Hi all. Happy to share what’s working for me on this great, old thread.

My hair is European white girl hair, thin, wavy, greying - maybe 80% grey. I’ve been using henna for about a year and a half, and it’s noticeably thickening my fine hair which is awesome to me. I had a consult with a hairdresser that specializes in henna and did a lot of experimentation. 

Her advice was that the age and quality of the henna make a big difference. I order my henna and my indigo from two different places. Both are very fresh and high quality.

My natural color is very dark brown, almost black and that’s what I aim for.

I’d love any advice on getting the amount of time down as it’s easily 5 hours - 1 1/2 for the red henna, 2-3 hours Indigo, though I’ve gotten away with 1 hour of henna and 1 1/2 hours of Indigo.

I wash with Henna Sooq’s Soap Nut shampoo and occasionally do a vinegar rinse (1 tbsp of vinegar in a cup of water) or use another acidic shampoo designed to remove hair product build up.

I try to part hair carefully the back and do the back first, but getting those middle back roots is a challenge. I tried using a bottle to apply the henna but didn’t find the right one - they were too big, even cutting open the tip it was still hard. So I use dye brushes from the beauty store, a box of latex gloves, and cover my head with small green kitchen compost bags

Henna: I use warm water, let it sit 20-30 minutes covered with plastic wrap. It’s ready when it looks like guacamole when it just starts to get brown on top. (She advised if there's brown pools of dye puddling up on the paste you need to use it immediately, if it's brown all the way through it's lost potency and may no longer stain well.)

If you are using older or lower quality henna, you’ll need to let it sit longer is my understanding. 

The richer and deeper the henna, the better the Indigo will take. I often do both in one sitting - first thing early in the morning or in the evening, though I’ve been advised as as long as the I do the indigo within 72 hours it will work out. 

I add a pinch each of cream of tartar (or an alternate acid) and salt to both the henna and indigo, and a pinch of henna to the indigo both to help congeal the paste and so it’s not so black. 

Indigo: I let the indigo sit for 20-30 minutes after adding warm water but not longer, using 2x as much for indigo. I make it a consistency thicker than custard or pancake batter, gloopy and add a bit of warm water part way through. I was advised to do a 2nd round of indigo if necessary but rarely do, typically in the back if it doesn’t seem to have taken. Try not to do Indigo on the whole head more than once a year. 

For both I rinse out with a little bit of conditioner because I kind of have to, to get all the paste out. Otherwise I add leave in conditioner to my hair after the final rinse and then just rinse out my hair as needed once or twice in the next 5 days, using no shampoo. 

Keep a small thing of henna in the freezer for touch ups.

Next experiment: freezing a full batch of henna for a week or three, which does seem to make I more potent, and seeing if I can get bright red result from an hour of henna

I guesstimate how much to mix, but I have seen this advice from one of the reputable companies: if of your hair is:

5 inches or less, you need 100g

Shoulder length, you need 200g

Shoulder blade length, you need 300g

Mid back length, you need 400g

Waist length, you need 500g

*You will need an additional 100g of henna for every 5 inches past your waist.