Chemical Texture Services (perms and relaxers)
Bonds and chemistry
A curl or a straightened strand is really a rearrangement of disulfide bonds. Perm solution is a reducing agent - ammonium thioglycolate is the classic - that breaks those bonds; the neutralizer is an oxidizing agent (hydrogen peroxide or sodium bromate) that rebuilds them in the new shape. Traps: the neutralizer does not condition the hair, and it cannot be skipped or shortened without risking curl relaxation. Alkaline waves sit around pH 9.0-9.6 and rely on wrapping tension; acid waves sit around pH 6.5-7.0, use glyceryl monothioglycolate, require added heat, and generally produce a softer curl with longer processing.
Relaxers
Hydroxide (lye) relaxers run pH 12-14 and process quickly; no-lye versions (guanidine, lithium) run at a lower pH but are not automatically gentler - they can leave mineral buildup and dryness. Thio relaxers use ammonium thioglycolate around pH 9.5-10.5. Relaxers are not neutralized the way perms are; they are thoroughly rinsed and followed with an acid-balanced shampoo or normalizing solution to lower pH and remove residue. Virgin relaxer application goes to midlengths and ends first, scalp last; a retouch goes to new growth only.
Hair analysis and timing
Porosity, elasticity, density, and texture determine both product strength and timing. Perform a patch test and a strand test, and check a test curl every few minutes rather than trusting the clock.
Worked rule of thumb
If a client was relaxed two weeks ago, do not perm - most manufacturers require the relaxer to settle and a strand test to pass before any thio service. When in doubt, the answer that protects the integrity of the hair is usually correct.