Speaker 1: Welcome to Stuff to Blow Your Mind, a production of
Speaker 1: iHeart Radio. Hi. My name is Joe McCormick. And this
Speaker 1: is the Artifact, a short form series from Stuff to
Speaker 1: Blow Your Mind, focusing on particular objects, ideas, and moments
Speaker 1: in time. Glass breaks. Apart from its transparency, the brittleness
Speaker 1: of glass is its defining physical feature. And yet, since
Speaker 1: at least as far back as ancient Rome, there have
Speaker 1: been legends of a mysterious lost technology known as the
Speaker 1: vitrum flexila or vitrum malleabel, glass that can bend without breaking.
Speaker 1: The early medieval Spanish scholar Isadore of Seville wrote about
Speaker 1: this now occulted substance in a vast encyclopedic work called
Speaker 1: the Etymologies, which he compiled towards the beginning of the
Speaker 1: seventh century. According to Isadore's account, during the rain of
Speaker 1: Tiberius Caesar, there was an ingenious craftsman in Rome who
Speaker 1: invented a formula for mixing clear glass so that it
Speaker 1: was flexible and pliable at room temperature. The craftsman was
Speaker 1: brought for an audience with Caesar and presented him with
Speaker 1: a gift of a glass drinking bowl. Caesar took the
Speaker 1: bowl and threw it to the floor, but unbelievably, it
Speaker 1: did not shatter. The craftsman retrieved the bowl and showed
Speaker 1: that instead, the impact had only left a dent, as
Speaker 1: you might expect from a vessel made out of a
Speaker 1: metal like bronze. As if this wasn't amazing enough, the
Speaker 1: craftsman then produced a hammer from his tunic and proceeded
Speaker 1: to pound the dent out of the glass, restoring it
Speaker 1: to its original shape. From here i'll quote from the
Speaker 1: translation of Isadore by Stephen a Barney quote. When he
Speaker 1: had done this, Caesar said to him, does anyone else
Speaker 1: know this method of making glass? After the craftsman swore
Speaker 1: or that no one else knew, Caesar ordered him beheaded,
Speaker 1: lest if this skill became known, gold would be regarded
Speaker 1: as mud, and the value of all metals would be reduced.
Speaker 1: And it is true that if glass vessels became unbreakable,
Speaker 1: they would be better than gold and silver. Whatever you
Speaker 1: might accept about the bloody logic of the Roman emperor,
Speaker 1: there are basic physical reasons for thinking this story is
Speaker 1: probably not true. As common as it is now in
Speaker 1: beer bottles and car windshields, glass is in many ways
Speaker 1: an exquisite material. It's transparent, it's chemically nonreactive, it can
Speaker 1: be beautiful to look at when heated in a furnace.
Speaker 1: It can be molded into almost any shape, and it's
Speaker 1: usually made primarily of silica sand, which is abundant and cheap.
Speaker 1: But the major limitation of its usefulness has always been
Speaker 1: that traditional silicate glass is brittle. According to Lowther wonder Check,
Speaker 1: writing for the journal Science in quote, today's glass products
Speaker 1: reach only a fraction of the predicted intrinsic strength because
Speaker 1: of their brittleness. Wonder Check explains that the main reason
Speaker 1: that glass breaks instead of bending is that mechanical energy
Speaker 1: delivered into glass, usually quote, accumulates in the vicinity of
Speaker 1: microscopic flaws and defects. This process leads to local stress concentration,
Speaker 1: which increases with the sharpness of the tip of the flaw. Thus,
Speaker 1: the locally acting stress can be much higher than the
Speaker 1: externally applied one, and the material fails even when supporting
Speaker 1: only a low load. It doesn't seem likely to me
Speaker 1: that an inventor in the ancient world would have found
Speaker 1: a way around this brittleness, unless the substance they were
Speaker 1: talking about was not actually glass. Aside from the brute
Speaker 1: physical implausibility of this story, there's some other compelling reasons
Speaker 1: to think it's proudly nothing more than a misinterpreted rumor
Speaker 1: or fantasy. The earliest versions of the legend crop up
Speaker 1: in first century CE sources like the Satiricon of Petronius,
Speaker 1: where it appears in the explicit context of fiction. The
Speaker 1: Satiricon is a sort of absurdest comic novel, involving lots
Speaker 1: of crude sexual humor and vignettes about werewolves and cannibalism.
Speaker 1: The story of flexible glass is also told by Plenty
Speaker 1: of the Elder in his first century Encyclopedia The Natural History.
