The reason, Ventile cotton remains very breathable even when totally saturated in water, is that our sweat molecules are allowed to pass through the very tight weave of the cotton, but water molecules being larger, are restricted.
This is more evident when you have two layers of the cotton working together, the outer layer gets saturated in water, the cotton weave swells up, blocking most of the moisture, then the second inner layer, works as a further waterproofing membrane.
Just about every modern manmade waterproof fabric, becomes almost useless in keeping the wearer dry when soaking wet, Ventile Cotton works in a totally different way to possibly everything sold for the outdoors market, and being seen as very old technology, gets little or no publicity, resulting in virtually nobody knowing of its existence.
You have to be serious about spending possibly close on £400 on a jacket using very old, and in some peoples opinions, totally outdated technology.
Most walkers spending that amount of money, would go for one of the latest high tec modern fabrics, from the top names, and only those needing such clothing for their work would consider Ventile as their chosen material.
Ventile cotton, like all cottons, becomes very heavy when soaking wet, but because of its very fine weave and high quality manufacture, the outside moisture on the cotton does not effect its breathability.
I know that sounds crazy for someone used to a modern waterproof fabric such as GoreTex or similar competitor.
This was the main reason it was developed specifically for airmen during the war, who always risked having to bale out in open water which was usually very cold.
Its the double Layered Ventile that's the most effective at keeping the elements at bay,
Single layered garments are far less effective in heavy rain, allowing moisture through in very heavy rain.
Ventile has been around for such a long time, that it stands to reason most walkers have never heard about it or used it, as its hardly the most fashionable, to be seen in clothing, and with it being compareable in price with the very best clothing on offer, the majority would rather buy the very latest top end jacket, knowing they have a jacket with a proven track record.
Spending large amounts on money, on clothing few people have knowledge or experience in using, does not make sense.
It only makes sense if you know how good the cotton is in everyday use, and have the available cash to take the risk.