Chemical Waving and Straightening
How the chemistry works
Chemical waving and straightening break and rebuild disulfide bonds in the hair. The reducing agent (usually ammonium thioglycolate in waves, or a straightening product) breaks the bonds; the neutraliser or oxidiser rebuilds them in the new shape. Because the process changes the hair's internal structure, hair condition, porosity and previous chemical history determine whether it is safe to proceed.
The process
- Consult and strand test.
- Shampoo and prepare the hair; do not scalp-massage vigorously before a wave.
- Section and wind rods with even tension; use end papers to protect ends.
- Apply lotion, process and check development with a test curl.
- Rinse thoroughly, blot, then apply neutraliser and process.
- Remove rods carefully, rinse and condition.
Straightening
Relaxers and straightening systems require careful timing and thorough rinsing. Thermal straightening with irons requires heat protection and controlled temperature. Never straighten over hair that is already chemically damaged without assessment.
Traps in questions
Questions often test the difference between the reducing and oxidising stages, or ask what a test curl shows (development, not final style). Do not process against manufacturer timings, and do not skip neutralising; incomplete neutralisation leaves bonds broken and hair weak. Remember that a wave cannot be undone by another wave.
Rule of thumb
Break, shape, rebuild. If any stage is rushed, the result is frizz, weakness or breakage.