Chemical Services
Chemical questions test pH, product categories, developer math, test procedures, and the safety rules that prevent injury and lawsuits.
The chemistry frame
Hair sits near pH 4.5–5.5.Temporary color coats the cuticle; semi-permanent deposits without lifting; demi-permanent deposits with low or no ammonia; permanent color lifts and deposits using aniline derivatives and requires a patch test 24–48 hours before service and a strand test for timing.
Developer volumes
10 volume deposits only; 20 volume lifts about 1–2 levels; 30 volume about 2–3; 40 volume about 3–4. Developer is never mixed with another volume to "make" a strength - the result is unpredictable.
Relaxers and perms
Sodium hydroxide (lye, very high pH), guanidine (no-lye), and ammonium thioglycolate relaxers. Perms reduce disulfide bonds with thioglycolate, then a neutralizer (hydrogen peroxide or sodium bromate) rebuilds them. Never relax or perm over broken skin, and never overlap relaxer onto previously relaxed hair.
Worked example
A client has four inches of new growth above previously relaxed ends and wants straight hair. Section and apply relaxer to the new growth only, process by strand test, rinse thoroughly, then neutralize. Carrying product onto the already-relaxed ends risks overlapping and breakage.
Traps that cost marks
Skipping the patch test, mixing brands, using metal bowls with bleach, relaxing a scalp with abrasions, and forgetting that a strand test governs timing better than the clock.