How soon can i re-bleach my hair?

well it depends on what kind of blonde you want. you don't have to wait 14 days to redo it i would try it anymore for tonight.. how long did you leave it on the first time? how blonde do you want it? you should be careful 30 is a really high peroxide and can be very damaging. the best thing to do is to go to the salon. because dark or black hair is difficult even for a hairdresser to get it to a perfect blonde. the lightest your hair will get with 30 vol is orange. and it will break off if you leave in on too long. a professional can make it nice cause there are special toners/glazes to change the tone of the highlighted blonde.