There are actually several methods to break the base, of which only one will be discussed in this post. First, I’d like to explain what the expression means. Breaking the base means simply to lighten the existing level of hair 1 to 2 levels. The easiest way to achieve it is to use a decolorizing (corrective) shampoo, which is basically a mixture of shampoo, lightener (bleach) and developer.
Here’s how to mix it:
1 part bleach
1 part 20 or 30 volume developer
1 part shampoo
Mix the ingredients together and apply quickly to hair. Then, you’ll have to watch carefully as the lightening action can occur quite rapidly. When it’s done, wash the hair and you are ready to color over. As you can see the idea is to make bleach mixture liquid enough so you can apply it quickly to the hair. Some versions of decolorizing shampoo make you use conditioner, some make you add water. I don’t recommend adding water because it’ll just dilute the developer. Shampoo will dilute it too but at least it’ll add detergent action by surrounding the hair with a mixture.