BY SALLY MADISON
NATIONAL COLOR TRAINER
Which developer strength do I use when coloring?
It all depends on how many levels you are intending to lift by.
And there are essentially 3 different cases here.
Case no 1: When you are using regular color
When using regular color use 20 Vol developer when you need 1-2 level lift and 30 Vol when you need 3 levels lift.
Case no 2. When you are using high-lift color
When using these, use 30 Vol developer for maximum lift. You should be able to achieve up to 5 levels lift by doing this.
Case no 3. When you are using bleach
When using bleach, use 20 vol for 1 -3 levels of lift.
And use 30 vol for more than 3 levels of lift.
Should I ever use 40 Vol developer?
Only use 40 Vol for very very stubborn hair that is truly difficult to lift.
For example, if the hair has been colored dark with box dye, then an initial application of 40 Vol developer may be necessary.
Should I tweak the amount of developer to get more lift?
Never do that. Just follow the instructions above, only use good quality products and you should be fine.
If for some reason you have not got to the hair color level you were targeting after one round of bleaching, simply do a second bleach application.
Use only 20 Vol developer when doing so.