Final answer:
A reduction reaction in permanent waving refers to the process of breaking and reforming disulfide bonds in the hair strands.
It involves adding a reducing substance to the hair to break some of the disulfide cross-links, allowing the alpha-helices in the hair to shift positions.
Step-by-step explanation:
Permanent waving is a two-step process involving a physical and a chemical change. The first part of any perm is the physical change caused by wrapping the hair on the rods. The second part involves the chemical changes caused by the perm solution and the neutralizer.
In permanent waving, a reduction reaction refers to the process of breaking and reforming disulfide bonds in the hair strands. During the permanent wave process, a reducing substance, such as ammonium thioglycolate, is added to the hair to reduce and rupture some of the disulfide cross-links.
This allows the alpha-helices in the hair to shift positions, creating new disulfide bond positions.
An oxidizing agent, usually hydrogen peroxide, is then added to reform the disulfide bonds in their new positions, resulting in a permanent curl. The new disulfide bond positions will hold until new hair growth occurs.