Everything Everywhere Daily: History, Science, Geography & More - The History of Glass

Starting point is 00:00:00 It began as a rare luxury valued alongside precious stones and guarded by skilled craftsmen. Over thousands of years, it transformed architecture, science, art, and medicine. It allowed people to see further into space, deeper into the microscopic world, and even transmit information around the planet at the speed of light. Yet, at its core, it is a deceptively simple mixture of sand, minerals, and heat. Learn more about the history of glass on this episode of Everything Everywhere Daily. This episode is brought to you by Accenture. When your advertising operations fall out of sync, everything else follows.

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Starting point is 00:01:34 New episodes week over week. Watch the Hulu original series Furious, now streaming only on Hulu on Disney Plus. Glass is one of humanity's oldest synthetic materials and one of its most important. It began as a rare substance used to imitate gemstones and eventually became an ordinary material used for windows, bottles, mirrors, lenses, and many other applications. Its history is closely tied to advances in chemistry, furnace design, manufacturing, and trade. But before we get into the history of glass, we should address the very important question, what is glass? Glass is an amorphous solid, meaning its atoms are arranged irregularly rather than in the repeating crystal structure found in minerals such as quartz. Most common glass

Starting point is 00:02:27 is made primarily from just three ingredients. Silica, which is usually obtained from sand and forms the basic structure. Soda, traditionally derived from the mineral natron or plant ashes, which lowers the temperature at which silica melts, and lime, which is usually derived from limestone, and makes the finished glass more chemically stable and resistant to water. Pure silica melts at approximately 1,700 degrees Celsius or 3,92 degrees Fahrenheit, far beyond the capabilities of most ancient furnaces. Adding soda made glass production possible at lower temperatures,

Starting point is 00:03:06 while lime prevented the resulting material from slowly dissolving deteriorating. And here I should address an urban myth that glass is actually a very, very slow-flowing liquid. This is not true. Glass is a solid, as anyone who has cut themselves on it can attest. The reason for the glass is a liquid myth was that in very old stained glass windows, the glass was thicker at the bottom than at the top. Some took this as evidence that glass was slowly flowing over time. In reality, it was an artifact of the production methods of the time, resulting in uneven glass thickness, and the thicker parts were put at the bottom for stability. While most glass that we're familiar with was manufactured, glass can also form naturally.

Starting point is 00:03:56 Obsidian is volcanic glass created when lava cools too quickly to crystallize. Lightning strikes confuse sand into branching glass structures called folgerites. Meteorite impacts can also produce natural glass. Obsidian was one of the most valuable substances of the Stone Age. Because it fractures into extremely sharp edges, prehistoric people used it to make knives, scrapers, spear points, and arrowheads. The precise origin of glass making remains uncertain. Early glass probably emerged gradually from experiments with ceramic glazes and metalworking slag rather than from a single dramatic invention. Small glass beads in accidental glassy materials appeared in Mesopotamia and Egypt during the 3rd millennium

Starting point is 00:04:42 BC. Large-scale, deliberate production developed around the middle of the second millennium BC, probably in northern Mesopotamia, Syria, and Egypt. Evidence suggests that glass vessels were being manufactured by approximately the 16th or 15th century BC. The traditional story told by the Roman writer Pliny the Elder claimed that Phoenician sailors accidentally discovered glass when blocks of soda used to support cooking pots fused with beach sand. And this story is almost certainly a legend. The temperatures of an ordinary cooking fire would have been insufficient to produce useful glass, and archaeological evidence indicates a much more gradual technological development.

Starting point is 00:05:25 Early glass was seldom clear. It was usually opaque or translucent and colored blue, green, red, yellow, or white. Deep blue glass was especially prized because it really was. resembled Lopas-Lazui, a valuable stone imported from Afghanistan. Ancient descriptions sometimes treated glass as a kind of artificial or flowing stone. Glass making was an elite craft. Furnaces were difficult to operate, raw material had to be carefully selected, and colored glass required specialized knowledge. Cobalt produced blue glass, copper produced blue, green, or red, manganese could produce purple, and antimony compounds were used for opaque, white, or yellow, and yellow.

