Hair Colouring and Lightening
The chemistry you must know
The natural hair pigment is melanin, of two types: eumelanin (brown-black) and pheomelanin (red-yellow). Lightening oxidises melanin, revealing warmth (red, then orange, then yellow, then pale yellow) as you lift. Colour products include permanent (oxidative, lifts and deposits), demi-permanent (deposits with low or no lift), semi-permanent (direct dye, fades out) and temporary. Developers contain hydrogen peroxide; 6 percent (20 volume) lifts roughly one to two levels, 9 percent (30 volume) lifts more, and 12 percent (40 volume) lifts most but stresses the hair. The underlying pigment you reveal must be neutralised by the toner you apply.
The consultation and testing
Always patch test according to the manufacturer's instructions before oxidative colour. Strand test when the history is uncertain. Record formula, developer, timing and result. Assess porosity, because porous hair grabs colour and processes faster.
Application and safety
Section neatly, apply to the correct zones, respect processing time, and check development. Do not mix products from different manufacturers. Wear gloves, ventilate, and avoid skin contact. If colour enters the eye, rinse immediately and seek advice.
Traps in questions
A common trap is thinking higher-volume developer always gives better results; it can cause damage and unwanted warmth. Another is forgetting that previously coloured hair may not lift predictably. Do not tone before lifting to the required level.
Rule of thumb
Lift first, tone second. Identify the level and underlying pigment, then choose the toner that neutralises it.