Thank you to all of you
More questions, i didn't understand everything ( english is not my native language)
just for information my piece is not dark it is blond but not blond enough for my hair...

to paul : where do i find " [weak] solution of fabric-dye remover" to try this solution ?
and what is Creme Peroxide for ? just to mix with the wella color ?

to Hairscare and Hersute : what does "bleach the dark hair first " mean ? how do i do this ?

So for my next piece it is better for me to order a very light blond (or even white ) hair and dye the piece with the color i want ( which i buy in the store ? )
thanks a lot guys
happy new year 2012 to evryone