Use a seal like lemon and sugar. Apply this before the paste dries completely and apply this periodically until the paste congeals. You can pop some tissue paper over this and a sock. This will keep your henna nice and warm and help the dye release.
You can also seal with medical tape. Both methods keep the paste in place, moist and warm but we have found that together they can make the design bleed.
Keep the paste on as long as possible, at least 4 hours, overnight if possible and avoid water for 12 hours.
Also avoid vaseline or any petroleum based cream as this will diminish the design. We use a coconut based moisturiser or olive oil to moisturise or protect in the shower.
Keep warm! Drink tea, use a hair dryer or best of all, get your Henna design out in the sunshine, this is the best method of all!