Depends on what state the peroxide is in when you apply it. If it is just straight liquid peroxide you can just brush it on and keep applying it until the bone is white enough for your liking. If you are using the peroxide you mix with some other chemical (Mg maybe?) which turns it into a paste, you apply that and let it dry then just brush it off. When i used the paste i left it on for a week but could have taken it off earlier. I think you just leave it on until it is dry and flake off.