bell in this context demonstrates the advanced techniques and versatility of glassmaking technology.
The term "glass" originates in the late Roman Empire, from a Roman glassmaking hub in Trier, Germany. The substance is known as "glesum," referring to a clear, shiny material.
Roman glass artifacts are found throughout the Roman Empire in homes, burial sites and areas of industry. Like faience, glass is a desirable item of trade. Roman glass appears in such diverse places as China, the Baltics, the Middle East, and India.
The earliest method involves molten glass around a clay or sand core. The mold is heated and the molten glass fuses around it, leaving a hollow. This creates a container for everyday use. To make different colors, Alexandrians melt glass, add color and remelt when the color sets.
Glass items from molds are all made a similar way. The mold can be graphite, silicone or metal. Molten glass is poured into the mold and left to harden. Once hardened, it's removed from the mold. Extra glass in the middle is scooped out and remelted later.
In the 1st century AD, the industry experienced swift technological advancement with the innovation of glass-blowing and the prevalence of clear or 'aqua' glasses. The production of raw glass and the crafting of finished vessels were carried out in different geographic areas.
By the conclusion of the 1st century AD, extensive production, mainly in Alexandria, lead to the widespread availability of glass as a common material in the Roman Empire. 1st century alchemist Mary the Jewess enthuses over the glass vessels and invents a few too.
Glassblowing is invented by Syrian craftsmen around Sidon and Aleppo in the 1st century BCE. Blown vessels are created for everyday and luxury use. Produced commercially, they're exported to all parts of the Roman Empire.
It looks easy but takes time to master the art of glassblowing. An artisan inserts molten glass onto a hollow metal tube and blows through the tube to create a glass bubble. After the bubble is made, workers use tools and flat surfaces to shape and design the glass.
To keep glass malleable enough to work with, hardened glass is heated in a furnace. Glass melts at 1,400 - 1,600 °C (2,552 - 2,912 °F). Artisans heat the glass until it's pliable; then the maker manipulates and crafts the material to desired form.
Once the glass has been shaped and designed, it is removed from the furnace and left to cool slowly at room temperature. This cooling process is crucial to ensure that the glass retains its structural integrity and does not crack or shatter due to sudden changes in temperature.
The Romans excel in creating cameo glass, a technique of etching and carving through layers of fused colors to create raised designs on glass objects. Glass is used extensively in Europe during the Middle Ages.
From the 10th century on glass is used in stained glass windows of churches and cathedrals. By the 14th century, architects design buildings with walls of stained glass.
Glass-making is reintroduced in Ptolemaic Alexandria, Egypt ( 323 - 30 BCE). While core-formed vessels and beads remain popular, new techniques emerge due to experimentation and technological advancements.
Throughout the Hellenistic era, various innovative glass production methods are introduced, leading to creation of larger items such as tableware. Techniques such as 'slumping' involve shaping viscous glass over a mold to create dishes or specialized alchemical apparatuses.
In the 'millefiori' technique, where multicolored glass canes are sliced and fused together in a mold to produce a mosaic-like pattern. This period also sees emergence of colorless or decolored glass, which becomes highly valued.
Experiments are done and methods sought to achieve this effect, and the glass-making industry of Alexandria prospers. Today's clear glass comes from these origins.
During the Renaissance, glass making is dominated by powerful families in Italy. The most famous glass comes from Murano, an island in a chain off Venice. By the 13th century it's dominated by a podesta or magistrate from Venice.
By 1291, all glassmakers in Venice are told to relocate to Murano. Over the next century, exports start, leading to the island's renown, particularly for glass beads and mirrors. The formula for glass making is kept a secret, forcing dependence of pre-made products.
Aventurine glass is first created on Murano. A translucent glass with sparkling inclusions of gold, copper, or chromic oxide is first made in Venice in the 15th century. This establishes Venice as Europe's primary glass producer for several centuries.
Murano's glassmakers are soon among the island's most prominent citizens. By the fourteenth century, glassmakers are permitted to wear swords. They are immune from prosecution by the Venetian state, and their daughters marry into Venice's most affluent families.
Subsequently, the island gains recognition for exquisite glass chandeliers. Despite a decline in the 18h century, glassmaking remains the primary industry of Murano.
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