I lightened my hair using one part vitamin C to two parts clarifying shampoo - (4 tablespoons vit c and 8 tablespoons shampoo).
Mix the two until frothy, then apply to dry hair covering thoroughly. I then covered my hair in plastic and waited 2 hours until washing out. Shampooed again and conditioned well.
Before picture.
This is the after picture.
The lighting conditions of the pictures are identical so you can see the difference.
This treatment didn't lighten my hair that much, but it did remove some of the darker dye from the lower parts of my hair.
My hair looks shinier, healthier, and some of my natural red tones are more noticeable.
The vitamin C did not dry out or damage my hair.
I purchased the vitamin C from a health food store for $2.50 so it was a inexpensive treatment that showed nice results.