Final answer:
The strength of a permanent wave is based on the concentration of ammonium thioglycolate, the reducing agent that alters disulfide bonds in hair.
Step-by-step explanation:
The strength of any permanent wave is based on the concentration of its reducing agent, typically ammonium thioglycolate. In the permanent wave process, this chemical is responsible for breaking and reforming the disulfide bonds that give hair its structure. When the solution is applied, the disulfide bonds are reduced, which allows the hair to be shaped. Once the hair is set to the desired curl or wave, an oxidizing agent is used to reform the disulfide bonds, securing the new shape.
Temporary waves, on the other hand, involve the disruption of hydrogen bonds in the hair through the application of water. These bonds are weaker than disulfide bonds and re-form as the hair dries, which can help to maintain a new shape for a short period of time.