PROS AND CONS OF PERMANENT
Well I guess the fact that it’s called permanent might give us a hint there. Once it’s in you’re pretty much stuck with it until it grows out. On lightened hair it will probably fade quite a bit but the overall shade remains. Permanent dye penetrates into the hair shaft and deposits pigment rather like a tattoo needle does under the skin. So it’s not washed out but can fade over time.
PROS :- Far more choice of permanent shades for blondes. All major brands have a very wide choice and range. There is no constant colour change like with semi-s, semi’s fade very quickly. Permanent dyes are less high mainteance than semi’s.
CONS :- Make a mistake and it’s very hard to correct it if you decide you don’t like it. You certainly don’t want to be putting your hair through all this again too often. Also it means more work for touching up the roots as they will have to be separately pre-lightened and then ONLY the pre-lightened roots get an application of the same shade of permanent dye. As you can imagine this can be tricky and you may get bits of ‘colour’ overlap between root and previously coloured area.