Before use, mix 1 tbsp of indigo powder and 1 tbsp of lemon juice into the henna paste. Coat your hair evenly, leave the pack for 2–3 hours, then rinse thoroughly with plain water. Avoid shampooing ...

“It doesn’t need to be freshly shampooed, but it should be free of any buildup of oils, dirt, or styling products that might prevent the henna from adhering properly to the hair shaft.