1 00:00:01,920 --> 00:00:07,040 Speaker 1: Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff, 2 00:00:07,080 --> 00:00:10,799 Speaker 1: Lauren bog Obam. Here. If you're a human who grows 3 00:00:10,880 --> 00:00:14,600 Speaker 1: hair and occasionally attempts to remove some of it, there's 4 00:00:14,640 --> 00:00:17,599 Speaker 1: a decent chance that you've stood over the bathroom sink 5 00:00:17,720 --> 00:00:20,799 Speaker 1: or in the shower and wondered, how is it possible 6 00:00:20,880 --> 00:00:24,919 Speaker 1: that your hair can dull a razor blade. Hair is 7 00:00:25,040 --> 00:00:28,360 Speaker 1: notoriously strong for its thickness, but come on, it's a 8 00:00:28,520 --> 00:00:31,800 Speaker 1: stainless steel razor blade. That's gotta be stronger than a 9 00:00:31,840 --> 00:00:35,640 Speaker 1: little old strand of hair, right. It turns out scientists 10 00:00:35,640 --> 00:00:38,800 Speaker 1: have wondered the same thing, and now we've got an answer, 11 00:00:39,120 --> 00:00:42,120 Speaker 1: and that answer is heterogeneity, of which is when an 12 00:00:42,120 --> 00:00:48,400 Speaker 1: object's composition isn't completely uniform. But let's back up. So 13 00:00:48,760 --> 00:00:52,600 Speaker 1: hair is indeed softer than steel. You might have noticed 14 00:00:52,680 --> 00:00:56,480 Speaker 1: this yourself. It's about fifty times softer than the stainless 15 00:00:56,520 --> 00:01:00,120 Speaker 1: steel used in razor blades, and yet the race or 16 00:01:00,120 --> 00:01:03,480 Speaker 1: blades we used for shaving get dull fairly quickly. A 17 00:01:03,560 --> 00:01:05,560 Speaker 1: team of scientists at m I t S Department of 18 00:01:05,600 --> 00:01:08,880 Speaker 1: Material Signs and Engineering wanted to find out why, and 19 00:01:08,920 --> 00:01:12,400 Speaker 1: their results were published in August and the journal Science. 20 00:01:13,480 --> 00:01:16,680 Speaker 1: Researcher Jean Luca Or Sholey started by shaving his own 21 00:01:16,680 --> 00:01:20,199 Speaker 1: facial hair with disposable razors and taking those blades into 22 00:01:20,200 --> 00:01:23,640 Speaker 1: the lab to be examined with a scanning electron microscope. 23 00:01:24,040 --> 00:01:26,319 Speaker 1: He found that the edges of the metal weren't rounding 24 00:01:26,440 --> 00:01:29,640 Speaker 1: or being worn down as you might expect. Rather, they 25 00:01:29,640 --> 00:01:33,559 Speaker 1: were chipping and cracking. So he created a mechanized shaving 26 00:01:33,560 --> 00:01:37,200 Speaker 1: apparatus in the lab for a more controlled testing, and 27 00:01:37,319 --> 00:01:40,880 Speaker 1: he built it to fit inside that electron microscope. He 28 00:01:41,000 --> 00:01:43,319 Speaker 1: used hair from himself and his lab mats, and blades 29 00:01:43,360 --> 00:01:47,600 Speaker 1: from commercially available razors. What were Sholey and his co 30 00:01:47,680 --> 00:01:50,360 Speaker 1: authors on the study found was that chips were more 31 00:01:50,400 --> 00:01:53,080 Speaker 1: likely to occur in the blade's edge when the hair 32 00:01:53,280 --> 00:01:55,840 Speaker 1: was able to bend before being cut by the blade. 33 00:01:56,480 --> 00:02:00,080 Speaker 1: So the team went even further to create computer simulations 34 00:02:00,120 --> 00:02:04,560 Speaker 1: with more variations different hair, different cutting angles, different directions 35 00:02:04,600 --> 00:02:08,359 Speaker 1: of force being applied, and different materials used in the blade. 36 00:02:09,600 --> 00:02:12,799 Speaker 1: They found that the chips appeared under three conditions, when 37 00:02:12,840 --> 00:02:15,200 Speaker 1: the blade approached to the hair at an angle, when 38 00:02:15,240 --> 00:02:18,840 Speaker 1: the blade was heterogeneous in composition, and when the hair 39 00:02:18,960 --> 00:02:22,919 Speaker 1: met the blade at a week point. Heterogeneous means that 40 00:02:22,960 --> 00:02:26,880 Speaker 1: the blades material is not perfectly uniform. Thus, there are 41 00:02:26,919 --> 00:02:30,440 Speaker 1: microscopic imperfections in the steel that allowed chips to happen 42 00:02:30,560 --> 00:02:33,280 Speaker 1: when it comes into contact with something, even something as 43 00:02:33,320 --> 00:02:36,720 Speaker 1: relatively soft as a hair. The presence of those tiny 44 00:02:36,800 --> 00:02:39,639 Speaker 1: cracks in the material increases stress to the rest of 45 00:02:39,680 --> 00:02:42,919 Speaker 1: the material, meaning that when there's one chip, there will 46 00:02:43,000 --> 00:02:46,360 Speaker 1: be more chips breaking apart that fine edge and resulting 47 00:02:46,480 --> 00:02:50,040 Speaker 1: in a dull blade. The researchers are now working on 48 00:02:50,120 --> 00:02:54,200 Speaker 1: creating a more homogeneous or uniform steel material for sharper, 49 00:02:54,480 --> 00:03:02,600 Speaker 1: longer lasting blades. Today's episode was written by Kristen hall 50 00:03:02,639 --> 00:03:05,240 Speaker 1: Geisler and produced by Tyler Clang. For more on this 51 00:03:05,320 --> 00:03:07,600 Speaker 1: and lots of other sharp topics, visit how stuff works 52 00:03:07,600 --> 00:03:10,560 Speaker 1: dot com. Brain Stuff is production of iHeart Radio or 53 00:03:10,639 --> 00:03:13,239 Speaker 1: more podcasts. My heart Radio visit the iHeart Radio app, 54 00:03:13,280 --> 00:03:15,959 Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.