Chemical Services: Permanent Waves, Relaxers, and Hair Color
This domain tests pH, bond chemistry, product selection, processing, and the timing rules that protect the hair from overlapping chemical services.
pH and bonds
Hair sits near pH 4.5 to 5.5 and skin near 5.5; water is 7. Chemical services work by breaking and rebuilding disulfide bonds under controlled pH.
Permanent waves
Alkaline waves use ammonium thioglycolate near pH 9 to 9.6; acid waves use glyceryl monothioglycolate near pH 6.5 to 7.2 and need heat to process. Wrap, apply, process, rinse thoroughly, then neutralize with hydrogen peroxide or sodium bromate to re-form the bonds before removing rods.
Relaxers
Sodium hydroxide (lye, pH 12 to 14), guanidine hydroxide (no-lye), and ammonium thioglycolate (thio) relaxers straighten by relaxing bonds. Base or no-base protects the scalp. Retouch applications go on new growth only - never pull relaxer through previously relaxed hair. Rinse completely, then use a normalizing or acid-balancing shampoo and conditioner.
Color
The level system runs 1 (black) to 10 (lightest blonde). Developer volumes: 10 (3 percent), 20 (6 percent), 30 (9 percent), 40 (12 percent). Temporary color rinses coat the cuticle; semipermanent deposits without lift; demi-permanent deposits with low-volume peroxide; permanent oxidative color lifts and deposits and requires a patch test 24 to 48 hours ahead. Lightening passes through underlying pigment stages: red, red-orange, orange, yellow-orange, yellow, pale yellow.
Worked example
A client wants a relaxer and permanent color in one visit. Break the disulfide bonds and then deposit oxidative color and the cumulative damage is unpredictable, so schedule the services at least two weeks apart and confirm with a strand test.
Traps
Skipping or under-rinsing before neutralizing; overlapping relaxer onto relaxed hair; using 40 volume on the scalp; confusing semipermanent with demi-permanent; coloring hair that carries metallic salts.