1 00:00:03,279 --> 00:00:05,640 Speaker 1: Welcome to Stuff to Blow Your Mind, a production of 2 00:00:05,640 --> 00:00:11,560 Speaker 1: iHeart Radio. Hi. My name is Joe McCormick. And this 3 00:00:11,800 --> 00:00:14,840 Speaker 1: is the Artifact, a short form series from Stuff to 4 00:00:14,880 --> 00:00:19,120 Speaker 1: Blow Your Mind, focusing on particular objects, ideas, and moments 5 00:00:19,120 --> 00:00:26,759 Speaker 1: in time. Glass breaks. Apart from its transparency, the brittleness 6 00:00:26,760 --> 00:00:30,320 Speaker 1: of glass is its defining physical feature. And yet, since 7 00:00:30,360 --> 00:00:33,040 Speaker 1: at least as far back as ancient Rome, there have 8 00:00:33,120 --> 00:00:36,919 Speaker 1: been legends of a mysterious lost technology known as the 9 00:00:37,040 --> 00:00:43,680 Speaker 1: vitrum flexila or vitrum malleabel, glass that can bend without breaking. 10 00:00:44,680 --> 00:00:48,280 Speaker 1: The early medieval Spanish scholar Isadore of Seville wrote about 11 00:00:48,320 --> 00:00:52,400 Speaker 1: this now occulted substance in a vast encyclopedic work called 12 00:00:52,479 --> 00:00:55,840 Speaker 1: the Etymologies, which he compiled towards the beginning of the 13 00:00:55,880 --> 00:01:00,200 Speaker 1: seventh century. According to Isadore's account, during the rain of 14 00:01:00,240 --> 00:01:04,080 Speaker 1: Tiberius Caesar, there was an ingenious craftsman in Rome who 15 00:01:04,160 --> 00:01:08,120 Speaker 1: invented a formula for mixing clear glass so that it 16 00:01:08,200 --> 00:01:12,800 Speaker 1: was flexible and pliable at room temperature. The craftsman was 17 00:01:12,840 --> 00:01:15,720 Speaker 1: brought for an audience with Caesar and presented him with 18 00:01:15,760 --> 00:01:19,280 Speaker 1: a gift of a glass drinking bowl. Caesar took the 19 00:01:19,319 --> 00:01:23,759 Speaker 1: bowl and threw it to the floor, but unbelievably, it 20 00:01:23,800 --> 00:01:27,679 Speaker 1: did not shatter. The craftsman retrieved the bowl and showed 21 00:01:27,720 --> 00:01:31,080 Speaker 1: that instead, the impact had only left a dent, as 22 00:01:31,120 --> 00:01:33,160 Speaker 1: you might expect from a vessel made out of a 23 00:01:33,200 --> 00:01:37,240 Speaker 1: metal like bronze. As if this wasn't amazing enough, the 24 00:01:37,280 --> 00:01:41,240 Speaker 1: craftsman then produced a hammer from his tunic and proceeded 25 00:01:41,240 --> 00:01:45,039 Speaker 1: to pound the dent out of the glass, restoring it 26 00:01:45,120 --> 00:01:48,600 Speaker 1: to its original shape. From here i'll quote from the 27 00:01:48,640 --> 00:01:52,840 Speaker 1: translation of Isadore by Stephen a Barney quote. When he 28 00:01:52,880 --> 00:01:56,120 Speaker 1: had done this, Caesar said to him, does anyone else 29 00:01:56,200 --> 00:01:59,960 Speaker 1: know this method of making glass? After the craftsman swore 30 00:02:00,120 --> 00:02:03,880 Speaker 1: or that no one else knew, Caesar ordered him beheaded, 31 00:02:04,600 --> 00:02:08,600 Speaker 1: lest if this skill became known, gold would be regarded 32 00:02:08,639 --> 00:02:12,239 Speaker 1: as mud, and the value of all metals would be reduced. 