I'm a 30 year old indian female and have been using henna for coloring my hair for grey coverage for the last 3-4 years. I have recently also tried using indigo to shade it black.
I notice in the last 3-4 months, when i just apply henna after freshly shampooing hair, the henna stays in the roots in the orange color just until the next hair wash only. The roots of grey hair (few that I have) on the top of my head and front side, becomes white within one hair wash (grey hair turns white 1cm from root) and the remaining grey hair has the henna stain still in places (until few more washes).
I'm not sure what i'm doing wrong that the henna at the grey roots washes away in one hair wash. Earlier to this in past few years, the henna used to stay in my grey roots atleast 3-4 weeks(upto 6-8 washes).
Procedure that i follow:
Henna bought from mehendi.com - mixed with brown tea water to get darker stain and leave it mixed overnight.
Wash hair in the morning and apply the henna and leave it on for 4-5 hours.
Wash off the henna in hair and apply conditioner.
This procedure that i follow, the henna at the grey roots (for some grey hair i sport) washes off to a centimeter from root within the next shampoo wash.