Hey group I posted yesterday about my hair coming out too dark with the sunrise dark brunette mixed with amla.  Well I search this forum for how to lighten and found an old post on using vitamin C to lighten the hair and so far so good.  I crushed up some vitamin c (12 tablets of 1000mg) mixed it with cheap shampoo, wrapped my head in plastic for an hour 45minutes, and it did significantly lighten it up--I was pleased. 

Now I am wondering how long it will last or will I have to periodically use vitamin C to keep the effect since I heard the henna-indingo will continue to change with oxidation and it may return dark again.  Any thoughts?