I used NI for 10+ years. At first i would leave on for the recommended 20min...... then i gradually went to 50min. A stylist told me that for stubborn grays, Id need to go that long. It never hurt my hair at all and would last 2-3 weeks or longer, until my roots grew out.

Try leaving it on 30min and see if that works for you. And I agree, the condish that comes with it ROCKS!
3a long thick -botticelli hair when there is humidity
2c wavy w/curls if there isnt.
currently using Bioterra & KMF in winter
Jessicurl styling in summer
Natures Gate poo & condish
Thank you NC for bringing me back to curly!