Chemical Texture Services (Permanent Waving and Relaxing)
Chemistry of curl and straight
Permanent waving and relaxing both break and rebuild disulfide bonds in the cortex. Thioglycolate (alkaline) and acid waves use reducing agents to break bonds; the neutralizer (hydrogen peroxide or sodium bromate) rebuilds them in the new shape. Relaxers use sodium hydroxide (lye, high pH) or guanidine/ammonium (no-lye) to straighten by breaking bonds; a neutralizer or acid rinse stops the action. Trap: forgetting the neutralizer is what sets the shape - without it, the wave or relaxer continues processing.
Wrapping and processing
Wrapping determines the curl pattern: bookend/straight wrap (uniform), spiral (vertical), croquinole/piggyback (for long hair), weave (alternating). Rod size and processing time control tightness; larger rods and shorter time give looser curl. Test curl before neutralizing.
Relaxer safety
Base the scalp and hairline to protect skin. Apply relaxer quickly and evenly, avoiding overlapping on previously relaxed hair (risk of breakage). Do not relax over a fresh color service or on irritated scalp. Relaxer retouch applies product to new growth only. Recognize chemical burn and overprocessing (limp, gummy hair) and stop immediately.
Worked rule of thumb
"Break, shape, rebuild." Every texture service is break bonds, form the shape, then neutralize to lock it in.