Will my tan go darker if I sleep with the tan on?
It doesn't matter how much you leave your tan on, there is so much dark a person can go at a time. There are all different products available, some are designed to be left on the skin for long hours, sleep with it on skin, and there are products, called rapid/express, that are designed to be left between 1 and 4 hours depending on how dark you want to achieve.
When I use a product that is designed to be on the skin for up to 4 hours, sleeping with it on won't make you go darker, there is so much it will work, you can leave it on for 2 days (NO YOU CANNOT) that you won't go any darker!
I don't like much when my clients leave the rapid tan for over night mostly because the chances of something going wrong are bigger as you have no control of what you are doing. Like hands between the legs or on the face, you must likely to go to the toilet, and the list goes on.
If it is necessary to sleep with the tan on, go for it. Otherwise wash it in its maximum development timing, usually 4 hours for rapid tans.
If you really need to go darker, you need to book a what we call, double dip, a second session of tan, the next day. This is the case of body builders that needs to go quite dark. And remember one thing, the darker you go the more visible it is when it is fading as your natural colour will contrast with the very dark tan.
Your Personal Tanner