As many people know, I am a fan of coloring my hair. It's a form of self expression and all that good stuff. Since my hair is naturally a thick dark brown (shh, don't tell my colleagues, they think I have no natural hair color), I have to bleach it before dying it most colors (except black). I'm not really a fan of salons because I don't like talking to strangers for hours, so I tend to do it myself. Since other people sometimes get inspired by my hair experimentations and want tips, I'm going to share my technique here.
First, when it comes to bleaching, I do not use one of those kits with pretty people on the front. The kits are handy because they come with all the supplies you need and very specific instructions, but I find that they are not very strong - even the ones that purport to be the strongest.
Instead, I start with bleach powder and 40 volume creme developer. The "volume" refers to the strength of the developer, and "40 volume" is the strongest that you'll find. I'm currently using Fudge brand developer and powder, which I got from the hair supplies shop at Harbourside Mall in Sydney, Australia. If you're in the US, you may want to check out Manic Panic's 40 volume bleach kit instead.
I then put on cheap latex gloves and mix 1 part powder with 2 parts developer in a tupperware container (leftover from too much takeaway). If you don't mix enough, no worries, you can easily mix more later.
Then I rub the mix over my hair, starting at the ends. Instructions always have you do the roots last, and as it turns out, that's because the chemicals process faster when they're close to the head, because your head is so warm and heats them up.
When I think that I've got everything covered (don't forget the back of your head), I go and watch a TV show for a half hour or hour. I'm used to the slight burning sensation of bleach so I tend to let it stay on for longer, but if it bothers you, you can rinse it out after just 30 minutes.
After I rinse it out and dry it, I check out how white it became, and if I missed any spots (not usually).
If it is still a bit yellow (as is natural with hair) and I am trying to dye it blue or just go for the very white look, then I wait for it to dry and then put a purple toner on it. A purple toner is basically a light purple hair dye that counters the natural yellow hues in human hair - so it does sometimes make your hair a bit purple-y if you overdo it (but I like that). I use one of two options these days: Fudge purple toner, or Schwarzkopf LIVE Color Silver toner.
If I really care about maintaining the whiteness of the color, then I sometimes invest in toning shampoo, which is basically like shampoo with a little purple hair dye in it.
And that's it... happy bleaching!