Services: Chemistry, Consultation, and Technical Judgment
Know the structure behind the service
Most service questions reduce to structure and chemistry. Hair has three layers - cuticle (protective outer scales), cortex (bulk, pigment, and disulfide bonds), and medulla. Wet hair stretches and is more fragile; bonds are broken by chemical services and must be rebuilt. Normal skin and hair pH sits near 4.5–5.5, which is why alkaline services must be followed by an acid-balanced product.
Chemical services and their tests
Oxidative (permanent) color requires a patch test for aniline-derivative tints, generally 24–48 hours before the service, on each new client or after a reaction; a strand test predicts color or relaxer outcome. Hydroxide ("no-lye") and thio relaxers both require strand testing, protection of the scalp, and thorough neutralizing, which lowers pH and rebuilds disulfide bonds. A neutralizer does not "shrink" or "seal" hair in the marketing sense - it restores chemistry.
Consultation and contraindications
Every service starts with a consultation: history, prior chemical services, allergies, medications, and scalp or nail condition. Contraindications - open lesions, inflammation, unexplained nail discoloration, a prior reaction - mean decline and refer. Nail services require knowledge of the nail plate, cuticle, and lunula, and a strict no-cutting of live tissue.
Traps
The exam rewards the conservative answer. If a client reports burning during a relaxer, the correct move is to remove the product and rinse - not to "add more base" or wait it out. If a patch test is positive or was never done, the service does not proceed.
Rule of thumb: test before you treat, and when in doubt, stop and refer.