DO NOT BLEACH YOUR HAIR IF YOU HAVE RELAXER IN YOUR HAIR. By this, I mean ever. If you relaxed your hair 6 months ago and it's mostly grown out, that still counts. If it has not been cut out, then you can't be putting bleach on that. Bleaching where you have relaxed will break it. Off. Like all your hair is in the sink. Seriously.
Generally speaking, lift usually means bleach. You can also use what's called highlift color which is good for going a few shades lighter, but ONLY on natural hair, not other colors. In your case, you'll definately need bleach. Just putting developer on by itself before coloring is called presoftening. It's what old ladies get because it lifts the cuticle and helps the color to stick better to their gray hairs. Not what you want. Because your hair is black, it will turn orange as it's lifting. It will go black-brown-godawful orange-pretty orange-gold-yellow-then finally white. You don't really want to bleach it all the way to white. That will break your hair. It will in fact lighten based BOTH on time left on, and on developer strength.
Developers go like this:
10volume-Used for deposit only. Does not lift.
20volume-Used for general hair color. Gives 2 levels of lift at most.
30volume-Used to lift. Gives 3-4 levels of lift.
40volume-Gives the most lift. Very rarely used because it's very easy to break one's hair with 40.
This is what I would do: Start with the bleach where you want your hair the lightest, which would be the ends. Make sure it's good and saturated and keep an eye on it. The bleach should have directions. Read them. Once you've finished applying to the ends (but have not begun your processing time yet) start applying the bleach to the second lightest area. This stagger in application means that your ends will always be a couple steps ahead of the rest of your hair. Keep an eye on it. I would do 20 volume and a processing time of something like 45 minutes, and you will probably want to use heat to speed up the process. This means, put a plastic grocery bag over the hair that has bleach on it, and run the blow dryer set on hot over the bag. You have to put something between your hair and the heat because the bleach will dry out and damage your hair if you don't. But seriously, you need to be checking it every five minutes. You only want to lift it to just lighter than the color you want on it. Anything more than that is just damage for no good reason. So it looks to me like you can stop it in the orange-ish stage. Keep in mind that when the bleach is on, it will look a lot lighter than it actually is. To check the color of it exactly, scratch the bleach off a small part of hair with your gloved finger nail until you see just the hair. If that piece of hair looks a bit lighter than the color you want on it, and the rest of your hair looks about the same, then shampoo it out.
I also strongly urge that you check the ingredients in the colors you have picked out to make sure there's no kind of any metals in it (copper, silver, nickel, etc.). This is because any kind of metals on the ingredients list in hair color means it has metalic salts in it. These cause a lot of problems including damaging your hair. If you go to Sally's, some of the colors they have don't have metalic salts in them. You can ask the ladies there what exact developer goes with what color, but you'll need a 20vol for both colors (and you can't just use your bleach developer).
I think that covers everything. HTH.
