Solder wick is basically just braided copper wire that absorbs molten tin solder in contact. But how does it work? The molten solder is very effectively sucked into the braids. The same effect is not achieved by just one thick strand of wire. I'm thinking there is some kind of capillary effect happening, but further than that I cannot say. The molten solder, instead of melting, is sucked into the braids; why doesn't it just flow everywhere instead of flowing along the wires that make the braid?
I think this is more of a physics question than electrical engineering question as it does not involve electricity or electronics directly, so I'm asking this here.