I have been using the 20% nouvatan as a rapid tan and had some really good results with it but it really depends on the persons skin type to how quick the show colour. I sprayed one girl who washed off after 3 hours and looked like she had a 10% and then another girl washed off after 3 hours and looked only slightly darker. but she developed darker over the next few hours ? its like the skin always absorbs the dha. but on some people they brown up quicker than others do.
I left it on overnight and i was dark brown my mate who is light skinned looked like she had had a 12% it faded great on me and lasted about 9 days . but it only lasted about 4 days her.
I have started telling some really pale people that there skin wont take a 20% if its left on overnight and that it will make me look bad if the results turn out bad. because they insisted on leaving something on that i as a trained therapist have advised them to wash off after 3 or max 4 hours
all in all though i love the 20% and have just ordered another 3 litres as it works out cheaper if you buy it in 3s