33 00:02:12,600 --> 00:02:15,919 Speaker 1: And it is true that if glass vessels became unbreakable, 34 00:02:16,240 --> 00:02:25,600 Speaker 1: they would be better than gold and silver. Whatever you 35 00:02:25,680 --> 00:02:28,400 Speaker 1: might accept about the bloody logic of the Roman emperor, 36 00:02:28,720 --> 00:02:31,880 Speaker 1: there are basic physical reasons for thinking this story is 37 00:02:31,880 --> 00:02:35,320 Speaker 1: probably not true. As common as it is now in 38 00:02:35,440 --> 00:02:38,720 Speaker 1: beer bottles and car windshields, glass is in many ways 39 00:02:38,760 --> 00:02:44,639 Speaker 1: an exquisite material. It's transparent, it's chemically nonreactive, it can 40 00:02:44,680 --> 00:02:47,760 Speaker 1: be beautiful to look at when heated in a furnace. 41 00:02:47,800 --> 00:02:51,240 Speaker 1: It can be molded into almost any shape, and it's 42 00:02:51,320 --> 00:02:55,160 Speaker 1: usually made primarily of silica sand, which is abundant and cheap. 43 00:02:56,160 --> 00:02:59,040 Speaker 1: But the major limitation of its usefulness has always been 44 00:02:59,120 --> 00:03:04,119 Speaker 1: that traditional silicate glass is brittle. According to Lowther wonder Check, 45 00:03:04,240 --> 00:03:08,880 Speaker 1: writing for the journal Science in quote, today's glass products 46 00:03:08,919 --> 00:03:12,920 Speaker 1: reach only a fraction of the predicted intrinsic strength because 47 00:03:13,120 --> 00:03:17,320 Speaker 1: of their brittleness. Wonder Check explains that the main reason 48 00:03:17,360 --> 00:03:21,160 Speaker 1: that glass breaks instead of bending is that mechanical energy 49 00:03:21,200 --> 00:03:25,160 Speaker 1: delivered into glass, usually quote, accumulates in the vicinity of 50 00:03:25,280 --> 00:03:30,840 Speaker 1: microscopic flaws and defects. This process leads to local stress concentration, 51 00:03:31,160 --> 00:03:35,040 Speaker 1: which increases with the sharpness of the tip of the flaw. Thus, 52 00:03:35,120 --> 00:03:37,760 Speaker 1: the locally acting stress can be much higher than the 53 00:03:37,800 --> 00:03:41,760 Speaker 1: externally applied one, and the material fails even when supporting 54 00:03:41,840 --> 00:03:44,960 Speaker 1: only a low load. It doesn't seem likely to me 55 00:03:45,160 --> 00:03:47,600 Speaker 1: that an inventor in the ancient world would have found 56 00:03:47,600 --> 00:03:50,640 Speaker 1: a way around this brittleness, unless the substance they were 57 00:03:50,640 --> 00:03:55,120 Speaker 1: talking about was not actually glass. Aside from the brute 58 00:03:55,160 --> 00:03:59,120 Speaker 1: physical implausibility of this story, there's some other compelling reasons 59 00:03:59,160 --> 00:04:02,240 Speaker 1: to think it's proudly nothing more than a misinterpreted rumor 60 00:04:02,400 --> 00:04:06,040 Speaker 1: or fantasy. The earliest versions of the legend crop up 61 00:04:06,080 --> 00:04:10,640 Speaker 1: in first century CE sources like the Satiricon of Petronius, 62 00:04:10,640 --> 00:04:14,200 Speaker 1: where it appears in the explicit context of fiction. The 63 00:04:14,240 --> 00:04:18,159 Speaker 1: Satiricon is a sort of absurdest comic novel, involving lots 64 00:04:18,200 --> 00:04:23,520 Speaker 1: of crude sexual humor and vignettes about werewolves and cannibalism. 65 00:04:23,560 --> 00:04:26,760 Speaker 1: The story of flexible glass is also told by Plenty 66 00:04:26,720 --> 00:04:30,880 Speaker 1: of the Elder in his first century Encyclopedia The Natural History. 