Material
A
strand of hair
To Do and Notice
1.
Wrap the strand of hair around your forefingers so that your fingers
are about an inch apart.
2.
Pull the hair slowly, but
firmly.
3.
Can you feel the hair stretching
out?
What's Going On?
Healthy head hair will stretch when you pull on it. That's because
the cortex of healthy hair is strong and elastic. The cortex inside
of a damaged hair strand is weak and brittle. It will break more
easily when you pull on it.
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Material
A strand of straight hair
To Do and Notice
1.
Hold
up a single strand of hair. Pinch the hair between the fingernail
of your thumb and the fleshy part of your forefinger.
2.
Run
your fingernail across the hair strand. Try not to break the hair
in two. If you do, get another hair and try again. Did your hair
curl? If not, try again. Be patient; you'll get the hang of it.
What's
Going On?
Okay, so this might not be the most efficient way to style your
hair. But this activity wouldn't be possible if it weren't for the
way the cuticle of a hair is structured. Your cuticle is made of
overlapping cells arranged like the tiles on a terra-cotta roof.
When you run your fingernails across a hair strand, you pull apart
the overlapping cells on one side of the cuticle more than you pull
apart the cells on the opposite side. The result: a tiny hair that
kinks, twists, and curls.
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