When adding color to hair, a shorter application time generally yields a lighter result since the dye has less time to absorb. When bleaching hair, however, leaving the product on longer yields the lightest results.
To go significantly lighter, it is necessary to use a hair lightening or bleaching formula. For optimal effect, experts discourage going more than two shades lighter than the natural hair color. Furthermore, following product guidelines for application time is the best way to avoid damaging hair. Typically, lightening products are left on hair for a minimum of 20 minutes and a maximum of 60 to 90 minutes, depending on the formula. Performing a strand test is the best way to get the desired look.