Final answer:
Most of the processing in permanent waving occurs when a reducing agent, typically ammonium thioglycolate, is applied, disrupting disulfide bonds in the hair's keratin structure. This allows the hair to be reshaped into curls or straightened. A neutralizer is then used to re-form the disulfide bonds, creating a new permanent shape.
Step-by-step explanation:
In the permanent waving process, most of the processing takes place as soon as the solution, which usually contains a basic reducing substance like ammonium thioglycolate, is applied to the hair. This chemical reduces and ruptures some of the disulfide cross-links within the keratin structure of the hair. These disulfide bonds are responsible for the hair's strength and elasticity. By breaking these bonds, the hair can be reshaped around forms to create a new lasting style, whether it is curling for perms or straightening.
The processing of the hair through the use of chemicals leads to a temporary breakage of the bonds. Once the hair is set in its new shape and the solution is rinsed out, a neutralizer is applied to re-form these disulfide bonds, hence creating a new permanent shape. The key difference between temporary and permanent waving lies in the chemical alteration of these bonds. Temporary waves, as the name suggests, only cause a transient alteration and are typically formed by simply breaking the hydrogen bonds when wetting and drying the hair.