Chemical Texture Services (Permanent Waving and Relaxing)
The chemistry
Both perming and relaxing work on disulfide bonds in the cortex. A reducing agent breaks those bonds; an oxidizing agent (neutralizer) rebuilds them in the new shape.
Permanent waves use ammonium thioglycolate (alkaline) or bisulfite (acid-balanced, gentler, no heat). Relaxers are either hydroxide (sodium hydroxide - "lye"; guanidine or lithium hydroxide - "no-lye") or thio (ammonium thioglycolate). Hydroxide relaxers are strongly alkaline (roughly pH 12–14) and are not compatible with acid-balanced neutralizers; thio relaxers (roughly pH 9–10) are neutralized with an oxidizing neutralizer.
Application rules
- Always perform a patch test and a strand test.
- Do not relax hair that has been treated with metallic salts or compound henna.
- Apply protective base cream and shield the scalp; product goes on the new growth only during a retouch.
- Never shampoo, scratch, or strongly manipulate the scalp right before a relaxer.
- Rinse thoroughly, then use the neutralizing shampoo to stop the chemical action and restore pH.
- Check elasticity and porosity before processing; poor elasticity means do not proceed.
Traps to expect
Questions may call a neutralizer an acid (it is an oxidizer) or claim hydroxide relaxers can be neutralized with thioglycolate neutralizer. Another trap: assuming no-lye relaxers are gentler on the hair shaft - they are less irritating to scalp but can be more drying.
Worked example
A client returns for a relaxer retouch six weeks after the last service. Rule of thumb: new growth only, last few minutes for smoothing. Pulling relaxer through previously relaxed hair risks overlap and breakage.