This is a great product and has worked for me in the past, although recently i am having issues around yellow tone coming through my blonde foiled hair. I use this once a week, but might try leaving it in for longer, or maybe using it twice a week.
This has had such amazing review I think its maybe because i'm not using the product properly.
This is my favourite violet shampoo, after trying many. It tones down brassiness after one use. I like to leave it on for around 3 minutes to give it extra time to work. I only need to use it once a week to keep my hair non-brassy. I highly recommend this product!