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