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Not having a pair of lightweight rain pants, I decided to put on OR Mentor Goretex pants to commute by bicycle in the rain. When I got to work about 15 minutes later I had a big wet spot on each knee. I don't think it was sweat, because everywhere else was dry. If the water repellent coating wears off does the Goretex lose it's waterproofness? For the price of these pants, and their intended use, I would have hoped they could keep me dry for 15 minutes in the rain.

Here's why GoreTex sucks: the water has to get TO the membrane, past a less-breathable urethane or fabric protective layer, and then has to get FROM the membrane out of the garment. If the outside of your garment is wet, then there's a water barrier that will prevent moisture leaving. The US Army did a bunch of tests: you can see the graphs online (though they predated the new kinds of GoreTex that try to compete with eVent). Do I use PTFE garments? Yes. But I recognize that the "Guaranteed to Keep You Dry" promise only applies if it's not raining For that reason, I try to avoid hyped-up GoreTex-brand membranes, since they cost extra and have the same achilles heel as all the others. eVent works best in my experience.

To my knowledge Gore-Tex isn't really waterproof, just fairly water repellant. If you want waterproof buy a rain suit.

The outside layer is not waterproof, so will eventually get wet. At that point the cloth drops to the wet bulb temperature, and moisture on the other side (say from sweat) will condense.

Membranes like gore-tex are indeed waterproof.

http://www.backcountry.com/store/newsle ... ained.html

Most gore-tex clothing uses a layer of gore-tex underneath some outer fabric; I'm not at all surprised if that outer fabric becomes less water-repellent over time, especially at the knees where it is subject to lots of wear.

If you were biking in the rain, you did sweat, and most of the evaporated sweat condensed on the inside of your pants (cooled by the outside air, rain, and a bit of evaporative cooling), because the outside humidity was too high for most of the vapor to escape through the membrane. This is especially so at the knees where the mebrane was in direct contact with the cool, soaked outer layer. Also, your knees would stay sweaty (less evaporation inside the pants) because your skin at the knees would be in contact with the pants much of the time.

So most of what you saw on the outside of the knees was rain, but most of what you felt on the inside of the knees was probably sweat.

It's always possible somebody sold you a fake fabric (not really Gore-Tex), but this doesn't prove it.

GoreTex definitely has a finite lifespan. This photo shows an example, that cannot be explained by sweat or condensation.

"Waterproof" is not meant to be taken literally. There is no such thing as a completely waterproof fabric. Even ships leak, that's why they have pumps.

Gore-Tex works because there's a plastic membrane layered between two pieces of plastic fabric. That membrane is designed to allow air molecules through, while resisting water molecules. But it doesn't do either one all that well: It doesn't breathe all as well as an untreated cotton or nylon taffeta, and it doesn't resist water as well as a trash bag-- it's an imperfect and rather expensive compromise.

If you're working hard and sweating, the sweat will condense and drip back on you-- if you're outside in hard rain, the fabric will eventually saturate and the rain will come through. In your case, you got to enjoy the best of both worlds.

If you play in the rain, you're going to get wet. You want something that does a better job og keeping the rain off you, while letting your sweat evaporate, then buy an umbrella.

It's a mean old world.

jdzaharia wrote:GoreTex definitely has a finite lifespan. This photo shows an example, that cannot be explained by sweat or condensation.

Yes but it can be explained by them getting scared

nartreb wrote:This is especially so at the knees where the mebrane was in direct contact with the cool, soaked outer layer. Also, your knees would stay sweaty (less evaporation inside the pants) because your skin at the knees would be in contact with the pants much of the time.

Funny, I've never seen my knees sweat when I was working hard. Probably couldn't see from all the sweat running in to my eyes from my forehead.

Forgot to mention that Gore Tex has a Keep You Dry Guarantee so if you're not satisfied with a Gore Tex product send it back to them.

http://www.gore-tex.com/remote/Satellit ... ep-you-dry

I have had great results with goretex even in very heavy tropical rains. I did have a goretex jacket that turned to junk (lost waterproofness) but that was after 10 years of use.

DanTheMan wrote:Not having a pair of lightweight rain pants, I decided to put on OR Mentor Goretex pants to commute by bicycle in the rain. When I got to work about 15 minutes later I had a big wet spot on each knee. I don't think it was sweat, because everywhere else was dry. If the water repellent coating wears off does the Goretex lose it's waterproofness? For the price of these pants, and their intended use, I would have hoped they could keep me dry for 15 minutes in the rain.

What if you use your pants when mountaineering instead of cycling

http://www.outdoorresearch.com/site/m_s ... pants.html

http://www.gore-tex.com/remote/Satellit ... /pro-shell

Here is an article with a link to the US Army study that Elliot is referencing.

http://www.getoutdoors.com/goblog/index.php?/archives/1516-eVent-versus-Goretex-Pro-Shell-The-Battle-Lines-Are-Drawn.html

DanTheMan wrote:Not having a pair of lightweight rain pants, I decided to put on OR Mentor Goretex pants to commute by bicycle in the rain. When I got to work about 15 minutes later I had a big wet spot on each knee. I don't think it was sweat, because everywhere else was dry. If the water repellent coating wears off does the Goretex lose it's waterproofness? For the price of these pants, and their intended use, I would have hoped they could keep me dry for 15 minutes in the rain.

It's not that the gore-tex has lost it's waterproofness or isn't breathable. My assumption is that you didn't open the side zips at the thigh on the mentor pants in order to vent while doing a high aerobic activity. If that's the case, it wouldn't matter what you were wearing (even eVent), it would feel wet from interior condensation (Paclite does this more so than ProShell because of the slicker inner surface, especially over bare skin) because you are simply overpowering the ability of the material to move moisture. It may seem ridiculous to open the side zips because then water can obviously come in, but it really just depends on your physiology on how much they need to be opened; even a little bit (like 4") can make a difference without letting much water in. At this point it is more a matter or staying comfortable than staying 100% dry.

Another question is have your pants been washed recently, or seen a lot of use since their last cleaning? If not, or they have seen a lot of use, I would suggest washing them and then seeing if that helped. Dirty gore-tex, especially from body oils and grime, is seriously hindered in its performance to move moisture. And putting in the drying on high will reactivate the DWR in case that has lost it's abilities as well.

And as mentioned above, if you have concerns about your product, call 1-800-GORE-TEX. You will talk to one of three people (they actually don't get as many calls as people may think) and they will be more than happy to discuss the issue with you.

GoreTex is a necessary evil. Seeing how it's next to impossible to find waterproof footwear without it, it does have some redeemable value. I did some product testing for GoreTex a few years ago on a NOLS course in Alaska. It is my opinion that the fabric reaches a sort of saturation point. Up to a point, it is waterproof and amazing, but after say, five days of constant rain, it's about as useful as a windbreaker. I'm saving up for an Event Jacket myself.