Chemical Services (Coloring, Permanent Waving, Relaxing)
Color fundamentals
The level system runs 1 (black) to 10 (lightest blond), each level representing a step of melanin loss. Developer strength drives the result: 10 volume (3%) deposits, 20 volume (6%) lifts roughly one to two levels and gives dependable grey coverage, 30 volume (9%) lifts two to three levels, and 40 volume (12%) delivers maximum lift with maximum scalp irritation. Know the law of color - primaries, secondaries, tertiaries - and that complementary colors neutralize unwanted tone. Underlying pigment is always exposed when you lighten, which is why cool formulas are chosen against warmth.
Perms and relaxers are the same two-step logic
Both reduce and then rebuild disulfide bonds. Ammonium thioglycolate (or glyceryl monothioglycolate) reduces; the neutralizer - sodium bromate or hydrogen peroxide - oxidizes the hair back into its new shape. Relaxers straighten with a high-pH cream: sodium hydroxide (lye), guanidine/calcium hydroxide (no-lye), typically finished with an acid-balanced neutralizing shampoo. Rod diameter and wrap pattern (croquignole, spiral, bricklaying, piggyback, bookend) determine curl size and direction.
Mandatory tests and timing
Patch test 24–48 hours before any aniline-derivative color. Strand test for timing and result. Apply relaxer retouch to new growth only, never pull relaxer through previously relaxed hair. Do not relax over metallic dyes or over broken skin, and space relaxer and permanent color at least two weeks apart.
Worked example
A client with 60% grey wants solid, opaque coverage at her current dark brown level. Use permanent color at her level with 20 volume and full processing time; dropping to 10 volume often leaves grey translucent, and pushing to 40 volume only adds lift and irritation.