Hair Care and Hair Services
Structure before service
A hair strand has three layers: the cuticle (overlapping scales that protect the strand and must be lifted for chemicals to penetrate), the cortex (the bulk of the fiber, holding melanin, disulfide bonds, and almost all color and texture change), and the medulla (a central core that may be thin or absent, especially in fine hair). Questions frequently swap cuticle and cortex - if the stem asks where bonds break or where color is deposited, the answer is the cortex.
pH, perms, relaxers, color
The pH scale runs 0–14 with 7 neutral; hair and skin prefer the acid side (roughly 4.5–5.5). Alkaline products swell the cuticle and allow penetration; acidic products flatten it back down. Relaxers are strongly alkaline and break disulfide bonds. Perms reduce bonds with ammonium thioglycolate, then neutralize with hydrogen peroxide or sodium bromate to rebuild them. Oxidative color uses an aniline derivative, and a patch test 24–48 hours before each application is required - not just the first time.
Analysis and contraindications
Keep four analyses separate: texture (diameter of the strand), density (strands per square inch), porosity (ability to absorb and hold moisture), and elasticity (stretch and return). Growth phases are anagen (active), catagen (transition), and telogen (resting and shedding), averaging about half an inch per month. Refer rather than serve for tinea capitis (fungal infection), pediculosis (lice), open or inflamed scalp lesions, and unexplained hair loss.
Worked example
A client with relaxed hair requests a double-process blonde. Wet one strand and stretch it: if it extends and springs back, elasticity is normal. If it stretches and snaps, or stays limp and gummy, the hair is overprocessed and the service must not proceed - document the refusal and offer a conditioning service instead.