How do erasers erase? You probably dont think about pencils and erasers much in todays world of digital and mobile access to everything; while its undeniable that the No. 2 pencil and the SAT have a long history together, pencils dont really come up much outside of standardized testing anymore. But despite our devotion to our devices, Americans still use more than 2 billion pencils every year . Contrary to popular belief, pencils arent really made with lead, and havent been since Roman scribes wrote on papyrus -- thats a common pencil myth. So if you chew on your pencils, rest assured you wont become ill from lead poisoning (although thats not a free pass to snack on a No. 2). Todays pencils are made with graphite, water and clay (which is used as a binder), and pencil lead has been made this way since Nicolas-Jacques Conté invented the mixture in 1795 [source: Ritter]. They werent topped with an eraser tip, though, until about a century later. And its this companion to the pencil, the eraser, that were interested in here. Erasers eradicate pencil markings by lifting graphite from the paper youve written on. As you write, particles of graphite from your pencil mingle with and cling to particles in the fiber of the paper. Heres the science: Modern erasers are almost always made from petroleum-based synthetic rubber compounds, typically polyvinyl chloride (theyre no longer made from natural latex rubber, which is an allergen for some people). Because the particles in the polymer that make up an eraser are stickier than paper, those graphite particles get stuck to the eraser instead. Some erasers are stickier than others and absorb graphite particles more easily, giving you a cleaner, less-abrasive result.
Posted on: Wed, 28 May 2014 11:13:07 +0000
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