Colouring and Lightening
What this domain tests
Colour theory applied to real hair: the level system, developer strengths, mixing ratios, application order, grey coverage, lightening, toning and the safety rules around patch tests and incompatibility.
Core rules
- Levels run 1 (black) to 10 (lightest blonde). Underlying pigment exposed on lightening: level 7 orange, level 8 yellow-orange, levels 9–10 yellow.
- Developer: 3% = 10 vol, 6% = 20 vol, 9% = 30 vol, 12% = 40 vol. Permanent tints are usually mixed 1:1; weakening the ratio weakens the result.
- Neutralise with the opposite: blue against orange, violet against yellow, green against red.
- Types: temporary, semi-permanent direct dye (no lift, fades in roughly 6–8 shampoos), quasi/demi, permanent oxidative (PPD/PTDS), high-lift tint, and bleach, which lifts melanin but cannot deposit colour.
- Patch test 48 hours before, per manufacturer; strand test for resistant, previously coloured or porous hair.
Worked example
Grey root retouch to a level 6 natural. Mix 30 g of shade 6.0 with 30 ml of 6% (20 vol) - a 1:1 ratio, 60 g total. Apply to the regrowth first, process about 20 minutes, then emulsify through mid-lengths and ends for the last 5–10 minutes, total 30–35 minutes. Reasoning: 20 vol covers grey and deposits tone without unnecessary lift, and the shortened time on porous ends prevents over-depositing and a darker band.
Traps that cost marks
No patch test; 40 vol applied to the scalp; altering the mixing ratio; lightening through already-coloured mid-lengths; forgetting to tone pre-lightened hair; promising a platinum result on level 4 hair in one appointment.