Sanity check: Is water a good thermal insulator?
Last week, we had a few exceptionally cold days that froze a lot of ponds and rivers. On a hike through the forest, I broke through a weak spot in the ice, and soaked my boots with ice-cold water. I rushed to a snow covered spot (because snow is a good thermal insulator) and removed my boots to pour out the water and wring out my socks to get as much cold water out of them before putting them back on.
The socks felt kinda cold at first, but I knew that it wouldn't take long before the cold water in my socks, combined with the freezing temperatures would start freezing off my feet with a lot of pain.
To my surprise, this never happened. After half an hour walking through ice, snow and semi-frozen mud, my socks still felt wet but comfortably warm...?
Later that day I told my dad about this experience. I assumed that it was because my boots were surprisingly well insulated. He said that it was more likely due to the fact that water is a very good insulator. Huh??? Water? A good insulator?? He explained that back in the days, when they had to harvest Brussels' Sprouts in winter (for those of you that don't know: these were/are harvested by hand) they experienced similar effects: when their gloves were new, the plastic outer layer would still be waterproof. 414
Their hands would get very cold when wearing these in freezing temperatures. However, when the gloves were already a little worn down and the outer layer was punctured here and there, water would seep into the inner layer and their hands would be comfortably warm.
This anecdote shocked me... It goes against everything I ever knew about water and its thermal conductivity. I've always considered water a very GOOD thermal conductor, and thus a BAD insulator.
I would be rather quick to reject this theory, but still... I experienced the same thing with my boots?
I also Googled the thermal conductivity of water, and... to my surprise it is indeed rather low? 0.5918 W·m−1·K−1. Somewhere in between Marble and Teflon.
So... is water indeed a good thermal insulator? And if yes, how come I have always known it as a good thermal conductor? If no, how do you explain the effects I experienced in my boots, and the farmers experienced in their winter gloves? 414