Let’s see, for red hair, I would say about an hour and for dark brown hair to black hair I would say about an hour as well. Red hair also is going to be more orange when it’s bleached. Unless you do it, you bleach your hair two or three times. I know, with my hair, I went from red hair to blond hair; I had to bleach my hair like three or four times to get it to an actual blonde color that I can work with, with the toner to make it white. If you’re planning on going from a dark color to a white blonde, be prepared to just bleach your hair a lot, maybe three or four times. But the only things I want to say about that is don’t bleach your hair three or four times in three or four days. Bleach your hair once, wait about a week, you never know what the color will end up like. When I bleach my hair, or when I do my hair, I never judge it by the color that it is, the day I wash all the bleach, or all the color, or all the toner out. I always wait a few days because you never know what color it’ll end up and you might actually just like the color it’ll end up. It might lighten up, it might darken, and you never know what your hair is going to do. So I always judge it by about a week or a few days.