Final answer:
A hair strand test is used to determine how hair will react to a permanent wave by applying the perming solution to a small section of hair. Ammonium thioglycolate is used to break disulfide bonds in hair strands during permanent waving, after which the hair is reshaped and the disulfide bonds are reformed to create the permanent wave.
Step-by-step explanation:
To determine how a client's hair will react to the permanent waving process, professionals typically conduct a hair strand test. This test involves applying the perming solution to a small section of the client's hair to observe the reaction and ensure it can handle the chemicals without damage. The reaction of hair is influenced by its porosity, texture, and previous chemical treatments.
During a permanent wave, a reducing agent, commonly ammonium thioglycolate, is applied to the hair, which breaks down the disulfide bonds responsible for hair's strength and shape. Once these bonds are broken, the hair can be reshaped around curling rods, and a neutralizer is applied to reform the bonds in their new shape, resulting in a permanent wave.
The steps for forming temporary waves involve wetting the hair, breaking hydrogen bonds as the hair is set into the desired shape, and reforming those bonds as the hair dries. This process is not as long-lasting as a permanent wave since it does not involve breaking and reforming disulfide bonds.