To bleach hair that's been dyed black, mix the bleach, apply it, process the bleach for 45 to 60 minutes and rinse out. Depending on the target color, it may be necessary to tone the hair. Bleaching dyed hair takes roughly 2 hours and requires hair clips, powder bleach, developer, latex gloves, a color brush and a color bowl. If toning the hair, food coloring and shampoo are also needed.Continue Reading
Brush the hair. If bleaching long hair, segment it into three sections, and clip.
Pour the powder hair bleach into the color bowl. Measure out the recommended amount of developer. While pouring the developer into the powder, mix with the color brush. The bleach should be smooth.
Put on the protective gloves. Starting a half-inch from the scalp, apply the bleach using the color brush. If the hair is long, do not apply bleach to the last inch of hair until the final 15 minutes of processing time because that hair is more porous.
The length of time for processing depends on the desired lightness of the end result. Process for 20 minutes, then check a strand of hair. Continue processing, checking at five-minute intervals, until the target level is reached. When the hair is 10 minutes from the desired level, apply bleach to the roots.
Rinse the bleach out of the hair until the water runs clear. Shampoo and condition as usual.
Towel dry the hair, and check the color. If red or orange tones are present, use a toning shampoo. Mix a pea-sized amount of green food coloring with shampoo for red hair, blue coloring for orange. Apply to damp hair, and process for 10 minutes. Shampoo out.