Starting point is 00:06:06 yellow glass. During the first millennium BC, glass making revived across the eastern Mediterranean after the Bronze Age collapse. Glass beads and vessels circulated through Phoenician, Greek, Persian, Etruscan, and other trading networks. Most glass objects remained relatively expensive. Techniques included casting, core forming, cutting, grinding, mosaic work, and pressing glass into molds. Greek craftsmen became increasingly skilled at producing bowls by casting glass into mold, molds, and then cutting or polishing the surfaces. Some vessels imitated carved stone, metalwork, or precious gemstones. One of the most famous glass objects in the ancient world was the coffin of Alexander the Great, made after the original gold coffin was melted down.

Starting point is 00:06:55 Glass was probably not independently discovered in China. Glass was an imported luxury material during the late, second, or early first millennium BC. The earliest secure, purely identified glass objects in China date mainly from the warring states period for monthly 475 to 221 BC, including beads and small ornaments influenced by West and Central Asian glassmaking. Imported Roman and later Sasanian glass became more common during the Han dynasty and the centuries that followed, arriving via the Silk Road and maritime trade. Large-scale glassmaking, however, never became as important to Chinese culture as ceramics or porcelain. The major advance in ancient glass production was the development of glass blowing.

Starting point is 00:07:43 Glass blowing probably developed in the Levant during the first century BC. At some point, a craftsman gathered molten glass at the end of a hollow iron blowpipe and inflated it by blowing through the tube. And this transformed the industry. Earlier glass products required laborious casting, core forming, grinding, and polishing. A skilled glass blouse, lower, however, could create a hollow vessel in a matter of minutes. Glass could be blown freely, inflated in a mold, stretched in a tube, decorated or shaped with just simple hand tools. The technique spread rapidly through the Roman world during the first century. The Romans didn't invent glass, but they turned it into a widely available commodity. Large furnaces in Egypt and the

Starting point is 00:08:28 Eastern Mediterranean produce substantial blocks or slabs of raw glass, which were then transported into secondary workshops throughout the empire. There, glass workers remelted and shaped the material into glass objects. Roman glass included drinking cups, perfume bottles, jugs, bowls, jewelry, and many other items. Glass containers became especially useful because they did not absorb the smells or flavors as readily as pottery. The Romans produced both colored and nearly colorless glass. Iron impurities naturally gave glass a blue-green tint.

Starting point is 00:09:04 adding substances such as manganese could neutralize some of the color, although ancient glass was rarely as perfectly clear as modern glass. The Romans were also the first people to use glass in windows. Early window glass was often cast or rolled in relatively small, thick sheets. It tended to be uneven, cloudy, and distorted. Window glass remained expensive, but it allowed architects to admit light while keeping out wind rained and cold. This was especially valuable in bathhouses, where large interior spaces had to remain warm. The collapse of the Western Roman Empire didn't end glassmaking,

Starting point is 00:09:43 but it fragmented the industry. Workshops continued in the Byzantine Empire, the Islamic world, Western Europe, and now parts of Asia. The Byzantine Empire preserved many Roman techniques, including blowing, molding, cutting, and mosaic production. After the Islamic conquest of the 7th century, glassmaking flourished in Syria, Egypt, Mesopotamia, Persia, and other regions. Islamic glassmakers inherited Roman and Byzantine traditions, but developed distinctive decorative methods.

Starting point is 00:10:13 Glass reached South Asia in antiquity through both local experimentation and international trade. Indian craftsmen became especially skilled at producing beads, bengals, decorative glass, and small vessels. South Asian glass circulated throughout the Indian Ocean Trade Network into Southeast Asia and even East Africa. In medieval Europe, glass was produced in forested regions where wood supplied both furnace fuel and ash.

Starting point is 00:10:40 These workshops made bottles, drinking vessels, beads, and window glass. Most medieval household glass, known as forest glass, was greenish because of impurities in the raw materials. The great medieval contribution

Starting point is 00:10:54 to architectural glass was the stained glass window. Colored glass had existed since antiquity, but medieval church builders combine pieces of colored glass into large and narrative and symbolic compositions. Individual pieces were fitted into lead strips called cames. They were then joined together and supported by iron frameworks. Details such as faces, folds and clothing and inscriptions could be painted onto the glass with pigments and then fired. Romanesque and Gothic churches use stained glass to fill interiors with colored light. The expansion of Gothic architecture in

