Why are your hands slippery when dry, get “grippy” when they get a little bit wet, then slippery again if very wet?
In: Physics
If you look at your fingers, you’ll see that there are lots of little ridges. If you lick your finger, you create a little area of dampness on the tip of the finger. When you press it onto a surface, you squeeze water out in exactly the same way as if you were squeezing a sucker onto a pane of glass. You get this attraction of the water locking onto the molecules on the surface of the page and locking onto the ridges on your finger and it gives you a bit more grip.
However, when your hands have a huge puddle on it, what you end up with is a very thick layer of water. You have a layer of water coating your hands, a layer of water coating the other thing you are holding and a layer of water between the two. You end up with a layer of water sandwiched between two other layers of water and that it very slippery.
This is exactly the reason why tires on cars have tread. The tread means that your tire squashes the water out through the tread pattern and stops you getting this slippery sandwich and gives you a better grip on the road. Not enough tread and you slip because the pressure is all distributed evenly, a little water and you get a suction type effect, and too much water and the two objects aren’t actually touching each other and you hydroplane.
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