Hair Coloring and Lightening
Level and tone
Color is described by level (lightness, 1 black through 10 lightest blonde) and tone (warm, cool, neutral). The law of color governs mixing: primaries combine into secondaries, and a color opposite on the wheel neutralizes its counterpart - blue cancels orange, violet cancels yellow, green cancels red. Lightening exposes warm contributing pigment in a predictable order: red, red-orange, orange, orange-gold, gold, yellow, pale yellow. That is why a lift of more than two or three levels almost always ends with a toner.
Categories of color
Temporary color coats the cuticle and shampoos out. Semi-permanent color deposits only, uses no developer, and fades over several shampoos. Demi-permanent color deposits with a low-volume developer and lasts longer. Permanent color lifts and deposits using aniline derivatives and requires a patch test 24-48 hours before the service. Developer volume controls lift: 10 volume deposits, 20 volume lifts roughly one to two levels, 30 volume two to three, and 40 volume three to four but is generally kept off the scalp.
Application order
For a virgin application, apply to midlengths and ends first, then the scalp area, because scalp heat accelerates processing. Retouch applications go to new growth only; overlapping permanent color on previously lightened hair causes breakage.
Traps
Semi-permanent color does not lift. Developer alone does not lighten - the alkalizer plus peroxide does. A filler is not optional when going darker over lightened hair; without it, the result turns muddy or green.
Rule of thumb
Choose developer strength by the number of levels of lift required, and never ask 40 volume to do 20 volume's job.