I have never used it but I have heard bad things about processing your hair over it. Be careful. I would talk to a beautician about it before you use it.
Stay away if you ever plan on highlights or perming. It is semi metallic and when another chemical is placed over it it can heat up.
I had a case where a girl used it and too dark , said it was clairol.
Her hair started smoking.I pretty much threw her into the sink. No blonde highlights for her.