Re:
Wise words from the auld fella
old_coyote_pedaller":1q75h884 said:I read an article in a climbing/mountaineering magazine I use to get many years ago about Goretex and how breathable it is.
In ideal conditions, i.e. not in normal use the way everybody actually uses Goretex jackets, it is perfectly breathable but ideal conditions almost means laboratory conditions. Goretex needs vapour pressure to push out the moisture as vapour molecules which are small enough to pass through the pores in the Goretex membrane. To maintain this vapour pressure it has to be warm enough inside jacket so that it does not condense into water which cannot pass through the pores as the water molecules are too big. This is also how Goretex stops rain getting in.
Jackets need to be almost sealed to create the warm atmosphere which will maintain this vapour pressure. If, as we all do, wear a jacket with zip down a bit or sleeve cuffs open because we are too warm, or hem of jacket is open which most are normally, we allow the interior of jacket to cool down so there is no vapour pressure. Damp/wet patches then occur.
If there then is a layer of actual moisture on inside of jacket it cannot pass through and the water vapour cannot either.
That is also why jackets have to be cleaned and occasionally re-proofed so that rain balls up and runs off the outer fabric, if it gets wet the vapour cannot pass through it after passing through the pores in Goretex. Probably the inner fabric also needs to be clean and proofed as well for same reasons.
Some of the above may be me misremembering but it is essentially why most folk moan about their "waterproof" :roll: jackets.
Wise words from the auld fella