Quote Originally Posted by americangypsy View Post
The reason to have dirty hair is so that the color can be better absorbed by the hair shaft.When the hair has not been freshly washed and has been in the sun and blow dried the outside of the hair is open this is called the cuticle .This in turn allows the hair to more readily except the color .
well yeah...but any oils will have the opposite effect. Kaorte is probably right with the shampooing without conditioner the day before you dye it. Blowdrying is also probably not a bad idea.

I've self-dyed my hair like a zillion times and have very rarely had problems with it. And I've never waited until it got greasy.