how long should i wait before i get henna wet
I recommend that you leave the mehndi on your skin for as long as possible - i.e. 4-6 hours, to achieve the darkest color, but remember that good henna will produce a reasonably brown stain after an hour. In any case, after at least 2 hours, scrape the mehndi off of your skin with a blunt knife or with your fingernails.