It depends on how dark your natural hair is. If your hair is between a dark blonde to med brown, you should always use a 20 volume peroxide, and it can take 5 minutes to 20 minutes,under a hair dryer, or put a bag on your hair and heat it up with your blow dryer. If your hair is darker, you need to use a 30 volume, or the color may never get beyond a orange gold color, and then it could take up to 1 hour, after that it stops processing, then you need to re-apply a new batch. If your natural hair is in the 1st category, you shouldn't have any problems, but if its darker BE CAREFUL...Hairsylist for 15 years.
