When we go to bed at home, we started to put a bowl of water on the radiator (the air gets a bit dry).
By instinct I put a soaked piece of paper (e.g. toilet paper) into the bowl and let it touch the radiator. The next morning all the water in the bowl was gone. My wife was not so sure that the paper actually had any effect. So I put two bowls of water.. one with the paper and one without. The next morning the bowl without the paper had all the water remaining and the ball with the paper was empty and the paper completely dry.
paper _____ / | \ -----/---/ | \ ------ / \ \------/ \__ ------------------------- radiator
What is the physical mechanism for this "paper pump"? By how much does the temperature difference between the water and the radiator overcome the gravity force?