1 00:00:02,040 --> 00:00:07,120 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hi, brain Stuff, 2 00:00:07,160 --> 00:00:09,440 Speaker 1: I'm Lauren voc Obam, and I've got something different for 3 00:00:09,480 --> 00:00:13,080 Speaker 1: you today. One of our classic episodes the topic how 4 00:00:13,119 --> 00:00:16,320 Speaker 1: do erasers a Race? This one was performed by our 5 00:00:16,360 --> 00:00:20,119 Speaker 1: previous host, Christian Sager and written by me, except for 6 00:00:20,160 --> 00:00:22,760 Speaker 1: the list in the beginning that was all Christian. I'll 7 00:00:22,800 --> 00:00:30,040 Speaker 1: let him take it away, everybody. I'm Christian Sager. This 8 00:00:30,160 --> 00:00:33,320 Speaker 1: is brain Stuff, and there are plenty of things I'd 9 00:00:33,400 --> 00:00:36,200 Speaker 1: like to erase. Maybe the sushi that gave me food 10 00:00:36,200 --> 00:00:40,320 Speaker 1: poisoning at one time, watching Battlefield Earth, and and pretty 11 00:00:40,400 --> 00:00:44,680 Speaker 1: much every tweet I ever read about Hamilton's and Mike Pence. Unfortunately, 12 00:00:45,200 --> 00:00:48,040 Speaker 1: a lot of marks in this world, however, are permanent. 13 00:00:48,520 --> 00:00:52,640 Speaker 1: But not so with pencil marks. Yes, the humble pencil, 14 00:00:52,880 --> 00:00:56,120 Speaker 1: or not so humble as the case. Maybe even in 15 00:00:56,160 --> 00:01:01,320 Speaker 1: this our digital age, about fifteen to twenty billion pencils 16 00:01:01,320 --> 00:01:05,600 Speaker 1: are manufactured each year. Each one holds the approximate capacity 17 00:01:05,680 --> 00:01:09,720 Speaker 1: to draw a line seven hundred and thirty two miles long, 18 00:01:10,080 --> 00:01:14,160 Speaker 1: or to write forty thousand words, all of which can 19 00:01:14,200 --> 00:01:19,000 Speaker 1: easily be erased. This blissful impermanence is thanks to the 20 00:01:19,040 --> 00:01:22,800 Speaker 1: materials that pencils and erasers are made from. See pencil 21 00:01:22,840 --> 00:01:26,240 Speaker 1: lead isn't actually lead at all, So no, you can't 22 00:01:26,240 --> 00:01:29,679 Speaker 1: get lead poisoning from a pencil wound. It's made from graphite, 23 00:01:29,680 --> 00:01:32,960 Speaker 1: which is a soft mineral made up of flaky, atom 24 00:01:33,080 --> 00:01:38,119 Speaker 1: thin layers of crystalline carbon. Ever since the seventeen nineties, 25 00:01:38,160 --> 00:01:41,640 Speaker 1: that graphite has been mixed with clay to achieve different 26 00:01:41,680 --> 00:01:46,080 Speaker 1: pencil lead hardness. Now, as you write or draw, flakes 27 00:01:46,120 --> 00:01:49,240 Speaker 1: of this clay and graphite mix cling to the fibers 28 00:01:49,280 --> 00:01:51,760 Speaker 1: that make up your piece of paper, and it is 29 00:01:51,840 --> 00:01:56,480 Speaker 1: a happening party for all particles involved. The fibers have 30 00:01:56,560 --> 00:01:59,360 Speaker 1: a huge surface area that catches lots of flakes, and 31 00:01:59,440 --> 00:02:03,040 Speaker 1: the flakes will gladly stick around for decades if they're 32 00:02:03,040 --> 00:02:06,960 Speaker 1: not disturbed. But erasers can lift those flakes right off 33 00:02:06,960 --> 00:02:10,800 Speaker 1: the page by virtue of being stickier than the paper fibers. 