If red stains are desired on hands damaged by chemical relaxers or that are regularly oiled, leave henna in place overnight and steam or heat the hennaed skin repeatedly while the paste is in place. This will make a more even and richer colored stain.

For darker palm stains on damaged or oiled skin, clean the skin with rubbing alcohol before applying henna. Include in the henna paste an essential oil with high levels of terpines such as pinene, limonene, or nerol, which react with the henna dye molecule to darken stains . This creates a darker henna colors on difficult skin. Thus adding Neroli essential oil, having moderate levels of these terpines, darkens henna to a warm brown. Neroli essential oil has a bitter orange fragrance, and is derived from Citrus aurantium.

Darker brown stains can be achieved on damaged and oiled skin by adding essential oils with high levels terpineol, terpinene-4-ol, eugenol, geraniol, linalol, and cineol, to the henna paste. These react particularly well with hennotannic acid, creating a quick dark stain in epidermal cells. Tea Tree, ravensara, cajeput, cardamom and geranium essential oils have high levels of these terpines, and are unlikely to cause any skin irritation. High quality pure essential oils are costly, but will do a superior job to those diluted with filler oils.

Dry Heat, Moist Heat and Sweat:

The safest, cheapest and most efficient darkeners for henna, and the most widely used in equatorial countries, are heat and sweat. If you apply henna in a humid climate at 100°F (37°C)and above, the henna will stain quickly and intensely, often staining burgundy-black simply from the heat. Many henna artists dry their client's henna over smoky coal fires, as the heat intensifies the henna color. Heat also encourages perspiration, containing ammonia, which darkens henna to near black. Steaming the hennaed skin intensifies the stain. A whistling teakettle, a pan of simmering water, or a garment steamer can be used to heat and rehydrate henna paste on skin. If hennaed skin is steamed repeatedly over a period of hours, the resulting stain will be dark. Saunas, hot days, campfires and steam are safe and effective ways to darken henna.

For more information on techniques of darkening henna, see: How to mix henna, and the Ammonia trick.