Speaker 1: Welcome to brain Stuff from How Stuff Works. Hi, brain Stuff,
Speaker 1: I'm Lauren voc Obam, and I've got something different for
Speaker 1: you today. One of our classic episodes the topic how
Speaker 1: do erasers a Race? This one was performed by our
Speaker 1: previous host, Christian Sager and written by me, except for
Speaker 1: the list in the beginning that was all Christian. I'll
Speaker 1: let him take it away, everybody. I'm Christian Sager. This
Speaker 1: is brain Stuff, and there are plenty of things I'd
Speaker 1: like to erase. Maybe the sushi that gave me food
Speaker 1: poisoning at one time, watching Battlefield Earth, and and pretty
Speaker 1: much every tweet I ever read about Hamilton's and Mike Pence. Unfortunately,
Speaker 1: a lot of marks in this world, however, are permanent.
Speaker 1: But not so with pencil marks. Yes, the humble pencil,
Speaker 1: or not so humble as the case. Maybe even in
Speaker 1: this our digital age, about fifteen to twenty billion pencils
Speaker 1: are manufactured each year. Each one holds the approximate capacity
Speaker 1: to draw a line seven hundred and thirty two miles long,
Speaker 1: or to write forty thousand words, all of which can
Speaker 1: easily be erased. This blissful impermanence is thanks to the
Speaker 1: materials that pencils and erasers are made from. See pencil
Speaker 1: lead isn't actually lead at all, So no, you can't
Speaker 1: get lead poisoning from a pencil wound. It's made from graphite,
Speaker 1: which is a soft mineral made up of flaky, atom
Speaker 1: thin layers of crystalline carbon. Ever since the seventeen nineties,
Speaker 1: that graphite has been mixed with clay to achieve different
Speaker 1: pencil lead hardness. Now, as you write or draw, flakes
Speaker 1: of this clay and graphite mix cling to the fibers
Speaker 1: that make up your piece of paper, and it is
Speaker 1: a happening party for all particles involved. The fibers have
Speaker 1: a huge surface area that catches lots of flakes, and
Speaker 1: the flakes will gladly stick around for decades if they're
Speaker 1: not disturbed. But erasers can lift those flakes right off
Speaker 1: the page by virtue of being stickier than the paper fibers.
Speaker 1: It's as simple as that. Since the flakes are just
Speaker 1: hanging onto the paper, anything stickier than paper can lift
Speaker 1: them off. In fact, the earliest erasers, going back to
Speaker 1: at least the fifteen hundreds, were just bread slightly moistened
Speaker 1: and baled up. Bread. Yeah, imagine what that tastes like
Speaker 1: with pencil shavings in it. By the eighteen hundreds, people
Speaker 1: were using erasers made from natural rubber, which is harvested
Speaker 1: in the form of latex from certain trees, which excrete
Speaker 1: it to discourage plant eating insects. The name rubber actually
Speaker 1: comes from one chemist's observation Circus seventeen seventy that this
Speaker 1: tree latex stuff is great when used to quote rub
Speaker 1: out pencil marks. But because natural latex rubber can be
Speaker 1: expensive and some people are allergic to it, modern erasers
Speaker 1: are almost always made from synthetic petroleum based rubber, like
Speaker 1: polyvinyl chloride. Your standard pink eraser has bits of pumice
Speaker 1: added to it to make it more abrasive, which is
Speaker 1: a cheap way to help dislodge flakes of graphite from
Speaker 1: paper fibers. Fancier erasers are made from super sticky, soft
Speaker 1: vinyl that absorbs the graphite and is more gentle on
Speaker 1: your paper. Meanwhile, erasable pens contain ink mixed with rubber cement.
Speaker 1: While the cement is still wet, say within ten hours
Speaker 1: of writing, it will stick to an eraser, and magic
Speaker 1: erasers work on a similar principle. Magic. No, actually, it's
Speaker 1: instead of being literally sticky, they contain rigid micro structures
Speaker 1: that trap dirt. But if you're ever without one, give
Speaker 1: your standard pink eraser a try. They're effective on way
Speaker 1: more than just pencil marks. Yeah. Today's episode was produced
Speaker 1: by Tyler Clang. As I said at the top of
Speaker 1: the show, I originally wrote this script for our YouTube
Speaker 1: video series for Kristen Conger to perform. If you'd like
Speaker 1: to hear more from our former host, Christian, you can
Speaker 1: check out his new podcast super Context wherever you listen
Speaker 1: to podcasts, and of course, for lots more topics that
Speaker 1: are always updating, visit our home planet, how stuff Works
Speaker 1: dot com.