After dividing the hair into four sections, toner should be applied to the roots first, with a brush or plastic applicator. From the roots, the toner should be worked through the hair, but it should not be applied to any damaged ends of the hair until the end of the procedure. Toner is the second part of a two-part color process and is only applied after the hair is bleached.
Toners are used after bleaching to impart a more subtle or delicate shade to the hair. For instance, they can be used to give an auburn tint to brown hair, to turn blond hair to strawberry blond or to reduce the brassiness of blond hair. Using a toner with a blue, violet or green base helps to counteract brassiness, especially when covering gray. Toner can also be used to correct areas of over-bleaching.
Once toner has been applied, test the strands of hair often by stripping the toner to check the color. Often the toner looks a bit darker than the final color is going to be. Toner must be reapplied after testing. Typically toner takes 15 to 25 minutes to reach the desired color, but strands should be checked every five minutes.