Some of you inquired about how long "coverage" last with the henna/indigo treatment. For me (and I can only speak for myself), my few strands of gray remained stained black for about 5 weeks. Since I generally do a henna treatment about once a month this works well for me, but I think I will try doing a rinse after I use up my last batch of indigo to see what those results are like.
For those of you who don't know what a "rinse is, here's a brief description:
A hair color rinse deposits a temporary color on the hair. It can deepen the color, add shine, or refresh existing but "blah" color. It doesn't lighten hair because it contains no peroxide,nor do they contain ammonia. They usually last up to 8 shampoos before you have to reapply.
Rinses are safe because they only deposit color on the hair shaft similar to henna.