(classical music)
- I'm Cristen, and this is Brain Stuff.
And there are plenty of
things I'd like to erase.
The box of pizza rolls I ate yesterday,
ever watching Sex in the City part two,
and every single Willy Wonka meme.
Just make them stop.
Unfortunately, a lot of marks
in this world are permanent,
but not so with pencil marks.
Yes, the humble pencil, or not so humble,
as the case may be.
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 crystal and carbon.
Ever since the 1790s that
graphite has been mixed
with clay to achieve different
pencil lead hardnesses.
As you write or draw flakes
of this clay and graphite mix
cling to the fibers that
make up your piece of paper.
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,
not unlike thousands of
tiny clay and graphite
kittens just hangin' in there,
anything stickier than
paper can lift them off.
In fact, the earliest erasers
going back to at least
the 1500s were just bread,
slightly moistened and
balled up pieces of bread.
By the 1800s 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 observations circa 1770
that this tree latex stuff
is great when you use
to rub out pencil marks.
Get it?
Rub out? Rubber?
Huh?
But because natural latex
rubber can be expensive
and some people are allergic to it,
(coughs) condoms,
modern erasers are almost always made
from synthetic petroleum-based rubber
like polyvinyl chloride.
Your standard pink eraser
has bits of pumice added
to make it more abrasive,
which is a cheap way to help dislodge
flakes of graphite from
those paper fibers.
And magic erasers work
on a similar principle.
Magic.
No, 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.
So hey, I want to know.
What would you erase
if you had the chance?
Tell me in the comments
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And if you're just pining
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