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Corporate Hippie
11-21-2005, 01:40 PM
Pressure difference? Whatever that binding property of water is? Hmm?

CalMeacham
11-21-2005, 01:49 PM
Clothes don't stick to you when you're underwater the way they stick to you when you're wet and above water.


You see the same effect with paintbrushes (like those used for watercolors). Dip one in water and the bristles splay out. Pull it out of the water and they stick together.


I've always assumed it was surface tension (which explains why it doesn't work underwater).

WonJohnSoup
11-21-2005, 09:33 PM
I've always assumed it was surface tension (which explains why it doesn't work underwater).

Pretty much. It's actually a result of capillary action, which is related to surface tension.

http://en.wikipedia.org/wiki/Capillary_action

Atleast that's what I understand from G-chem class.

Blake
11-21-2005, 10:23 PM
Pretty much. It's actually a result of capillary action, which is related to surface tension.

http://en.wikipedia.org/wiki/Capillary_action

Atleast that's what I understand from G-chem class.


I can't quite see why how capillary action would make clothes stick to you. Like the link says, cappilary action is the process by which water can be drawn into a narrow space.. Cappilary action helps explain why cloth absorbs water, and can even act as a wick for water. But I can't see any other link between that and clothes sticking to the skin.

It seems pretty obvious that wet clothes stick to the skin for the same reason that wet paper can be stuck to a table, or even to the ceiling: a combination of adhesion and air pressure. Wet clothes are no longer freely permeable to air. As a result when you press them against the skin or any other soild surface you form a somewhat airtight seal. To lift them back up from the middle you need to exert enough pressure to overcome air pressure, which isn't easy. As a result the cloth appears to stick and ihas to be peeled back from the edges. That effect is added to because water is capable of forming bonds with the skin itself, making a kind of very weak glue.

You can experiment with this yourself simply by taking two identical sheets of paper (or cloth) and placing them on a table, and then wetting one. The wet sheet wil become stuck in precisely the same manner as cloth becomes stuck to the skin. But they'll still be relatively easy to lift from the corners. If you want to you can easily stick cloth or paper to the ceiling by wetting it.

I can't see any obvious role here for cappilary actuon beyond aiding in wetting the whole cloth/paper.

WonJohnSoup
11-21-2005, 10:45 PM
I can't quite see why how capillary action would make clothes stick to you. Like the link says, cappilary action is the process by which water can be drawn into a narrow space.. Cappilary action helps explain why cloth absorbs water, and can even act as a wick for water. But I can't see any other link between that and clothes sticking to the skin.

It seems pretty obvious that wet clothes stick to the skin for the same reason that wet paper can be stuck to a table, or even to the ceiling: a combination of adhesion and air pressure. Wet clothes are no longer freely permeable to air. As a result when you press them against the skin or any other soild surface you form a somewhat airtight seal. To lift them back up from the middle you need to exert enough pressure to overcome air pressure, which isn't easy. As a result the cloth appears to stick and ihas to be peeled back from the edges. That effect is added to because water is capable of forming bonds with the skin itself, making a kind of very weak glue.

You can experiment with this yourself simply by taking two identical sheets of paper (or cloth) and placing them on a table, and then wetting one. The wet sheet wil become stuck in precisely the same manner as cloth becomes stuck to the skin. But they'll still be relatively easy to lift from the corners. If you want to you can easily stick cloth or paper to the ceiling by wetting it.

I can't see any obvious role here for cappilary actuon beyond aiding in wetting the whole cloth/paper.

Ah. I was thinking of the water soaking up your clothes and then trying the same on your skin. Your explanation with the air pressure is much better :)