Photo: Comstock/Comstock/Getty Images
Women have been using henna to dye their hair for thousands of years. In modern times, many women have been saying "nay" to the ammonia and para-phenylenediamine (PPD) in many chemical dyes, and "yay" to natural, organic henna blends. Henna works by bonding color to the proteins in your hair. Unlike chemical dyes, it does not strip the melanin of its color -- which means that you can only go darker, not lighter. So if you want to go platinum blonde, henna just isn't for you. Otherwise, with a careful mix of henna with other natural substances such as indigo and lemon juice, you can create a wide variety of colors, from a sunny strawberry red to a deep black.
The more lemon juice you mix into your henna, the more golden the results. With a high-quality henna powder plus practice and care, you can achieve a natural-looking red hair color such as a deep strawberry blonde or fiery orange. Or you might go for a more exotic, bright and artificial color such as fire-engine red, copper or burgundy.
If you mix your henna solution with an indigo solution, the result will be brown hair. Indigo is a different species from the henna plant, but most vendors of henna also sell powdered indigo. Instead of lemon juice, use apple cider vinegar. Also try adding some powdered amla, which helps your dye result in a color that is more brown and less red. With the addition of indigo, your hair could come out light brown, dark brown, or mahogany -- a dark brown with a hint of red. Beware, though: if you are going for a light brown color, re-dyeing your hair with the same formula will result in darker and darker browns, since the dye is building up on your hair.
Dyeing your hair black using henna is a two-step process. First, you have to dye your hair red with a henna mix. Then, use a separate indigo mix to result in a jet black. If you don't use the henna first, your hair will turn an ashy grey color, so don't skip the first step!
How to Get the Color You Want
Since henna is a natural substance that can spoil or grow differently in different fields, it is easy to end up with a hair disaster if you aren't careful. First of all, purchase your henna from a reputable dealer who sells body-art-quality henna. The dealer should distinguish between different batches of henna -- some batches are stronger than others -- and store the henna in airtight packages. Ask lots of questions and follow the instructions exactly. Once you dye your hair, it might look green or dark blue for 24 to 48 hours before going to the color you want, so don't panic or rush out to your salon to correct it.