I have used henna for about 25 years. I came up with a new mix for my waist-length gothic raven-black-cherry hair to cover the gray that is now about 33%.

1 cup Ancient Sunrise henna mixed with a mildly acidic liquid mix and 1 cup Ancient Sunrise indigo.

Mix all liquids and henna. mix thoroughly and continue mixing for about 3 minutes. loosley cover bowl and let stand over night.

One hour before using, mix the indigo with distilled water in a smaller bowl (let water stand 3 minutes before adding the indigo) and let indigo paste stand 30 minutes uncovered. then add indigo and henna mixes together and blend thoroughly. Put some of the mix in your cone bag and knead lightly, flattening it and letting it rest on a heating pad on low for about 20 minutes. make as many cone bags as you can fit on the heating pad at once and now cover the bowl with the mixture in it tightly until it is used up.

Use your favorite technique to apply this and wrap in a plastic bag and towel. I leave this on for 3-6 hours without heat. I have in the past used heat for 1 hour and cut my remaining processing time in half. This will take about 4-5 days to completely develop and oxidize into the final shade. I get a nice shiny black with plum-burgundy-garnet highlights.

Some tips I have discovered thru the years:

• Paint your nails the day before you henna--dont worry about neatness, in fact get your cuticles covered in polish too--it will protect your nails and fingers from staining(unless you want them to stain!).
• Use talc or cornstarch on your hands before you put on your gloves! this will absorb some of the perspiration that might develop as you are sticking your hands into the gloopy warm henna mess(I mean mixture...wink).
• Be prepared for a mess if you attempt this alone! (no wonder persian princesses lived in harems!).
• Start applying from the crown with your head bent forward--taking a 1 inch part at a time.! If this is too much like sticky baby poop mixed with concrete add more hot water or half a bottle of your favorite conditioner. to rinse out of waist length hair. You gotta fill the tub and just lay back and float for about 10 minutes before you can even think about getting it loose.
• Don't scrub your hair or ! move around, just soak. Put your feet and legs up out of the water if you can't fit well. (personally I feel somehow refreshed and 'cleansed' after soaking my whole body in the henna tub for 10 minutes. but--you will have a slight yellow tinge for a day or two..LOL).
• Rinse and scrub the rest out in the shower. If it's summertime or warm enough, use the hose in the yard (works especially well for the cold rinse).

Notes and References
Henna: https://www.mehandi.com/Mehandi-com-Ancient-Sunrise-Henna-for-Hair-s/121.htm
Don’t have fruit juice on hand? Keep some fruit acid powders in your cupboard.
Mildly acidic liquid: https://www.mehandi.com/Fruit-Acid-for-henna-dye-release-s/299.htm
More info on mildly acidic mixes: https://www.tapdancinglizard.com/henna-and-acidic-mixes/
Ancient Sunrise henna for hair kits with everything included: https://www.mehandi.com/Mehandi-com-Ancient-Sunrise-Henna-for-Hair-Kits-s/124.htm
Henna color oxidizing ("rusting"): https://www.tapdancinglizard.com/mixing-and-testing-your-henna-mix/ pp.25-29

Video How-To
Mixing henna and Indigo: https://vimeo.com/manage/videos/561559371a>