Depending on your natural hair color (mine is dark blond), your desired color (a medium red), and developer (20vol) you wait 20-30 min or so and then wash out the bleach. i think using a hair dryer on warm will speed it up, but thats just a guess. take out a foil and see if your hair looks good. then wash it out completely. because its just a bleach step, hair will be 'brassy'