Any idea on why Gore-tex boots gets wet in snow but not under running water?

[Tianming C]

I got a pair of Salomon X Ultra 3 Mid GTX last November. I have used them in rain, stepping into puddles and stream and never had problems. Recently I took a walk in snow for a few hours and found the inside of the toe boxes to be wet. Later, after the boots dried up, I push them under a running tap to test if there’s a leaking point. To my surprise, after 1 minute of continuous downpour from the tap, the inside of the boots didn’t get wet at all. I even tried summering the front of the boots, but still doesn’t get any leak. I’m now confused about how them got wet in the snow. Is it something related to colder temperature? It wasn’t very cold though, just about 30F. Or could be the salt used to melt snow? (I was walking in the city.) Any ideas? Thanks in advance!

[Roger Caffin]

The answer is very, very simple.

When you are walking through the snow the surface of the boots will be below freezing. Under these conditions, some of the sweat from your feet – and your feet DO sweat, will condense inside the boot. It can’t get out, and it will collect there. Goretex linings almost always do this, and lead to the well-known ‘prune feet’.

Cheers

[Tianming C]

My socks were dry though. It was only the front part of boots that felt wet.

[Roger Caffin]

Most likely the warmth of your feet pushed most of the moisture out of the socks onto the much colder boot material.
This is not a new discovery.

Cheers

[Tianming C]

That makes sense. Thanks for the explanation! Glad to know my boots aren’t defective.

[Dan @ Durston Gear]

GoreTex allows humidity (water vapor) to pass through it but not liquid water. This humidity always moves from areas with higher humidity to lower humidity. It’s not always going to move out – it can move in.

So if you were to toss on dry socks and have perfectly non-sweaty feet, if you go out and stand in slush for a couple hours (100% humidity) eventually you’d get 100% humidity inside your boots too. In this case you were out in the snow with temps around freezing. The outsides of your boots were likely soaked (100% humidity) so the outside air has no ability to accept moisture and thus your boots aren’t going to breath. So if your feet were dry eventually they’d become damp, plus since the outside is soaked the sweat from your feet can’t get out because (1) it will condense into liquid water when it hits the cold boot as Roger said, and (2) even if it didn’t, the 100% humidity outside would likely result in no breathing happening since it has no capacity to accept moisture..

The major problem with GoreTex (or other WP/B) footware is that in conditions where you might want it, it is typically wet enough outside that your boots are soaked on the outside so breathing isn’t going to happen. This is why they also apply water repellant coatings on the outside (so the outer layers don’t get 100% soaked) but in wet conditions this doesn’t last very long. You may as well save a few hundred bucks and just use plastic bags. At least then you can remove the bags and have breathable footware in dryer conditions.

[Matt Dirksen]

Do you mean your toes were wet behind this area? Goretex or otherwise, no vapor is pushing through that rubber toe piece. If this is the only part of your boot that you are having condensation issues, then it’s clear to me that “something” is working. Or else your whole sock would be wet from condensation.

Toes are also not the “warmest” part of your foot, so there’s not as much localized heat to “drive” the vapor through the membrane, either. But no matter what, the rubber will keep water out, and vapor in.

Just to be clear: assuming no leaking has occurred, any wetness you experience is from you, not from the environment out there. As Dan said, a fully surface saturated boot won’t let vapor out either, so the vapor from your feet will quickly condense into bulk water once your socks are saturated.

Vapor only moves from warm to cool, and from a more humid environment to a drier environment. While theoretically possible, the ONLY way for vapor to drive into your boot is if it’s both dry AND COOL inside. So – perhaps a very hot humid day and you have an air conditioning system cooling your feet?

Time to wear sandals.

[Tianming C]

You are right. Even though inside the boots underneath the mesh (right to the red arrow) was wet, my socks weren’t soaked. The only part of my socks that got wet enough that my feet felt it was the toe part.

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