Pour the desired amount of henna powder into the ceramic bowl. Use the spoon to mix it and remove any clumps. Sift the henna powder to make a fine powder if any lumps remain. Add raw sugar to the henna and mix—use a ratio of one part raw sugar to five parts henna powder.
Add lemon juice to the mixture, a small amount at a time, and mix thoroughly. Continue adding lemon juice and stirring until the mixture is the consistency of thin mashed potatoes. Cover the bowl with plastic wrap, and allow it to set until the dye is released. This may take two or more hours, depending on the temperature. At warm temperatures, around 80 degrees, the dye is released faster than at cooler temperatures. The ink is ready when the top of the mixture turns brown and remains green underneath.
Stir the henna mixture, and mix in a drop or two of essential oil, if desired. Adding essential oil will darken the henna and give it a pleasant aroma. Add more essential oil to create a darker color.
Use the henna immediately to create temporary tattoos, or store it refrigerated for a day or two. Store the henna mixture in an airtight and lightproof container in the freezer for up to a month, and thaw before using.
Customize the basic recipe by replacing the raw sugar with brown sugar or honey. Try different sources of sugar to give the mixture a slightly different texture.
Use lavender, cardamom, geranium or tea tree essential oils in place of the eucalyptus oil to create different tints and aromas. Test a small area of skin for allergic reactions or skin sensitivity before using these or any essential oils.
Replace the lemon juice with lime juice, vinegar, grapefruit juice or other acidic liquids. Each liquid reacts differently with the henna, creating a slightly different finished product. Experiment with different combinations until you find your own personal preference.