Part your hair down the center of your head using a rattail comb. The part should be from your bangs all the way to the nape of your neck.
Make another part from the top, middle of your head, down behind your left ear. Make another part from the top, middle of your head, down behind the right ear. Your head should contain four sections of hair. Two sections in front, two sections in back.
Clip up all four sections to get them out of the way. You will apply the bleach to your roots one section at a time. It may sound a bit time consuming, but applying the bleach any other way can lead to blotching or unnatural-looking tiger stripes, which is probably not what you're going for.
Empty a packet of hair bleach into a plastic bowl for short to medium hair. If your hair is long, meaning below your shoulders, you will probably need two. Don't skimp on the bleach! You don't want to run out with only half of your roots done.
Pour 20-volume peroxide into the bowl with the bleach. Add just enough to make a thin paste, stirring as you pour. Use a hair color brush to stir the two together. Does the bleach and peroxide look like white pancake batter? If yes, your're ready to move on.
Fill the bristles of the hair color brush with bleach. Don't blob it on or you will just make a big mess. Fill the bristles generously, but don't overdo it. Remember those parts that you made -- one down the center and one behind each ear? This is where you will begin bleaching your roots.
Slip on a pair of rubber gloves and brush the bleach onto the new growth along each part. The new growth is the new hair that has grown in since your last color. So, brush the bleach on trying your best not to overlap the line of demarcation between the new growth and the hair already bleached.
Begin bleaching the sectioned areas. Remove one clip and let the hair from that section hang free. Now, for the tedious part: Look at the shape of the hair section. It looks like a piece of pie, right? Starting at the top of your head -- pointed part of the pie section -- create a horizontal part with the tail of the rattail comb. The part should be no thicker than 1/4 inch.
Hold the section with your fingers and brush the bleach onto the new growth located on top of the section, and then lift the section up and lay it along your crown -- the top of your head. Bleach the new growth under the section. Create another horizontal part just below the one you made previously. Just like before, paint the bleach onto the new growth on the top and the bottom of the section. Make another part below that one and do the same.
Remove the next clip once you complete bleaching the roots of the first section. Repeat the process all over again. Remember -- part, bleach top and bottom and then make another part below it. Keep it up, you're doing great! When you finish bleaching the roots of each section, pop on a plastic shower cap, sit back and chill for a while.
Read a magazine or watch your favorite soap for the next half hour. Set a timer if you think you will lose track of time. Once the timer screams 30 minutes, check your roots. Do they rock or do they need just a few more minutes? If your roots still need a little more processing, occupy yourself for another five or 10 minutes then check again, but do not leave the bleach on for any longer than 45 minutes.
Wash the bleach out of your hair immediately, when the color is right. Give your hair two good shampoos with a moisturizing shampoo, followed by a dose of moisturizing conditioner. Dry and style your new blonde locks. Awesome job, Blondie!
There is no need to wash your hair before bleaching your roots. Dry, unwashed hair is best.
Purchase bleach and peroxide separately at the beauty supply store or buy them together in neat little kits that you can find right in your supermarket!
Do not bleach your scalp. The bleach is meant for your hair, not your skin. Bleach applied directly to your scalp can cause burning and irritation to your skin.
If your scalp feels like it's burning, wash off the bleach immediately. If the burning keeps up, see your doctor.