Pour 1/8 cup of bleach powder into a plastic bowl. You seriously may want to tie a scarf around your nose and mouth all bank-robber style. Alternatively, wear one of those paper masks people sport when they're afraid of anthrax attacks in the subway, as bleach powder is some pretty gnarly stuff that likes to fly up your nostrils and make you sneeze.
Pour in 1/8 cup of 20-volume hydrogen peroxide liquid developer. Developer may be creamy and opaque or watery and clear. Either one will work.
Add 1/4 cup of clarifying shampoo, the kind designed to strip all the gunk out of your hair. Liquid castile soap diluted 50/50 with water also works well.
Put on a pair of latex gloves and start to work the bleach mixture through your hair with your fingers. It will lather up a bit due to the shampoo, but try to keep it off your scalp as much as possible, as bleach can cause a burning sensation.
Cover your hair with a plastic shower cap and peek underneath it every three to five minutes, to make sure the color's falling out. Make sure your hair isn't. Leave a soap cap on for up to 15 minutes, never any longer.
Rinse well. Wash with another dose of plain clarifying shampoo and follow with a deep conditioning treatment to restore lost moisture.