Why are your hands slippery when dry, get “grippy” when they get a little bit wet, then slippery again if very wet?
In: Physics
Others have explained the sources of this effect: (1) you skin swells and (2) surface tension.
I wanted to add that this is very similar to a story I once read about Albert Einstein musing about beach sand. He noted that it is hard to walk in totally dry sand and also hard to walk in sand that is submerged in water, but easy to walk on sand that is wet but not submerged, right where the waves stop moving up the beach. He then explained his own observation: sand that is wet but not submerged in water sticks together through surface tension.
So this question has an excellent pedigree. I did some googling to find the story and I think this is it, but it is behind a paywall:
[https://physicstoday.scitation.org/doi/full/10.1063/1.2169417](https://physicstoday.scitation.org/doi/full/10.1063/1.2169417)
Is this even true? Is the point of chalk for climbers etc not to dry their hands to increase grip?
TIL this sub does not explain like I’m 5 anymore. There are a lot of correct answers upvoted most, but none at the top fit the intention of the sub lol.
When dry, all the “grippiness”, or rather friction, between your hand is skin on the surface’s object.
When just slightly wet, the moisture fills in the tiny gaps between your skin and the object. It basically acts like a weak adhesive.
When your hands are very wet, there is so much water between your skin and the object that it nor just fills in the small gaps mentioned above, but forms a film between your skin and the object, thus greatly reducing grip.
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