Blondify Your Locks
Tie up the top two-thirds of your bleached hair, letting the rest hang down. Coat the hanging strands in the blonde semi-permanent dye, using the applicator included in the box (or applying it straight from the squirt bottle). In some cases -- typically with semi-permanent dyes that last more than 20 shampoos -- you'll need to mix the color into the white developer bottle and shake it first.
Release another third of your hair, keeping the top third tied up. Coat those strands with the dye, then let out the rest of your hair and cover the remaining strands, until all of your hair is saturated with dye.
Give your hair time to soak in the dye for the time recommended in the dye's instructions.
Rinse the dye from your hair thoroughly, until the water runs clean. Stained towels are never in style -- though with a blonde hair dye, at least you don't have dark pigments to worry about!
Condition Your New 'Do
Apply a deep-conditioning treatment to your wet hair and let it sit for at least two minutes. Many semi-permanent dye boxes contain a deep conditioner that returns moisture to your tresses, leaving them soft and full of healthy shine.
Rinse the conditioner from your hair.
Let your hair dry. Air-drying is safer than heat styling, which can zap color from your strands over time. When it's totally dry, you'll be ready to rock your sunny new shade -- and stun your friends with your drastic blonde makeover!
Let a professional colorist bleach your black hair to a dark blonde shade, or even lighter. If you bleach at home you risk burning your scalp, missing spots and damaging your do in a major way. If you choose to take advantage of the bleach most blonde semi-permanent dye kits include, follow the instructions to the letter.
Don't rinse your semi-permanent color before the recommended time is up, or the dye might not take.