Ok, so my under layer is black, and I really want to lighten it without damaging it more than it already is from dying it black. I've looked up all sorts of ways to do it, but I want the best technique. Can anybody help me?

I recommend using Loreal's ColorZap hair color remover, this color remover took me about one hour to lighten my entire head of hair that I have been dying black for over 15 years to a brassy orangish, yellow color. I then immediately took ION haircolor with a 30 developer on my hair, I believe the color was dark reddish brown and my hair turned out way lighter than it was , Only problem is I need to use a toner on it and calm down the brassiness.. I am thinking of dying it with a medium golden brown tonight to see if it will take away some of the red since I think it is too much,, but anyway, I have been trying for years to get this dark hair dye out and nothing would do it until this product... good luck