67 00:04:31,279 --> 00:04:35,200 Speaker 1: One of Isadore's sources, Plenty rights that after the invention 68 00:04:35,320 --> 00:04:39,800 Speaker 1: was revealed quote, the manufactory of the artist was totally destroyed, 69 00:04:39,920 --> 00:04:42,600 Speaker 1: we are told, in order to prevent the value of copper, 70 00:04:42,960 --> 00:04:47,279 Speaker 1: silver and gold from being depreciated. I assume the logic 71 00:04:47,320 --> 00:04:49,800 Speaker 1: complied in the story is that Tiberius would have been 72 00:04:49,839 --> 00:04:53,400 Speaker 1: concerned that if glass were just as malleable as gold 73 00:04:53,440 --> 00:04:57,240 Speaker 1: and silver, the accumulated fortunes in those medals belonging to 74 00:04:57,279 --> 00:05:00,880 Speaker 1: the rich people of Rome, including Tiberius him self would 75 00:05:00,880 --> 00:05:03,920 Speaker 1: become worthless. In other words, you could think of this 76 00:05:03,960 --> 00:05:08,240 Speaker 1: as an early form of science fiction, utopian or dystopian, 77 00:05:08,440 --> 00:05:12,360 Speaker 1: depending on your perspective about how a technological change could 78 00:05:12,400 --> 00:05:14,800 Speaker 1: have led to a revolution in the class structure of 79 00:05:14,800 --> 00:05:19,880 Speaker 1: an empire. But whatever the political implications, Plenty expresses skepticism 80 00:05:19,920 --> 00:05:23,799 Speaker 1: about the story, writing that it's often repeated without much evidence. 81 00:05:24,600 --> 00:05:27,479 Speaker 1: But despite Plenty's doubts, the idea of glass that could 82 00:05:27,560 --> 00:05:31,719 Speaker 1: bend without breaking had a tenacious legacy. Malleable glass would 83 00:05:31,720 --> 00:05:34,599 Speaker 1: become one of the enduring obsessions of the alchemists of 84 00:05:34,640 --> 00:05:37,840 Speaker 1: the Middle Ages through the Renaissance in the early Modern period, 85 00:05:38,160 --> 00:05:40,880 Speaker 1: though many of them never made an explicit connection to 86 00:05:40,920 --> 00:05:44,600 Speaker 1: the story of Tiberius in the Lost Technology. In a 87 00:05:45,600 --> 00:05:50,359 Speaker 1: article for Renaissance quarterly called Storied Objects, Scientific Objects and 88 00:05:50,440 --> 00:05:55,320 Speaker 1: Renaissance Experiment the Case of malleable Glass, author Vera Keller 89 00:05:55,440 --> 00:05:58,360 Speaker 1: writes that from around the time of the thirteenth century, 90 00:05:58,760 --> 00:06:01,680 Speaker 1: the power of making alleable glass was one of the 91 00:06:01,760 --> 00:06:06,160 Speaker 1: wonders attributed to the Philosopher's Stone, while on the other hand, 92 00:06:06,440 --> 00:06:11,080 Speaker 1: straightforward recipes for softening glass appeared in several books of 93 00:06:11,160 --> 00:06:15,839 Speaker 1: secret knowledge between the thirteen and eighteen centuries. These recipes 94 00:06:15,880 --> 00:06:19,160 Speaker 1: often claimed that if followed, glass could be made soft 95 00:06:19,320 --> 00:06:24,200 Speaker 1: like leather, cloth, or even dough. Many of the recipes 96 00:06:24,240 --> 00:06:26,919 Speaker 1: call for the blood of a goat, while one mentioned 97 00:06:26,960 --> 00:06:29,839 Speaker 1: in a footnote by Keller calls for immersing glass in 98 00:06:29,880 --> 00:06:33,919 Speaker 1: the oil of horse hoofs. Despite the great effort poured 99 00:06:33,960 --> 00:06:37,640 Speaker 1: into discovering the lost secret of malleable glass, it always 100 00:06:37,640 --> 00:06:41,800 Speaker 1: eluded us. However, today it looks like we may becoming 101 00:06:41,920 --> 00:06:46,120 Speaker 1: full circle on the promise of vitrum flexila. Of course, 102 00:06:46,160 --> 00:06:49,120 Speaker 1: since the plastics revolution of the twentieth century, we've had 103 00:06:49,200 --> 00:06:52,799 Speaker 1: lots of polymer based consumer materials that are both flexible 104 00:06:52,920 --> 