Mixing the Henna
Pour your desired amount of henna into a plastic container. Shorter hair usually takes 3.5 oz. of henna or less, whereas longer hair might take up to 10.5 oz.
Cut the lemons or oranges in half. Squeeze the juice of each into the henna. Stir the henna and citrus juice until all the henna powder is coated.
Pour in enough spring water to form a paste-like consistency. Stir the mixture with a spoon. If it becomes too watery, add a bit more henna to the mix.
Place the lid on the plastic container. Put it in the refrigerator for at least 12 hours.
Dyeing Your Hair
Slather your forehead, neck and ears with petroleum jelly. Henna really stains the skin, and the jelly protects your skin from the color. Place a towel around your shoulders to protect your clothing.
Put on your gloves. Scoop up some of the henna mixture and run it through your hair. Repeat until you've used up all the henna and thoroughly coated all of your hair. Pile your hair on top of your head and put on a shower cap.
Keep the henna on as long as possible. For covering grays, try to keep it on overnight if possible, as not leaving it on long enough can make your gray hairs turn orange. Anywhere from eight to 12 hours is ideal.
Rinse the henna out. After wetting the hair, add a little conditioner to your hands and use it to break apart the dried henna. It can be a little tough to scrape everything off. You'll know you've successfully washed all the henna out when the rinse water runs clear.
Step out of the shower and dab your hair with a towel. Apply a leave-in conditioning treatment. Allow your hair to air-dry.
Henna darkens over a few days, so don't fret if the color isn't exactly what you were hoping for right after you dye it.
If you're going to dye your hair overnight, place a towel on your pillow so the henna won't leak onto your bed.