Final answer:
Coarse or resistant hair types require a more alkaline solution for permanent waving to effectively break and reform disulfide bonds, shaping the hair into curls or waves.
Step-by-step explanation:
The type of hair that will need a more alkaline solution to achieve permanent waving is hair that is less porous, such as coarse or resistant hair. Permanent waving involves breaking and reforming the disulfide bonds in hair through chemical reactions. In the process of permanent waving, an alkaline solution is used to swell the hair and open the cuticle layer, allowing a reducing agent, usually ammonium thioglycolate, to penetrate the cortex and break disulfide bonds. After the hair is set on rollers to achieve the desired shape, an oxidizing agent, like hydrogen peroxide, is used to neutralize the reaction and reform new disulfide bonds, locking the hair in the new shape.
In order to achieve permanent waving, a basic reducing substance is added to the hair to reduce and rupture some of the disulfide cross-links (Figure 21.6.13). This basic reducing substance is usually ammonium thioglycolate, which acts as an alkaline solution.
The type of hair that will need a more alkaline solution to achieve permanent waving is hair that has stronger, more tightly cross-linked disulfide bonds. This is usually the case with coarse or resistant hair.
On the other hand, hair that has weaker disulfide bonds, such as fine or weak hair, will require a less alkaline solution for permanent waving.