The Chemistry of Rebonding and Perming

Some of us have naturally straight hair but want it curled; others have it naturally curled but want it straight. But whatever the style you like, there is definitely chemistry involved!

Our hair is largely made up of the protein keratin, which are rich in the naturally occurring alpha amino acid, cysteine. The side chain of cysteine molecules contain thiol -SH groups, which holds keratin together via formation of disulfide (S-S) linkages.

Hair perming involves breaking of these S-S linkages with a reducing agent, e.g. ammonium thioglycolate. When broken, the keratin molecules are free to move and adjust to the shape of the desired curl. A ‘neutrailiser’ e.g. hydrogen peroxide, is then added to reform the S-S bonds and lock the curls in place.

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