00:06:56,280 Speaker 1: and transparent, though that material may not always have the 105 00:06:56,320 --> 00:06:59,680 Speaker 1: exact properties of silicate glass. And even when you're talking 106 00:06:59,720 --> 00:07:03,719 Speaker 1: about genuine glass, there are researchers working hard to make 107 00:07:03,760 --> 00:07:07,480 Speaker 1: it bend without breaking, often in the context of designing 108 00:07:07,600 --> 00:07:11,440 Speaker 1: screens for current and upcoming models of phones that can 109 00:07:11,480 --> 00:07:15,760 Speaker 1: fold like a wallet without cracking their screens. These innovations 110 00:07:15,800 --> 00:07:19,480 Speaker 1: in foldable glass are explored in a February article for 111 00:07:19,520 --> 00:07:22,400 Speaker 1: The Verge by Sean Hollister, who quotes m I T 112 00:07:22,560 --> 00:07:26,720 Speaker 1: Associate Professor of material Science J. J. Who and explaining 113 00:07:26,760 --> 00:07:29,640 Speaker 1: that there are two main tricks to making glass that 114 00:07:29,720 --> 00:07:33,480 Speaker 1: can bend like plastic. One of those tricks takes us 115 00:07:33,480 --> 00:07:37,040 Speaker 1: back to what I mentioned already about microscopic flaws and 116 00:07:37,120 --> 00:07:40,240 Speaker 1: defects in the structure of the glass that allow cracks 117 00:07:40,280 --> 00:07:44,400 Speaker 1: to propagate. Researchers are trying to prevent the formation of 118 00:07:44,440 --> 00:07:47,880 Speaker 1: these tiny flaws through the use of special chemical baths 119 00:07:47,880 --> 00:07:51,800 Speaker 1: and heat treatment during the manufacturing process. But the second 120 00:07:51,800 --> 00:07:55,720 Speaker 1: trick is thinness. While glass the thickness of a window 121 00:07:55,760 --> 00:07:59,640 Speaker 1: pane will probably always shatter before it bends, glass less 122 00:07:59,640 --> 00:08:02,000 Speaker 1: than a under in microns thick which is about the 123 00:08:02,000 --> 00:08:05,120 Speaker 1: width of a human hair, can fold a surprising amount, 124 00:08:05,480 --> 00:08:08,040 Speaker 1: and once the thickness is down to a few tens 125 00:08:08,080 --> 00:08:11,760 Speaker 1: of microns, researchers claim that the glass can fold almost 126 00:08:11,840 --> 00:08:15,559 Speaker 1: flat upon itself without breaking and without a large hinge gap, 127 00:08:15,880 --> 00:08:19,160 Speaker 1: which is what the manufacturers of these phones ultimately want. 128 00:08:19,840 --> 00:08:22,160 Speaker 1: And one of my favorite details is that some of 129 00:08:22,200 --> 00:08:26,680 Speaker 1: the new flexible glass could be created with alternative chemical compositions, 130 00:08:26,960 --> 00:08:29,800 Speaker 1: by making the glass not out of silica, but out 131 00:08:29,800 --> 00:08:33,880 Speaker 1: of materials like aluminum oxide, which in its condensed crystalline 132 00:08:33,920 --> 00:08:45,080 Speaker 1: form is what makes a Sapphire. Tune into new editions 133 00:08:45,080 --> 00:08:48,800 Speaker 1: of the Artifact every Wednesday, hosted by either Robert or myself. 134 00:08:49,320 --> 00:08:52,560 Speaker 1: As always, you can email us at contact at stuff 135 00:08:52,600 --> 00:09:03,200 Speaker 1: to Blow your Mind dot com. Stuff to Blow Your 136 00:09:03,200 --> 00:09:06,319 Speaker 1: Mind is production of iHeartRadio. For more podcasts from my 137 00:09:06,360 --> 00:09:09,400 Speaker 1: Heart Radio, visit the iHeart Radio app, Apple Podcasts, or 138 00:09:09,440 --> 00:09:11,160 Speaker 1: wherever you listen to your favorite shows.