This is a one night only hair dye and even then you need to be thorough. I used this to go with a Wonder Woman Halloween costume. I had my mom apply it for me since she dyes her hair regularly and could apply it better than I could to myself. Im naturally a dirty blonde so it worked well although I did have a couple gray streaks where it didn't quite turn all the way black. As for washing out, it took the full 8 washes, I went gray first, then bluish and then slowly started seeing blonde again. I recommend it if you want to be dark for 1 night/day before washing. On a side note, be warned iherb.coms 1-3 day expedited shipping means Fed Ex ships it to your local post office and then they deliver it, not that would will receive it in 1-3 days.