The Artifact: Glass Like Dough

of glass is its defining physical feature. And yet, since at least as far back as ancient Rome, there have been legends of a mysterious lost technology known as the vitrum flexila or vitrum malleabel, glass that can bend without breaking. The early medieval Spanish scholar Isadore of Seville wrote about this now occulted substance in a vast encyclopedic work called the Etymologies, which he compiled towards the beginning of the

seventh century. According to Isadore's account, during the rain of Tiberius Caesar, there was an ingenious craftsman in Rome who invented a formula for mixing clear glass so that it was flexible and pliable at room temperature. The craftsman was brought for an audience with Caesar and presented him with a gift of a glass drinking bowl. Caesar took the bowl and threw it to the floor, but unbelievably, it

did not shatter. The craftsman retrieved the bowl and showed that instead, the impact had only left a dent, as you might expect from a vessel made out of a metal like bronze. As if this wasn't amazing enough, the craftsman then produced a hammer from his tunic and proceeded to pound the dent out of the glass, restoring it to its original shape. From here i'll quote from the translation of Isadore by Stephen a Barney quote. When he had done this, Caesar said to him, does anyone else

know this method of making glass? After the craftsman swore or that no one else knew, Caesar ordered him beheaded, lest if this skill became known, gold would be regarded as mud, and the value of all metals would be reduced. And it is true that if glass vessels became unbreakable, they would be better than gold and silver. Whatever you might accept about the bloody logic of the Roman emperor, there are basic physical reasons for thinking this story is

probably not true. As common as it is now in beer bottles and car windshields, glass is in many ways an exquisite material. It's transparent, it's chemically nonreactive, it can be beautiful to look at when heated in a furnace. It can be molded into almost any shape, and it's usually made primarily of silica sand, which is abundant and cheap. But the major limitation of its usefulness has always been

that traditional silicate glass is brittle. According to Lowther wonder Check, writing for the journal Science in quote, today's glass products reach only a fraction of the predicted intrinsic strength because of their brittleness. Wonder Check explains that the main reason that glass breaks instead of bending is that mechanical energy delivered into glass, usually quote, accumulates in the vicinity of microscopic flaws and defects. This process leads to local stress concentration,

which increases with the sharpness of the tip of the flaw. Thus, the locally acting stress can be much higher than the externally applied one, and the material fails even when supporting only a low load. It doesn't seem likely to me that an inventor in the ancient world would have found a way around this brittleness, unless the substance they were

talking about was not actually glass. Aside from the brute physical implausibility of this story, there's some other compelling reasons to think it's proudly nothing more than a misinterpreted rumor or fantasy. The earliest versions of the legend crop up in first century CE sources like the Satiricon of Petronius,

where it appears in the explicit context of fiction. The Satiricon is a sort of absurdest comic novel, involving lots of crude sexual humor and vignettes about werewolves and cannibalism. The story of flexible glass is also told by Plenty of the Elder in his first century Encyclopedia The Natural History. One of Isadore's sources, Plenty rights that after the invention was revealed quote, the manufactory of the artist was totally destroyed, we are told, in order to prevent the value of copper,

silver and gold from being depreciated. I assume the logic complied in the story is that Tiberius would have been concerned that if glass were just as malleable as gold and silver, the accumulated fortunes in those medals belonging to the rich people of Rome, including Tiberius him self would

become worthless. In other words, you could think of this as an early form of science fiction, utopian or dystopian, depending on your perspective about how a technological change could have led to a revolution in the class structure of an empire. But whatever the political implications, Plenty expresses skepticism about the story, writing that it's often repeated without much evidence. But despite Plenty's doubts, the idea of glass that could

bend without breaking had a tenacious legacy. Malleable glass would become one of the enduring obsessions of the alchemists of the Middle Ages through the Renaissance in the early Modern period, though many of them never made an explicit connection to

the story of Tiberius in the Lost Technology. In a article for Renaissance quarterly called Storied Objects, Scientific Objects and Renaissance Experiment the Case of malleable Glass, author Vera Keller writes that from around the time of the thirteenth century, the power of making alleable glass was one of the wonders attributed to the Philosopher's Stone, while on the other hand, straightforward recipes for softening glass appeared in several books of

secret knowledge between the thirteen and eighteen centuries. These recipes often claimed that if followed, glass could be made soft like leather, cloth, or even dough. Many of the recipes call for the blood of a goat, while one mentioned in a footnote by Keller calls for immersing glass in the oil of horse hoofs. Despite the great effort poured into discovering the lost secret of malleable glass, it always eluded us. However, today it looks like we may becoming

full circle on the promise of vitrum flexila. Of course, since the plastics revolution of the twentieth century, we've had lots of polymer based consumer materials that are both flexible and transparent, though that material may not always have the exact properties of silicate glass. And even when you're talking about genuine glass, there are researchers working hard to make it bend without breaking, often in the context of designing screens for current and upcoming models of phones that can

fold like a wallet without cracking their screens. These innovations in foldable glass are explored in a February article for The Verge by Sean Hollister, who quotes m I T Associate Professor of material Science J. J. Who and explaining that there are two main tricks to making glass that can bend like plastic. One of those tricks takes us back to what I mentioned already about microscopic flaws and defects in the structure of the glass that allow cracks

to propagate. Researchers are trying to prevent the formation of these tiny flaws through the use of special chemical baths and heat treatment during the manufacturing process. But the second

trick is thinness. While glass the thickness of a window pane will probably always shatter before it bends, glass less than a under in microns thick which is about the width of a human hair, can fold a surprising amount, and once the thickness is down to a few tens of microns, researchers claim that the glass can fold almost flat upon itself without breaking and without a large hinge gap, which is what the manufacturers of these phones ultimately want.

And one of my favorite details is that some of the new flexible glass could be created with alternative chemical compositions, by making the glass not out of silica, but out of materials like aluminum oxide, which in its condensed crystalline form is what makes a Sapphire. Tune into new editions of the Artifact every Wednesday, hosted by either Robert or myself. As always, you can email us at contact at stuff to Blow your Mind dot com. Stuff to Blow Your

Mind is production of iHeartRadio. For more podcasts from my Heart Radio, visit the iHeart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.