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Nothing ruins knockout color like dark roots. Sure, a few weeks' worth of root regrowth is OK. You can change the part, pop in a few curls -- you can hide those suckers. But once you pass the four-week mark, you're pushing it. Most stylists recommend touching up your color every four to six weeks, but since blond creates such a contrast between the roots and the dye job, it's best to stick to the four-week rule.
Feel your hair. Is it 100 percent dry? If not, get it there. If there is any moisture whatsoever, you're going to have a heck of a time pulling hair through the cap.
Put the cap on your head and tie it in place. Pull strands of hair through the holes on the cap with the frosting needle. Slide the needle in at an angle and snatch a strand of hair with the hook on the end. Pull the hair through slowly to avoid tangles.
Blend equal parts hair-lightening powder and 30-volume color developer together in a color bowl. Brush the mixture on your brown roots, lifting your hair up in sections as you go. Don't put the color on the blond portions. You've already lightened it once; to do it again would only be asking for your hair to fall out.
Place a plastic cap on your head and set a timer for 15 minutes. Direct an even flow of heat from your hair dryer over the outside of the plastic cap. It's very easy to heat one spot more than others with this method. Pay attention to the temperature of the cap. And don't get too close! Plastic melts.
Check your color. Lift the cap and rub away a bit of the lightener. Does the color match the rest of your hair? If so, great! If not, dab some more color on the spot you checked and wait another five minutes. Keep checking it until you get it right.
Remove the plastic cap, but keep the frosting cap in place. Allow warm water to run over the outside of the frosting cap, rinsing away all of the lightener. Put a little bit of shampoo on your lightened strands and gently remove the frosting cap. Shampoo and condition.
Pulling hair through the cap can be a chore. A little bit of silk serum through your hair before you put the cap on works wonders. The silk helps the hair glide through the holes and prevents tangling under the cap.
Banding is a common problem with highlights. Banding occurs when the cap slides, preventing hair at the base from lightening properly. Keep that cap tied tight to prevent it.