Most people have very absorbent hair, which helps the dye last longer and keeps the color fresh. Then all you need to do is touch up roots as need and not do the entire head. In many cases doing the entire head can make you hair darker over time, so you really want to concentrate on the roots when doing browns or mahogany. If you are one of those that have stubborn gray's (not so absorbent) or color that is not lasting, here is a tip a customer actually called in and then posted on line. She said she has done it for about 4 years and only done her roots once a month using a mahogany with a small amount of burgundy mixed in.
Here is her method:
Awesome product- I’ve been using this henna on my hair since 2014. Very high quality and easy to use. I have dark brown hair- I mix burgundy and mahogany and the color is gorgeous and I only have to do my roots, once a month. Nobody believes that it’s henna.
"This is my prep:
boil water and shut off before shower
wash hair 2x w/shampoo
wash with 1 cup of apple cider vinegar and let sit for 3 min, rinse out
mix hot water with powders
use application brush from hennahut.com to apply and let sit for 1 hour
rinse till clear
I do not wash my hair for 2 days after. This helps the darker pigment set and my hair oils to further recoup.