A note on the permanent setting of human hair
Max Feughelman

Synopsis

In the standard permanent setting procedure for human hair, ammonium thioglycollate is applied to the curled hair. Disulfide bonds are converted to sulfhydril groups to enable the protein structure of the hair fibers to relax mechanically by the mechanism of sulfhydril disulfide interchange. After relaxation, the sulfhydril groups are reoxidized (neutralized) to reform the disulfide bonds, thus stabilizing the curled conformation. If the mechanical relaxation is carried out at an elevated temperature, the relaxation can occur with a much lower coversion of disulfide to sulfhydril groups. If at these elevated temperatures, the density of sulfhydril groups formed is low, returning the hair fibers to room temperature is sufficient to stabilize the curl. This eliminates the need for oxidation of the sulfhydril groups back to disulfides and results in major benefits of time saved and fiber degradation as observed by appearance and feel. Other benefits are also noted for the application of this technique to the permanent waving procedure.

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