Ask A Scientist© Biology Archive

name         Willa
status       student
age          16

Question -   How do hair permanents work? I read that an alkaline
solution breaks the chemical bonds that hold the hair's protein molecules
together. Can you give me any more information?
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Hair contains thiol (-SH) groups.  These help to stabilize the structure of
your hair by oxidatively cross-linking to form disulfides (-SS-).  Overall,
the chemical reaction is

        2 -SH + 1/2 O2 --> -S-S- + H2O.

Perms work by breaking the disulfide bonds and then forming new ones with
the hair in the position you want it.  The new disulfide bonds keep the
hair curling the way it was set.


                Richard Barrans Jr., Ph.D.
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