Chemical Services: Haircoloring, Waving, and Relaxing
The chemistry in one paragraph
Hair is held together by disulfide, salt, and hydrogen bonds. Chemical services either deposit color or break and rebuild those bonds. Permanent color and lighteners raise the cuticle with an alkaline product and use developer (hydrogen peroxide) to lift natural pigment and deposit new pigment. Volume matters: 10 volume deposits, 20 volume lifts roughly one to two levels, and 30 or 40 volume lift more but are not "stronger color." Demi-permanent uses low-volume developer and no lift; semi-permanent stains the cuticle and fades out.
Relaxers
Hydroxide relaxers (sodium hydroxide, "lye") and no-lye relaxers (guanidine, calcium hydroxide) straighten by breaking disulfide bonds. They are not neutralized by rebuilding bonds; they are stopped by thorough rinsing and an acid-balanced shampoo. Retouch product goes on new growth only - overlapping already-relaxed hair causes breakage and scalp burns. Never relax abraded skin, and never scratch or shampoo immediately before a relaxer.
Waves
Ammonium thioglycolate alkaline waves process at room temperature and are stopped with a neutralizing lotion; acid waves need added heat. The neutralizer is not shampoo - it rebuilds the disulfide bonds the waving lotion broke. A test curl shows whether processing is complete; a strand test shows whether the product is safe for this hair.
Universal safety
Patch test 24–48 hours before color or lightener on a new client, read and follow the label, record the formula, wear gloves, and ventilate. If a client reports burning, stop and rinse - do not wait it out.
Rule of thumb: if the hair has had two or more chemical processes, test before adding a third.