Starting point is 00:11:29 the 12th and 13th centuries, with pointed arches, rib vaults, and flying buttresses, allowed walls to contain much larger windows. Venice emerged as Europe's leading center of luxury glassmaking during the late Middle Ages and Renaissance. Venetian glassmakers benefited from commercial links with the Byzantine and Islamic worlds, access to imported raw materials, and a wealthy market for luxury goods. In 1291, Venetian authorities ordered that all glass furnaces be moved to the nearby island of Morano to prevent fires. From approximately 1,500 to the early 18th century, Venice was Europe's dominant supplier of fine luxury glass. The Venetian government attempted to protect technical knowledge by restricting

Starting point is 00:12:13 glass workers' movements, but many craftsmen emigrated and established Venetian-style production elsewhere. The scientific revolution depended heavily on improved glass. Lenses had been used as magnifying devices in the Middle Ages, and eyeglasses appeared in Italy by the late 13th century. Early spectacles corrected far-sightedness and used convex lenses. Concave lenses for near-sightedness followed soon after. The telescope appeared in the Netherlands around 1608. Galileo improved the instrument and used it to observe mountains on the moon, Jupiter's moons, and the faces of Venus. The compound microscope developed around the same period. Robert Hook used microscopes to examine insects, plants, and other materials, while Anthony Vuonlewun-Hook carefully made single-lens microscopes

Starting point is 00:13:00 that revealed microorganisms. These discoveries depended on the ability to produce glass that was reasonably clear, homogeneous, and accurately shaped. English glassmaker George Ravenscroft patented an improved lead glass by 1674. By adding lead oxide, manufacturers produce glass with a high refractive index, notable brilliance, and characteristic ringing sound. The Industrial Revolution transformed glass from a skilled workshop product into a major industrial material. Coal-fired furnaces provided more consistent heat than wood. Steam power operated grinding, cutting, and polishing machinery. Improved transportation made it easier to move sand, limestone, coal, finished bottles, and glass windows. Chemists gained better control over

Starting point is 00:13:48 composition. The LeBlanc process developed in the late 18th century, created soda ash from salt, and helped replace limited natural supplies of natron and plant ash. The solvay process developed during the 19th century provided a cleaner and more economical use of sodium carbonate. Mechanical processing appeared in the early 19th century. A measured amount of molten glass was placed in a mold and pressed into a shape with a plunger. pressed glass allowed manufacturers to mass produce bowls, dishes, and other decorative objects that resembled expensive cut glass. It brought ornamental glassware within the reach of the middle class and working glass customers. Early plate glass was made by casting molten glass onto a metal

Starting point is 00:14:33 table, rolling it flat, and then grinding and polishing both sides. The process produced high-quality pains, but it was slow, wasteful, and expensive. Nevertheless, industrial plate glass, made possible the great display windows of 19th century department stores and exhibition buildings. The Crystal Palace constructed for London's Great Exhibition of 1851 demonstrated the architectural potential of pre-fabricated iron and glass. Michael Owens developed a commercially successful automatic bottle-making machine in the early 20th century. Automatic machines could produce bottles much faster and more consistently than teams of glass blowers. Cheap bottles transform beverages.

Starting point is 00:15:14 medicine and food preservation. Standardized bottles also encourage branding, labeling, and mass distribution. Perhaps the most important modern development in flat glass production was the float process. Sir Alistair Pilkington and Kenneth Bickerstaff developed the commercially successful method in Britain during the 1950s. Moulton glass flows continuously from a furnace onto a bath of molten tin. because glass is lighter than tin and doesn't mix with it, it floats and spreads into a smooth ribbon. Gravity and surface tension create surfaces that are naturally flat and parallel. Float glass eliminated much of the grinding and polishing required by earlier plate glass methods. It made large, clear, distortion-free panes economical on an enormous scale.

Starting point is 00:16:05 Today, glass can be found almost everywhere. Durable, scratch-resistant glass is in your smartphone. phone. Glass fiber optic cables are the backbone in the internet, and glass is still a fundamental part of almost every home. There's a lot more to be said about glass, but it has had a remarkable journey for something that was probably discovered by accident thousands of years ago. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Austin Otkin and Cameron Kiefer. My big thanks go to everyone who supports the show over on Patreon. your support helps make this podcast possible.

Starting point is 00:16:43 And I also want to remind everyone about the community groups on Facebook and Discord. That's where everything happens that's outside the podcast. And links to those are available in the show notes. As always, if you leave a review on any major podcast app or in the above community groups, you two can have it read in the show.

Everything Everywhere Daily: History, Science, Geography & More - The History of Glass

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