Leave paste on as long as possible
The longer the henna paste is on the skin the darker the stain will become. 2 hours ok. 4-6 hrs good. Overnight superhero! (Beware white sheets, henna can restain even when the paste is dry.)
Hot, hot, hot!
In sunny Queensland, Australia we have great weather for henna. The warmer the skin the darker the henna will stain. So keep warm and wrap up in winter.
A little extra thing you can do to really push your henna colour deeper is to wrap the area with medical tape, bandage or even an old sock (cut out the toes for hands or arms.) I like to use an old bandage over larger areas.
Removing the paste
Do not wash paste off! Peel off the paste. If there are any stubborn bits use oil (olive oil will do fine). Try to keep dyed area dry until the next day. Wetting the area will create a lighter stain. Living on the Sunshine Coast means I often swim to soon, I still get a nice colour with good quality henna but definitely avoid areas that don’t stain well if you really must swim. Stick with hands and feet. Feet are good for staining quickly.