I just used this as I was getting ready for work, (I was running late) and thought, "Oh, I can't shower, this will be perfect!" I was wrong. I waited the time, and still, the white residue didn't come out. I had to put my hair up in a high bun to try and hide some of the residue that wouldn't come out, (even when I put a bit of water on, it wouldn't come out.) It did work, but the residue was a no-go for me. Also, holy loud noise when you use it. It woke my boyfriend up in the other room, and said, "what the heck was that?!"
This would probably work best with people with blonde hair, not a dark brunette like me, if it leaves this residue.