Breaking down lawsonia: What's in Henna
There really is something magical about henna. You apply this dark, wet substance on your skin in pretty patterns, it peels or flakes off, and it looks like you had fun with markers in its place. The magic is in the biology of lawsonia inermis, or the dye within the leaves of the henna plant. Since most people, myself included, do not have access to fresh henna leaves to crush ourselves and make a fabulous paste, dry henna powder substitutes instead with ease. There are a few main aspects of preparing a paste that are consistent across the board, but artists all over the world disagree on what they consider "the perfect recipe."
The primary necessity when turning powder into well-staining paste is an acidic liquid. Most often this is lemon juice, however I've also heard of vinegar being used - although it is odorous, due to its pH it should work just as well. Anyways, the two are combined into a paste and left to sit in a warm corner for hours and hours while we wait for dye release. Basically it's developing. The time varies by how warm the weather is, although an entire 24 hours is fairly standard. The event of dye release is fairly visible, the top layer will be a darker layer of green than the bottom, and the dye will seep through any plastic, visible as an orangey tone.
ALAS! We are still not yet done. Many artists add their own cocktails of essential oils at this point, a few hours before application. Why? They smell good of course! Just kidding! These, and the freshness of the henna harvest, can make aaaall the difference in a beautiful stain. Aromatherapy grade essential oils contain terpenes, organic compounds made within plants. When added to henna paste, the terpenes in the oils yield a darker stain that lasts longer and must be left on the skin for shorter lengths of time. Kerosene also has terpenes, but I would not suggest applying that to your skin.... Everyone has their favorite combination - of not kerosene- including but not limited to: cajeput, lavender, frankincense, eukalyptus, tea tree, ravensara and many more. The addition of these terpene-containing essential oils is called "terping."
But STILL, there are even more variations completely unrelated to terping. Often sugar in some form is added to the paste to alter its consistency. The addition of sugar, honey or molasses makes the paste more flexible and less likely to crack or flake in dried form. Some claim that using tea or coffee strengthens their stains. Some use wine. The list goes on.
I know I've been using the term "dye" to refer to the pigmented molecules in henna, but I want to stress that real henna is completely natural and has no added dyes in it. See my post regarding "black henna."
