How can I make my Hair take Black hair dye?

I have colored my hair for over 15yrs blue black or darkest black, and I also chemically relax my hair once a year. Lately, I feel that my new growth doesn't take the hair dye like it use to, I have tried permanent semi permanent, maybe i am doing it wrong, any suggestions, or maybe a different brand?How can I make my Hair take Black hair dye?
I recommend leaving it on for a full hour- it wont damage your hair anymore than it would by leaving it on for 15 minutes.


Also- you should make sure that your hair is a little dirty when you dye it... if its clean it wont take the color wellHow can I make my Hair take Black hair dye?
i know it sounds silly but could ur hair be immune to the hair dye now?! try a different brand maybe..