I wear a lot of bleached out clothing, In fact so much i'm quite sure my boyfriend think I sit in our bathroom sniffing bleach when he's out. Thats beside that point though, I always get asked "how do you do that?" "How do you know what colour it will end up?" or "How much bleach do you use?"
Truth, I never really know what colour things will end up. I usually have a pretty good idea but i've been pleasantly surprised and totally disappointed.
Part 1: Lightening
Blue Denim is probably the easiest thing to bleach, I've only ever experienced it fading to a lighter blue or becoming white if straight blench is applied to it. Black denim can fade to grey, turn a peach or yellow colour, I even had a pair of black jeans become a acidy blue green colour. If your a novice bleacher I suggest starting with an article of blue denim.
A deep pot or bowl
I usually use approximately one cup of bleach for ten cups of hot tap water
Mix the bleach and water into your pot or bowl.
Wearing your rubber gloves add the piece of clothing you are bleaching to the water, swishing it around so every surface is evenly soaked. You want to make sure there is enough water in your container so that none of the material is sticking out of the water. If you need to add more water for this, remove the article of clothing, add the appropriate amount of water and bleach using a 1-10 ration again. Mix the solution around then add the clothing back in.
Then your going to allow the piece of clothing to soak for at least an hour or until it reaches your desired colour. Wearing your gloves try to swish and squish the material around every 15 minutes so it lightens evenly.
Once your desired colour is reach, wearing your gloves remove the clothing for the solution and throughly rinse with clean water. You could also put it through a washing machine cycle, but make sure the load has only white clothing in it. Then dry.