What are the two main phases of a traditional perm process?

• A. Hydrogen bonding changes due to water exposure and final neutralization.
• B. Oxidation of disulfide bonds and formation of new keratin crosslinks through heat.
• C. Line of wave formation and final shaping by hair structure.
• D. Reduction of disulfide bonds by the reducing agent and reformation of bonds under neutralization to create the curl pattern.

Answer: (D)

Hair curl from a traditional perm comes from breaking and then re-forming disulfide bonds in the hair. The two main phases are: first, a reducing agent breaks the disulfide bonds, making the hair flexible enough to be wrapped around perm rods. After rinsing, a neutralizer is applied, and its oxidizing action re-forms those bonds in the new curved configuration, locking in the curl pattern. This sequence—breaking the bonds to rearrange them, then rebuilding them in the new shape—is what creates the perm. The other descriptions mix in different chemical changes or factors (like water-related changes or heat) that aren’t the defining two-phase process.