How do I get to a 9.1 from a12.11

Definitely got to bleach it. And use a 40 volume developer, which, both mixed together, can be very dangerous lol. Know how fast your hair processes, always keep a close eye on it, and be careful not to scorch your scalp. I've gotten blisters and open sores on my scalp from bleaching and they are not fun. If you can, go to Sally's and ask for a soothing serum to mix in to your bleach. The soothing serum will ease the burn. There is also the option of doing a soap cap. You get a processing cap, mix bleach, developer, and shampoo in your color bowl, then apply it to your head & put the cap on for the time needed to process. Its helps a sensitive scalp, but you can still get burned from one. Good Luck!