Final answer:
The processing during a permanent wave is determined by the strength of the permanent waving solution, mainly ammonium thioglycolate, which alters the disulfide bonds in hair strands.
Step-by-step explanation:
The amount of processing during a permanent wave is determined by the strength of the permanent waving solution. In the permanent waving process, a reducing substance, usually ammonium thioglycolate, is applied to the hair. This chemical reduces and ruptures some of the hair's disulfide bonds, allowing the hair to take on a new shape when wrapped around forms to produce curls or waves. The processing time and eventual results depend on the solution's concentration, which in turn dictates how extensively the disulfide bonds within the hair are disrupted and reformed.
Unlike permanent waves, temporary waves involve the disruption of hydrogen bonds within the hair through the addition of water molecules. These bonds are weaker than disulfide bonds, so when the hair dries and new hydrogen bonds form, the hair can maintain the new shape for a short period until it gets wet again.