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The Strange Life of Glass

This essential substance has a history—and future—that’s far from clear.

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Glass is perhaps the most frequently overlooked material in history. It is essential to our lives, more so even than plastic. A world without glass is more unimaginable to me than terraforming Mars (practically an impossibility, most scientists agree). Without this banal marvel, you wouldn’t be able to use a touch-screen phone, switch on a lamp, look out a window, put on your glasses, sip from that bottle on your nightstand. You wouldn’t be able to receive emails or phone calls or access the Internet.

In an article for The Atlantic, glass is called “humankind’s most important material.” Douglas Main writes, “To reach you, these words were encoded into signals of light moving about 125,000 miles per second through fiber-optic cables,” which climb up mountains, creep under oceans, making tracks through cities and countries, all around the globe. The glass within is thinner than a human hair and “30 times more transparent than the purest water.” Glass allows us to see and be seen, hear and be heard, to illuminate our rooms and lives and thoughts.

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From a thermodynamic point of view, glass wants to become a solid. 

But glass is a funny material, partially because the word itself is a general term, one that refers not to a specific chemical formula but a substance that can be manufactured according to an “endless number of recipes.” Yet when we say “glass,” we understand it to mean something quite specific: It’s a type of material that is hard and brittle yet capable of being turned viscous and mobile with enough heat. Sometimes glass is erroneously characterized as a liquid, because even in its cooled form, it does move (albeit very slowly). Glass is not solid like rocks are solid because its molecules aren’t as rigidly organized as any material with a crystalline structure. Diamonds have a crystalline structure, as does ice and hardened honey, but glass does not. While more dependable than a sheet of ice, glass is, on a molecular level, a lot less ordered.

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In materials science, glass is typically considered an “amorphous solid” or as John C. Mauro puts it, glass is a “nonbinary material,” neither liquid nor solid.

A former researcher and inventor and current engineering and materials science professor at Penn State University, Mauro has been fascinated by glass ever since he visited the Corning Museum of Glass in New York as a 6-year-old. He recalls being “captivated” by the colors and shapes. These days, he knows more than almost anyone about how glass functions, yet he retains a sense of awe for the substance. “Glass is its own thing,” he says. “It breaks the mold.”

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HANDLE WITH CARE: The seemingly mundane and inert material we call glass turns out to be anything but. On a molecular level, it behaves more like a liquid, but from a thermodynamic point of view, it wants to become a solid. Photo by Ingrid Maasik / Shutterstock.

From a thermodynamic point of view, he explains, glass wants to become a solid. When observed on a molecular level, glass behaves more like a viscous liquid than a solid, yet we experience it like a solid because of how slowly it shifts. “Philosophically, it’s interesting that we’re observing glass at all,” Mauro says. “We see through it, when we’re looking at something else.” Yet there, right under our noses, is a scientific marvel—a material that behaves in a fascinatingly unique way, a substance that resists easy categorization. It makes up our lenses, our microscopes, our telescopes, our screens, our glasses. It allows us to see the world clearly, yet so rarely do we really see glass.

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It’s this disappearing act that makes glass a strange vessel for beauty. It defies what we’re taught as children about matter, that there’s three states: solid, liquid, gas. It’s not rare by any stretch of the imagination. But glass is special despite all that.

Glass is mainly a manufactured substance. While some natural glass does exist, like obsidian and tektite, the vast majority of glass has been cooked over fires we built. As far as we can tell, glass manufacturing dates back to the Bronze Age somewhere in Mesopotamia. Some 4,000 years ago, human beings began melting silica (sand or crushed quartz) and mixing it with small amounts of limestone and soda ash. According to Pliny, the invention of glass was a happy accident. The Roman historian thought it happened at a cookout on a beach with some Phoenician sailors, but since no cookfire could get hot enough to melt sand, this seems doubtful. Contemporary historians believe glass could have been discovered through experiments with ceramics or metalworking—two early crafts that called for hotter ovens and longer firing times than any loaf of bread or leg of goat.

Out of all the players in the material world, glass is the ultimate trickster. 

The oldest known glass objects were used and handled like the lesser cousins of precious stones, worked cold rather than hot, chiseled rather than melted. People cut them, ground them, and set them in jewelry. At some point, our distant ancestors figured out how to cast glass in molds to produce vessels. Before anyone was blowing glass, artisans were creating glass mosaics, small mirrors, and a number of different types of vessels that could be used to store wine, perfume, drugs, and other valuable substances.

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Around year zero, glass went big-time, thanks to the Romans and their regimented methods of production. Glass-blowing (a technique imported from Syria) enabled workmen (often enslaved people) to create cups and bowls much more quickly than any of the previous methods of glasswork. Glass cups could be purchased cheaply at market, and soon glass rivaled pottery in its popularity for the average Roman. Artists began experimenting more with form, creating two-faced Janus-head vases and wine bottles decorated with scenes of carnal pleasure. Builders began using glass to make windows, but since the glass was fairly murky and thick, the purpose of adding glass was probably less about illumination and more about security and insulation. We’ve found evidence of glass windows throughout Rome and the surrounding cities, including in the luxuriously tiled, beautifully preserved bathhouses of Pompeii.

