Hair Coloring and Chemical Texture Services
Color theory and levels
Know the law of color: primary colors (red, yellow, blue) combine into secondary and tertiary colors, and the color wheel predicts neutralization - blue cancels orange, violet cancels yellow, green cancels red. Hair levels run 1 (black) to 10 (lightest blonde); identifying level and underlying pigment at each level is the foundation of every formulation question.
Developers and lift
Developer strength controls lift: 10 volume (3%) deposits, 20 volume (6%) deposits with about two levels of lift, 30 volume (9%) about three levels, 40 volume (12%) about four levels with the most scalp sensitivity. A patch test 24–48 hours ahead and a strand test before full application are standard, and both are frequently the correct answer on exam questions about safety.
Application order
For a virgin (first-time) application, apply to midlengths and ends first, then the scalp area, so the heat of the scalp doesn't over-process the porous ends. For a retouch, apply only to new growth, then pull through the last few minutes.
Texture services
Relaxers are either hydroxide (lye) or thio (no-lye); both require a base cream or protective barrier, careful smoothing, thorough rinsing, and neutralization to restore pH. Retouch only new growth, typically every 6–8 weeks, and never relax over a previously relaxed strand. Curl re-forming and permanent waves follow the same reduction-then-neutralization logic.
Rule of thumb
If the client wants more than roughly two levels of lift, pre-lighten rather than pushing a stronger developer on the scalp.