The shampoo is wonderful for the job it is intended for... I first saw it at my brother's, who lives permanently in Germany, and I noticed that his hair was noticeably darker (Clarification: he has 60% white hair) but the coverage was very, very natural....
I have been using it consistently for a month now and I am one of the most difficult cases because my white hair reaches 95%. My hair is pure white, with a few dark ones at the nape of my neck...
I used it to see if it would break up this pure white a bit and after 5-6 uses the difference started to show in soft grey shades....
The whiteness is now a thing of the past and I have a mild, soft sandre shade that looks very natural and to someone who doesn't know you well, there is no noticeable difference in the overall appearance, but there is a noticeable difference to those who know you well and especially to yourself.
This is exactly what I was looking for... for a daily use shampoo to do the job without effort.
The manufacturer says to leave the product on for 2-3 minutes during washing and if you want more noticeable results to leave it on longer, and when you reach the desired shade you can take a break for a few washes.
I use it daily and on the first wash I leave it on for 3 minutes while on the second up to 5 (at the same time I take care of the rest of my body so I don't wait)
IMPORTANT: Don't expect to see results before the first 5-6 uses... but after that, yes... you will see! Also, it definitely works better for those who have 70% white hair or less. I recommend it 100%