WEBVTT - How Can Hair Be Tougher than Razor Blades?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,

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<v Speaker 1>Lauren bog Obam. Here. If you're a human who grows

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<v Speaker 1>hair and occasionally attempts to remove some of it, there's

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<v Speaker 1>a decent chance that you've stood over the bathroom sink

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<v Speaker 1>or in the shower and wondered, how is it possible

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<v Speaker 1>that your hair can dull a razor blade. Hair is

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<v Speaker 1>notoriously strong for its thickness, but come on, it's a

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<v Speaker 1>stainless steel razor blade. That's gotta be stronger than a

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<v Speaker 1>little old strand of hair, right. It turns out scientists

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<v Speaker 1>have wondered the same thing, and now we've got an answer,

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<v Speaker 1>and that answer is heterogeneity, of which is when an

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<v Speaker 1>object's composition isn't completely uniform. But let's back up. So

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<v Speaker 1>hair is indeed softer than steel. You might have noticed

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<v Speaker 1>this yourself. It's about fifty times softer than the stainless

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<v Speaker 1>steel used in razor blades, and yet the race or

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<v Speaker 1>blades we used for shaving get dull fairly quickly. A

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<v Speaker 1>team of scientists at m I t S Department of

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<v Speaker 1>Material Signs and Engineering wanted to find out why, and

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<v Speaker 1>their results were published in August and the journal Science.

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<v Speaker 1>Researcher Jean Luca Or Sholey started by shaving his own

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<v Speaker 1>facial hair with disposable razors and taking those blades into

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<v Speaker 1>the lab to be examined with a scanning electron microscope.

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<v Speaker 1>He found that the edges of the metal weren't rounding

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<v Speaker 1>or being worn down as you might expect. Rather, they

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<v Speaker 1>were chipping and cracking. So he created a mechanized shaving

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<v Speaker 1>apparatus in the lab for a more controlled testing, and

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<v Speaker 1>he built it to fit inside that electron microscope. He

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<v Speaker 1>used hair from himself and his lab mats, and blades

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<v Speaker 1>from commercially available razors. What were Sholey and his co

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<v Speaker 1>authors on the study found was that chips were more

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<v Speaker 1>likely to occur in the blade's edge when the hair

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<v Speaker 1>was able to bend before being cut by the blade.

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<v Speaker 1>So the team went even further to create computer simulations

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<v Speaker 1>with more variations different hair, different cutting angles, different directions

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<v Speaker 1>of force being applied, and different materials used in the blade.

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<v Speaker 1>They found that the chips appeared under three conditions, when

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<v Speaker 1>the blade approached to the hair at an angle, when

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<v Speaker 1>the blade was heterogeneous in composition, and when the hair

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<v Speaker 1>met the blade at a week point. Heterogeneous means that

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<v Speaker 1>the blades material is not perfectly uniform. Thus, there are

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<v Speaker 1>microscopic imperfections in the steel that allowed chips to happen

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<v Speaker 1>when it comes into contact with something, even something as

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<v Speaker 1>relatively soft as a hair. The presence of those tiny

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<v Speaker 1>cracks in the material increases stress to the rest of

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<v Speaker 1>the material, meaning that when there's one chip, there will

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<v Speaker 1>be more chips breaking apart that fine edge and resulting

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<v Speaker 1>in a dull blade. The researchers are now working on

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<v Speaker 1>creating a more homogeneous or uniform steel material for sharper,

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<v Speaker 1>longer lasting blades. Today's episode was written by Kristen hall

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<v Speaker 1>Geisler and produced by Tyler Clang. For more on this

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<v Speaker 1>and lots of other sharp topics, visit how stuff works

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<v Speaker 1>dot com. Brain Stuff is production of iHeart Radio or

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