Chemical Services (Coloring, Lightening, and Texture Services)
Core concepts
Chemical services questions test product chemistry, patch testing, and contraindications. Hair color categories: temporary (surface), semi-permanent (deposit, no lift), demi-permanent (deposit, low-volume developer), and permanent (lift and deposit via oxidation). Lightening uses bleach and developer to remove pigment; the level system (1 black to 10 lightest blonde) guides formulation. Texture services include permanent waves (reduction then oxidation) and relaxers (alkaline or thio-based), which break and reform disulfide bonds.
Traps to watch
- Patch test requirements: follow manufacturer and state rules; a history of allergic reaction means do not proceed.
- Strand test to predict timing and result, especially on resistant or previously treated hair.
- Contraindications: metallic salts, henna, recent relaxer, compromised scalp, pregnancy (refer to physician), and overlapping chemicals.
- Confusing developer volume with lift-volume affects processing, not just color.
- Forgetting ventilation, gloves, and eye protection.
Rule of thumb
Test first, protect the scalp, and never overlap incompatible chemicals. If hair has poor elasticity or the scalp is broken, stop and refer.
Worked example
A client with previously relaxed hair wants to go lighter. Check elasticity and porosity; if hair snaps, do not lighten. If healthy, strand test, use a lower-volume developer, and process with monitoring.