We have a great big plastic jar with pretzels in it, and I noticed every time I reached into it, my hand felt cooler. I figured it was ridiculous that the temperature inside the jar should be lower than outside, so why the cool feeling? Moving air makes you feel cooler but I didn’t think the pretzels would really be stirring up a breeze. The only other possibility, it seemed to me, was humidity: If the pretzels were absorbing water from the air, then the humidity of the air would be low, and that would promote evaporation from the skin which would make my hand feel cool.
So I stuck an electronic thermometer / hygrometer in the jar and waited. Care to guess what the humidity reading leveled out at?
“- -%”, which is this device’s way of saying “zero”. Outside the jar at the time, it was about 55%. Yep, it’s dry in there!
It’s the same principle behind the idea of throwing your phone into a bag of rice if it gets wet. Rice dries out air, dry air dries out phone. If you don’t have rice, pretzels would probably work too.