Perming and Chemical Texture Services
What this domain tests
The reduction–oxidation chemistry of perming and relaxing, rod and winding decisions, test curling and processing, neutralising, and the contraindications that make a service unsafe.
The chemistry
- The reducing agent (ammonium thioglycolate, pH around 9–9.5; acid perms with glyceryl monothioglycolate, pH 4.5–7) breaks a proportion of the disulphide bonds.
- Hair is wound on rods while soft; the neutraliser (hydrogen peroxide or sodium bromate) rebuilds disulphide bonds in the new shape.
- Rod size sets curl size; section size, tension, end papers and water content decide how even the result is.
- Relaxers use sodium hydroxide (pH 12–14) or no-lye guanidine hydroxide; they straighten and are neutralised with an acidic shampoo.
Safety and process
Test curl every few minutes - porous or previously coloured hair takes the lotion faster. Rinse thoroughly before neutralising, because neutraliser cannot stop a reduction still in progress. Do not perm bleached, relaxed, metallic-salt or visibly damaged hair; if in doubt, strand test and refuse.
Worked example
A strand test shows firm curl on virgin mid-lengths at 8 minutes but on the porous ends at 4. Plan: wind the porous ends last, apply lotion to mid-lengths first, check the test curl at 4 and 8 minutes, total processing around 12 minutes, rinse for several minutes, blot, then neutralise for the manufacturer's time. Reasoning: equal processing time on unequal porosity gives an uneven curl and over-processed ends.
Traps that cost marks
Perming over bleach; skipping the test curl; overwetting the hair so the lotion dilutes; uneven tension; neutralising before thorough rinsing; advising shampoo too soon.