Hair Coloring and Lightening
Core concepts
Understand the color wheel, levels (1–10), and undertones. Know the difference between temporary, semi-permanent, demi-permanent, and permanent color, and how developers (10, 20, 30, 40 volume) affect lift and deposit. Know the law of color (primary, secondary, tertiary) and how to neutralize unwanted tones. Lightening uses bleach/lightener plus developer; the hair goes through stages of lift (red, red-orange, orange, yellow-orange, yellow, pale yellow).
Traps to watch
Questions test developer choice: 10 volume deposits, 20 lifts one to two levels, 30 lifts two to three, 40 lifts more but increases damage. Never use 40 volume on the scalp for lightening. Do not confuse semi-permanent (no lift, deposits only, fades) with permanent (lifts and deposits, requires patch test). Always patch test 24–48 hours before color, especially with permanent or oxidative dyes. Do not lighten over metallic salts or henna without testing.
Worked rule of thumb
To neutralize yellow, use a violet-based toner; to neutralize orange, use blue; to neutralize red, use green. Choose developer by desired lift and scalp sensitivity.
Safety
Wear gloves, ventilate, avoid skin contact, and follow manufacturer timing. Stop if burning occurs.