Speaker 1: One of Isadore's sources, Plenty rights that after the invention
Speaker 1: was revealed quote, the manufactory of the artist was totally destroyed,
Speaker 1: we are told, in order to prevent the value of copper,
Speaker 1: silver and gold from being depreciated. I assume the logic
Speaker 1: complied in the story is that Tiberius would have been
Speaker 1: concerned that if glass were just as malleable as gold
Speaker 1: and silver, the accumulated fortunes in those medals belonging to
Speaker 1: the rich people of Rome, including Tiberius him self would
Speaker 1: become worthless. In other words, you could think of this
Speaker 1: as an early form of science fiction, utopian or dystopian,
Speaker 1: depending on your perspective about how a technological change could
Speaker 1: have led to a revolution in the class structure of
Speaker 1: an empire. But whatever the political implications, Plenty expresses skepticism
Speaker 1: about the story, writing that it's often repeated without much evidence.
Speaker 1: But despite Plenty's doubts, the idea of glass that could
Speaker 1: bend without breaking had a tenacious legacy. Malleable glass would
Speaker 1: become one of the enduring obsessions of the alchemists of
Speaker 1: the Middle Ages through the Renaissance in the early Modern period,
Speaker 1: though many of them never made an explicit connection to
Speaker 1: the story of Tiberius in the Lost Technology. In a
Speaker 1: article for Renaissance quarterly called Storied Objects, Scientific Objects and
Speaker 1: Renaissance Experiment the Case of malleable Glass, author Vera Keller
Speaker 1: writes that from around the time of the thirteenth century,
Speaker 1: the power of making alleable glass was one of the
Speaker 1: wonders attributed to the Philosopher's Stone, while on the other hand,
Speaker 1: straightforward recipes for softening glass appeared in several books of
Speaker 1: secret knowledge between the thirteen and eighteen centuries. These recipes
Speaker 1: often claimed that if followed, glass could be made soft
Speaker 1: like leather, cloth, or even dough. Many of the recipes
Speaker 1: call for the blood of a goat, while one mentioned
Speaker 1: in a footnote by Keller calls for immersing glass in
Speaker 1: the oil of horse hoofs. Despite the great effort poured
Speaker 1: into discovering the lost secret of malleable glass, it always
Speaker 1: eluded us. However, today it looks like we may becoming
Speaker 1: full circle on the promise of vitrum flexila. Of course,
Speaker 1: since the plastics revolution of the twentieth century, we've had
Speaker 1: lots of polymer based consumer materials that are both flexible
Speaker 1: and transparent, though that material may not always have the
Speaker 1: exact properties of silicate glass. And even when you're talking
Speaker 1: about genuine glass, there are researchers working hard to make
Speaker 1: it bend without breaking, often in the context of designing
Speaker 1: screens for current and upcoming models of phones that can
Speaker 1: fold like a wallet without cracking their screens. These innovations
Speaker 1: in foldable glass are explored in a February article for
Speaker 1: The Verge by Sean Hollister, who quotes m I T
Speaker 1: Associate Professor of material Science J. J. Who and explaining
Speaker 1: that there are two main tricks to making glass that
Speaker 1: can bend like plastic. One of those tricks takes us
Speaker 1: back to what I mentioned already about microscopic flaws and
Speaker 1: defects in the structure of the glass that allow cracks
Speaker 1: to propagate. Researchers are trying to prevent the formation of
Speaker 1: these tiny flaws through the use of special chemical baths
Speaker 1: and heat treatment during the manufacturing process. But the second
Speaker 1: trick is thinness. While glass the thickness of a window
Speaker 1: pane will probably always shatter before it bends, glass less
Speaker 1: than a under in microns thick which is about the
Speaker 1: width of a human hair, can fold a surprising amount,
Speaker 1: and once the thickness is down to a few tens
Speaker 1: of microns, researchers claim that the glass can fold almost
Speaker 1: flat upon itself without breaking and without a large hinge gap,
Speaker 1: which is what the manufacturers of these phones ultimately want.
Speaker 1: And one of my favorite details is that some of
Speaker 1: the new flexible glass could be created with alternative chemical compositions,
Speaker 1: by making the glass not out of silica, but out
Speaker 1: of materials like aluminum oxide, which in its condensed crystalline
Speaker 1: form is what makes a Sapphire. Tune into new editions
Speaker 1: of the Artifact every Wednesday, hosted by either Robert or myself.
Speaker 1: As always, you can email us at contact at stuff
Speaker 1: to Blow your Mind dot com. Stuff to Blow Your
Speaker 1: Mind is production of iHeartRadio. For more podcasts from my
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