The age of the lens is difficult to pinpoint, for lenses pre-date the year zero by a decent span. Optics came into its own as an area of study at the end of the first millennia in the Islamic world, where mathematicians and scientists were making great leaps in the understanding and manipulation of light. During the Renaissance, philosophers, scientists, and thinkers were all using lenses to examine the physical world—both the stars above (with the invention of the telescope in 1608) and the ground below (after the introduction of the microscope in 1625). Glass has long been seen as a material that grants literal illumination, but it’s worth remembering that glass laid the groundwork for much of our metaphorical enlightenment too.

The Enlightenment was also an era that birthed the phantasmagoria, a form of theatrical entertainment that was either horrifying or hopeful, depending on how one chose to see it. 

Glass sharpens our vision but not necessarily our understanding.

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Phantasmagoria were wild, eerie events during which guests paid to be terrorized by moving images of spirits, demons, and other frightening figures that were projected onto walls, smoke, or semi-transparent screens. This spiritually tinged form of proto-cinema was made possible by a combination of inventions new and old, including magic lanterns, magnifying lenses, Zograscopes, pepper’s ghosts, and other glass-based tools that could be used to manipulate light and sight.

The first phantasmagorias took place in the 1790s in a theater in post-Revolution Paris to the eerie background tunes of a glass harmonica. After waiting for a few moments in complete darkness, the audience began to see shapes emerge from the air, spectral figures that appeared to float and glide. Pale and otherworldly, these ghosts spoke, shouted, and cried. One, the Bleeding Nun, approached menacingly before retreating. Later versions of the phantasmagoria would involve the ghosts of recently deceased public figures, supposedly wrangled into submission by the powers of science. For that’s how these shows were billed: as the intersection between science and religion, faith, and enlightenment. They were horrible, but also a real hoot.

We’re still begging to be both fooled and enlightened. Humans love a spectacle. Out of all the players in the material world, I think glass is the ultimate trickster. Although glass can illuminate rooms and lives, it can also distort reality and obscure the truth. Much like how photography can appear as a record of true events while cropping out essential context, glass sharpens our vision but not necessarily our understanding.

Contemporary life relies on glass more than most of us realize; it’s not just in our windshields and windows, it’s also in the fiber-optic cables that run under our feet, pulsing with meaning. “Right now we’re looking at each other via glass screens,” Mauro said during our interview, making me intensely aware of the tenuous nature of our connection. We were speaking over Zoom, a service that allows people to video chat over the Internet, using our respective laptops in our rooms hundreds of miles apart. He continued, “We wouldn’t have information screens without glass. All of this is being transmitted via light signal through really thin pieces of glass we call fiber optics.” Without glass, he said, we wouldn’t have modern architecture, artificial lighting, natural lighting, cars, and most crucially, so much information.

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Mauro stresses the benefits of glass. It enables us to store vaccines, examine cells, and gaze at the stars. But he argues that glass is, like all technology, “neutral” at its core. “When I think about fiber optics, I think about all the good things it’s done to enable communication, but it’s also done a lot of harm,” he said. People use social media to “spread lies and hate.”

We use glass to tell our individual truths, but we can also use it to create false narratives. I wouldn’t have been able to get the coronavirus vaccine without glass vials, but we also wouldn’t have seen such rapidfire spread of anti-vaccine propaganda if we didn’t have glass screens in our pockets. Without glass tubes, German glassblower Heinrich Geissler wouldn’t have been able to observe cathode rays, Ernest Rutherford wouldn’t have been able to discover the power contained in an atom’s nucleus, we wouldn’t have nuclear reactors or bombs. We wouldn’t know that, when an atomic bomb goes off, it has the power to turn sand into glass, raining asteroidlike shards on the ground for people to find decades later. Maybe we wouldn’t be so uncertain, so unstable in our convictions.

While I agree with much of what Mauro says, I don’t know if glass is truly neutral or if any technology can be said to be neutral. I think calling it neutral is a shorthand, like calling glass a solid. It’s far more ambiguous than that. Technology isn’t inert. It’s not a stone; it’s a language. And like a language, we must accept its many uses. We can say prayers; we can tell lies. Sometimes, we do it in the same breath.

But that’s human history. It’s a chain of events, one leading to another, sometimes ending in disaster, sometimes ending in beauty. When you look at it from one angle, it can appear full of beauty, prisms of color dancing across eons. From another, it’s so much hellfire.

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Katy Kelleher is an art, design, nature, and science writer living in the woods of Maine. She’s a frequent contributor to The Paris Review, and her work has appeared in The New York Times, The Guardian, American Scholar, Town & Country, Vogue, Harper’s Bazaar, Jezebel, and others.

From The Ugly History of Beautiful Things: Essays on Desire and Consumption by Katy Kelleher. Copyright © 2023 by Katy Kelleher. Reprinted by permission of Simon & Schuster, Inc.

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Lead image: SVPanteon / Shutterstock

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