Many gases, liquids and solids will diffuse into each other. Imagine a drop of perfume evaporating and the smell spreading through the air. Or dropping salt into water – slowly the salt ions will diffuse throughout it.
This is driven by the random motion of molecules ricocheting off one another with an energy depending on their temperature - the hotter they are, the more they move about. Thus they tend to bounce into spaces where there are fewer molecules to deflect them back again and so the solutions mix. This process takes some time and the difference in concentrations of the solutions is sometimes expressed as a concentration gradient from where the molecules are most dense to where they are less dense.
This process can happen through the cell structures of animals and plants because the cells are permeable to water molecules. This is called osmosis, and is usually driven by a difference in the salt solution rather than temperature.
Osmosis is also said to occur through waterproof breathable hydrophilic membranes when both sides are saturated with condensation and rain. In this case the rate of diffusion depends on the temperature gradient across the membrane and is the same as heat loss. This is really mixing of the condensation and rain, which helps when the rain stops and drying starts.
If the pores of a ptfe membrane aren't protected from salt contamination osmosis can draw water from one side to the other, perhaps sucking rain water in. These microporous membranes are usually hydrophobic (sometimes protected from contamination with a hydrophilic coating). They require the water molecules to evaporate through the pores and condense again on the water on the other side. To do this molecules need the extra energy to break free of the surface tension of the liquid. Again the process is driven by the temperature gradient (which is very small in the cold outer fabric).
As the outer layer in FurTech garments becomes saturated it has a sentiment change from hydrophobic to hydrophilic. This allows diffusion, with very low resistance to transfer of water molecules from inside to outside through the relatively large voids in the fabric. This effect is tiny but is also augmented by surplus water draining from the hem of the garment, being shaken off by the fabrics movement in the wind or being picked up by water running over the surface.
The latter may be a much bigger contributor to removing moisture from the system than osmosis. Water likes to stick to water. It has a molecular attraction that is observed as surface tension and you can witness this attraction by watching a rain drop run down a window: it tends to follow a tortuous path as it sucks up other droplets. The same is true when you watch rain run over a water repellent fabric. In fact, big rain drops can leave a dry patch around them where other drops have been sucked in.
The outer fabric on FurTech garments, once saturated in prolonged wet weather, sucks water off the inner fur fabric which remains water repellent. Once the outer gets saturated it can't get any wetter and the surplus drains away.
On the other hand membrane garments are typically worn over wicking (hydrophilic) base layers. These layers suck condensation back towards the body. So you get wet from condensation in them, whether osmosis occurs or not.
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