Q: Remember the erasable pen? It's easy to see how it's different from a regular pen, but why not just use a pencil instead?
A: The erasable pen, incredibly popular when introduced back in the early 1980s, has never gone away. Some of the biggest office supply companies are still making and marketing them. But why pick up a pack of pens when you can get a pencil for a fraction of the cost?
Erasable pens were popular because they combined the readibility and professional appearance of black or blue ink -- that sense of permanence! -- with the best feature of a pencil. But they largely fell out of favor after only a few years because, just like the pencil, they smudged when rubbed or when papers were shuffled together.
If you can manage to keep your hands off the ink for about a day, though, your chicken scratches will set and you will be left with error-free pages that look as though they were drafted with only the confidence that a pen can provide.
It's not actually ink at all, though. While traditional pens use inks made from oils and dyes that stain paper, erasable pens use a liquid rubber cement solution that is layered on top of the paper. Indistinguishable in appearance from regular ink, erasable "ink" can only be erased cleanly for about 10 hours. After that, the rubber cement hardens.
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