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Speaker 1: Welcome to brain stuff. From how stuff works, everybody, I'm

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Speaker 1: Christian Seger. This is brain stuff, and there are plenty

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Speaker 1: of things I'd like to erase, maybe the sushi that

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Speaker 1: gave me food poisoning at one time, watching Battlefield Earth,

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Speaker 1: and and pretty much every tweet I ever read about

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Speaker 1: Hamilton's and Mike Pence. Unfortunately, a lot of marks in

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Speaker 1: this world, however, are permanent. But not so with pencil marks. Yes,

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Speaker 1: the humble pencil, or not so humble as the case

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Speaker 1: maybe even in this are digital age. About fifteen to

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Speaker 1: twenty billion pencils are manufactured each year. Each one holds

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Speaker 1: the approximate capacity to draw a line seven hundred and

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Speaker 1: thirty two miles long, or to write forty words, all

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Speaker 1: of which can easily be erased. This blissful impermanence is

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Speaker 1: thanks to the materials that councils and erasers are made from.

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Speaker 1: See pencil lead isn't actually lead at all, So no,

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Speaker 1: you can't get lead poisoning from a pencil wound. It's

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Speaker 1: made from graphite, which is a soft mineral made up

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Speaker 1: of flaky, atom thin layers of crystalline carbon. Ever since

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Speaker 1: the seventeen nineties that graphite has been mixed with clay

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Speaker 1: to achieve different pencil lead hardness. Now, as you write

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Speaker 1: or draw, flakes of this clay and graphite mix cling

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Speaker 1: to the fibers that make up your piece of paper,

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Speaker 1: and it is a happening party for all particles involved.

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Speaker 1: The fibers have a huge surface area that catches lots

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Speaker 1: of flakes, and the flakes will gladly stick around for

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Speaker 1: decades if they're not disturbed. But erasers can lift those

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Speaker 1: flakes right off the page by virtue of being stickier

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Speaker 1: than the paper fibers. It's as simple as that. Since

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Speaker 1: the flakes are just hanging onto the paper, anything stickier

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Speaker 1: than paper can lift them off. In fact, the earliest

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Speaker 1: array's going back to at least the fifteen hundreds were

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Speaker 1: just bread slightly moistened and baled up. Bread. Yeah, imagine

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Speaker 1: what that tastes like with pencil shavings in it. By

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Speaker 1: the eighteen hundreds, people were using erasers made from natural rubber,

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Speaker 1: which is harvested in the form of latex from certain trees,

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Speaker 1: which excrete it to discourage plant eating insects. The name

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Speaker 1: rubber actually comes from one chemist's observation Circus seventeen seventy

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Speaker 1: that this tree latex stuff is great when used to

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Speaker 1: quote rub out pencil marks, but because natural latex rubber

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Speaker 1: can be expensive and some people are allergic to it,

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Speaker 1: modern erasers are almost always made from synthetic petroleum based

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Speaker 1: rubber like polyvinyl chloride. Your standard pink eraser has bits

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Speaker 1: of pumice added to it to make it more abrasive,

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Speaker 1: which is a cheap way to help dislodge flakes of

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Speaker 1: graphite from paper fibers. Fan to your erasers are made

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Speaker 1: from super sticky soft vinyl that absorbs the graphite and

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Speaker 1: is more gentle on your paper. Meanwhile, erasable pens contain

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Speaker 1: ink mixed with rubber cement. While the cement is still wet,

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Speaker 1: say within ten hours of writing, it will stick to

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Speaker 1: an eraser. And magic erasers work on a similar principle.

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Speaker 1: Magic no, actually it's instead of being literally sticky, they

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Speaker 1: contain rigid micro structures that trap dirt. But if you're

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Speaker 1: ever without one, give your standard pink eraser a try.

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Speaker 1: They're effective on way more than just pencil marks. Check

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Speaker 1: out the brain stuff channel on YouTube and for more

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Speaker 1: on this and thousands of other topics. Visit how stuff

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Speaker 1: works dot com,