WEBVTT - BrainStuff Classics: How Do Erasers Erase?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hi, brain Stuff,

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<v Speaker 1>I'm Lauren voc Obam, and I've got something different for

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<v Speaker 1>you today. One of our classic episodes the topic how

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<v Speaker 1>do erasers a Race? This one was performed by our

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<v Speaker 1>previous host, Christian Sager and written by me, except for

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<v Speaker 1>the list in the beginning that was all Christian. I'll

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<v Speaker 1>let him take it away, everybody. I'm Christian Sager. This

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<v Speaker 1>is brain Stuff, and there are plenty of things I'd

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<v Speaker 1>like to erase. Maybe the sushi that gave me food

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<v Speaker 1>poisoning at one time, watching Battlefield Earth, and and pretty

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<v Speaker 1>much every tweet I ever read about Hamilton's and Mike Pence. Unfortunately,

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<v Speaker 1>a lot of marks in this world, however, are permanent.

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<v Speaker 1>But not so with pencil marks. Yes, the humble pencil,

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<v Speaker 1>or not so humble as the case. Maybe even in

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<v Speaker 1>this our digital age, about fifteen to twenty billion pencils

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<v Speaker 1>are manufactured each year. Each one holds the approximate capacity

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<v Speaker 1>to draw a line seven hundred and thirty two miles long,

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<v Speaker 1>or to write forty thousand words, all of which can

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<v Speaker 1>easily be erased. This blissful impermanence is thanks to the

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<v Speaker 1>materials that pencils and erasers are made from. See pencil

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<v Speaker 1>lead isn't actually lead at all, So no, you can't

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<v Speaker 1>get lead poisoning from a pencil wound. It's made from graphite,

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<v Speaker 1>which is a soft mineral made up of flaky, atom

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<v Speaker 1>thin layers of crystalline carbon. Ever since the seventeen nineties,

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<v Speaker 1>that graphite has been mixed with clay to achieve different

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<v Speaker 1>pencil lead hardness. Now, as you write or draw, flakes

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<v Speaker 1>of this clay and graphite mix cling to the fibers

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<v Speaker 1>that make up your piece of paper, and it is

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<v Speaker 1>a happening party for all particles involved. The fibers have

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<v Speaker 1>a huge surface area that catches lots of flakes, and

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<v Speaker 1>the flakes will gladly stick around for decades if they're

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<v Speaker 1>not disturbed. But erasers can lift those flakes right off

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<v Speaker 1>the page by virtue of being stickier than the paper fibers.

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<v Speaker 1>It's as simple as that. Since the flakes are just

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<v Speaker 1>hanging onto the paper, anything stickier than paper can lift

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<v Speaker 1>them off. In fact, the earliest erasers, going back to

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<v Speaker 1>at least the fifteen hundreds, were just bread slightly moistened

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<v Speaker 1>and baled up. Bread. Yeah, imagine what that tastes like

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<v Speaker 1>with pencil shavings in it. By the eighteen hundreds, people

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<v Speaker 1>were using erasers made from natural rubber, which is harvested

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<v Speaker 1>in the form of latex from certain trees, which excrete

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<v Speaker 1>it to discourage plant eating insects. The name rubber actually

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<v Speaker 1>comes from one chemist's observation Circus seventeen seventy that this

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<v Speaker 1>tree latex stuff is great when used to quote rub

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<v Speaker 1>out pencil marks. But because natural latex rubber can be

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<v Speaker 1>expensive and some people are allergic to it, modern erasers

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<v Speaker 1>are almost always made from synthetic petroleum based rubber, like

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<v Speaker 1>polyvinyl chloride. Your standard pink eraser has bits of pumice

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<v Speaker 1>added to it to make it more abrasive, which is

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<v Speaker 1>a cheap way to help dislodge flakes of graphite from

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<v Speaker 1>paper fibers. Fancier erasers are made from super sticky, soft

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<v Speaker 1>vinyl that absorbs the graphite and is more gentle on

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<v Speaker 1>your paper. Meanwhile, erasable pens contain ink mixed with rubber cement.

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<v Speaker 1>While the cement is still wet, say within ten hours

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<v Speaker 1>of writing, it will stick to an eraser, and magic

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<v Speaker 1>erasers work on a similar principle. Magic. No, actually, it's

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<v Speaker 1>instead of being literally sticky, they contain rigid micro structures

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<v Speaker 1>that trap dirt. But if you're ever without one, give

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<v Speaker 1>your standard pink eraser a try. They're effective on way

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<v Speaker 1>more than just pencil marks. Yeah. Today's episode was produced

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<v Speaker 1>by Tyler Clang. As I said at the top of

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<v Speaker 1>the show, I originally wrote this script for our YouTube

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<v Speaker 1>video series for Kristen Conger to perform. If you'd like

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<v Speaker 1>to hear more from our former host, Christian, you can

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<v Speaker 1>check out his new podcast super Context wherever you listen

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<v Speaker 1>to podcasts, and of course, for lots more topics that

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<v Speaker 1>are always updating, visit our home planet, how stuff Works

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<v Speaker 1>dot com.