Chemical Texturizing and Relaxing
Chemistry
Relaxers break the disulfide bonds in the cortex. Sodium hydroxide (lye) relaxers are strong and fast; no-lye relaxers use guanidine or calcium hydroxide and are gentler on the scalp but can leave mineral buildup. Thio relaxers (ammonium thioglycolate) work at a lower pH for soft curl and wave services and require a neutralizer to rebuild bonds. Curling perms use thioglycolate to reshape hair around a rod.
The relaxer service
Shampoo and dry the hair without conditioner on the scalp, protect with base cream, apply in the correct order - usually scalp first for a retouch, ends last - process without scratching, rinse thoroughly, then neutralize with shampoo until the indicator shows neutral, apply a normalizing or acid-balancing solution, and condition. A patch test and strand test come before the service.
Worked example
A client is eight weeks past her last relaxer. Apply relaxer to the new growth only, not pulling it through the previously relaxed hair, because re-relaxing processed length causes overlapping and breakage. In the last few minutes, smooth through the mid-shaft for blending.
Safety
Never relax hair with an irritated or broken scalp. Never substitute a relaxer for a touch-up on bleached hair without a strand test. Always neutralize - residual relaxer keeps breaking bonds.
Traps
Skipping neutralization. Relaxing over a scratched scalp. Mixing no-lye relaxer in a metal bowl. Assuming "no-base" means no protection at all. Timing from the end of application rather than from the start.