34 00:02:11,080 --> 00:02:13,440 Speaker 1: It's as simple as that. Since the flakes are just 35 00:02:13,760 --> 00:02:17,960 Speaker 1: hanging onto the paper, anything stickier than paper can lift 36 00:02:18,000 --> 00:02:21,000 Speaker 1: them off. In fact, the earliest erasers, going back to 37 00:02:21,120 --> 00:02:25,280 Speaker 1: at least the fifteen hundreds, were just bread slightly moistened 38 00:02:25,320 --> 00:02:29,000 Speaker 1: and baled up. Bread. Yeah, imagine what that tastes like 39 00:02:29,080 --> 00:02:32,840 Speaker 1: with pencil shavings in it. By the eighteen hundreds, people 40 00:02:32,880 --> 00:02:36,880 Speaker 1: were using erasers made from natural rubber, which is harvested 41 00:02:36,880 --> 00:02:40,160 Speaker 1: in the form of latex from certain trees, which excrete 42 00:02:40,160 --> 00:02:44,720 Speaker 1: it to discourage plant eating insects. The name rubber actually 43 00:02:44,840 --> 00:02:49,560 Speaker 1: comes from one chemist's observation Circus seventeen seventy that this 44 00:02:49,680 --> 00:02:53,840 Speaker 1: tree latex stuff is great when used to quote rub 45 00:02:53,840 --> 00:02:57,960 Speaker 1: out pencil marks. But because natural latex rubber can be 46 00:02:58,000 --> 00:03:02,239 Speaker 1: expensive and some people are allergic to it, modern erasers 47 00:03:02,240 --> 00:03:06,480 Speaker 1: are almost always made from synthetic petroleum based rubber, like 48 00:03:06,639 --> 00:03:11,840 Speaker 1: polyvinyl chloride. Your standard pink eraser has bits of pumice 49 00:03:11,880 --> 00:03:14,320 Speaker 1: added to it to make it more abrasive, which is 50 00:03:14,360 --> 00:03:18,280 Speaker 1: a cheap way to help dislodge flakes of graphite from 51 00:03:18,320 --> 00:03:24,200 Speaker 1: paper fibers. Fancier erasers are made from super sticky, soft 52 00:03:24,680 --> 00:03:28,280 Speaker 1: vinyl that absorbs the graphite and is more gentle on 53 00:03:28,320 --> 00:03:33,360 Speaker 1: your paper. Meanwhile, erasable pens contain ink mixed with rubber cement. 54 00:03:33,680 --> 00:03:36,920 Speaker 1: While the cement is still wet, say within ten hours 55 00:03:37,000 --> 00:03:40,680 Speaker 1: of writing, it will stick to an eraser, and magic 56 00:03:40,720 --> 00:03:45,440 Speaker 1: erasers work on a similar principle. Magic. No, actually, it's 57 00:03:45,480 --> 00:03:49,600 Speaker 1: instead of being literally sticky, they contain rigid micro structures 58 00:03:49,640 --> 00:03:52,880 Speaker 1: that trap dirt. But if you're ever without one, give 59 00:03:52,960 --> 00:03:56,760 Speaker 1: your standard pink eraser a try. They're effective on way 60 00:03:56,800 --> 00:04:05,560 Speaker 1: more than just pencil marks. Yeah. Today's episode was produced 61 00:04:05,560 --> 00:04:07,680 Speaker 1: by Tyler Clang. As I said at the top of 62 00:04:07,680 --> 00:04:10,520 Speaker 1: the show, I originally wrote this script for our YouTube 63 00:04:10,600 --> 00:04:13,680 Speaker 1: video series for Kristen Conger to perform. If you'd like 64 00:04:13,760 --> 00:04:15,880 Speaker 1: to hear more from our former host, Christian, you can 65 00:04:15,960 --> 00:04:18,960 Speaker 1: check out his new podcast super Context wherever you listen 66 00:04:19,000 --> 00:04:22,000 Speaker 1: to podcasts, and of course, for lots more topics that 67 00:04:22,040 --> 00:04:25,200 Speaker 1: are always updating, visit our home planet, how stuff Works 68 00:04:25,320 --> 00:04:37,240 Speaker 1: dot com.