This is the greatest material ever invented. Gore-Tex keeps you dry, period. I've stood under a waterfall in a Gore-Tex parka and Gore-tex pants and not gotten more than a few splashes on me.

How it works:
Gore-Tex consists of a two or three-layered membrane. This membrane has holes several thousand times the size of a water molecule (to let humidity out for comfort and breathability) but much smaller than the smallest possible droplet of water (to keep water out for dryness). Gore-Tex kicks ass. I just wish it wasn't so frickin' expensive

There are also a variety of Gore and Tex related textiles.

Gore-Loft (something to do with sleeping bags), Todd-Tex, and just plain Gore.

Gore-Tex is yet another corporate American myth, much like Harley Davidson and the Leatherman Tool; the product is for some reason seen as better than it is because of rumours, glorification of history and possibly planting of memories. For instance:

I've stood under a waterfall in a Gore-Tex parka and Gore-Tex pants and not gotten more than a few splashes on me.
Not getting wet under a waterfall is easily accomplished by wearing a plastic bag. Any $4.99 rain gear will keep you dry under a waterfall. This is not what Gore-Tex is about.

Gore-Tex is one of many fabrics that use reverse osmosis in order to transport water vapor off your body. You only need this when wearing garments that don't breath naturally, such as plastic, as opposed to cotton. When putting on plastic garments for water protection, the ability to transport humidity from beneath the garments is impaired. Enter Gore-Tex: By using a membrane that will allow water vapor but not water molecules to pass, it makes possible physical activities in rainy weather. It is not better rain gear and it will only keep you dryer from the inside, not from the outside, compared to a plastic bag. 

Gore-Tex will not work if

  • The garment is wet - diffusion won't work. This is why you have to keep on applying expensive water-repellant over and over again
  • The garment is dirty - diffusion won't work. This is why you have to clean the garment, and then have to apply water-repellant .
  • It is cold outside - diffusion won't work. If the water cannot create drops of water on the outside of the garment, the water will not pass through the membrane. 
  • The garment is flexed - diffusion may work in opposite direction. 
  • You did not register your Gore-Tex product with the W L Gore company.  (j/k)

The function of the membrane is heavily dependent on how clean the fabric is and that it is treated with some kind of water-repellant.  If the water-repellant cannot stop the garment from getting wet, and  your Gore-Tex garment is soaked from the rain, the Gore-Tex will get get you soaked. Sit down on a stone in a wet Gore-Tex pant and your underwear will get all wet. The membrane works in both directions, and when the garment is wet, it will not transport water vapor from your body. The same goes for Gore-Tex in shoes, where the W L Gore company will not guarantee the same kind of waterproofness as for other products. This is because the constant flexing of the membrane will work water in the opposite direction, in some conditions. It is also important that there is air between your body and the Gore-Tex membrane. If not, the diffusion will not work.

Other manufacturers have their own fabrics with the same function and properties, for instance Sympatex, Membrane and MPC. Gore-Tex is by far the most expensive, which has got to do with their extensive warranty. The truth about registering your garment is that the waterproof guarantee is only valid for the initial buyer of the garment. W L Gore Co. were also the ones who invented the distinction with "degrees of waterproof-ness", and that says about all about Gore-Tex for me...

What bigmouth said. I have a Gore-Tex rain shell that has been virtually useless from day one.

However, if the Gore-Tex layer is protected by an outer layer to keep it clean and dry, the combination can work quite well. I have a pair of hunting gloves by Gates which I use on my motorcycle in the winter. These gloves have a soft inner layer, then Thinsulate for warmth, then the Gore-Tex, and finally an outer layer of tough camo something-or-other (not nylon, because it's silent when brushed). These are the only things I have found that will keep my hands dry, and thus warm, in a sleeting rain with a 75 mph wind chill. I even have a pair of neoprene diving gloves which do a great job in warm wet conditions, but they just can't hold the heat against that kind of convection. I haven't taken the gloves apart to find out why, but the inside stays dry even if the outer layer is soaked through, even when doing things (like working the clutch) that might bring the Gore-Tex in contact with the wet layer and cause osmosis.

A water proof membrane made by Gore. The membrane is made of micro pores and works on the principle that water droplets are larger than air molecules (yeah, I know air is a mix of oxygen, nitrogen and other stuff, but we'll call it an air molecule!). The pores are large enough to let air pass, but too small to let water through. Therefore water droplets cannot pass through the membrane, whereas air molecules and vapour can. We say that the membrane breathes.

The Gore Tex membrane is laminated onto an outer shell, usually some sort of polyester fabric, which is heavily impregnated.

The membrane is made from the same material as teflon, and withstands extreme temperatures.

There exists three different types of Gore Tex shells:

  • 2-ply: in a 2-ply shell, the membrane is laminated onto an outer shell, and an inner mesh hangs loose to protect the mebrane, which is otherwise unprotected.
  • 3-ply: in a 3-ply shell, the membrane is laminated onto an outer shell and an inner protective lining. If the inner lining gets moist (ie. from sweat), it can freeze, this is usually only a problem when you're high up in the mountains.
  • PacLite: the membrane is laminated onto an outer shell, and small rubber pads are glued directly onto the membrane to protect it.

The 2-ply construction makes for a soft, quite silent, shell, often used in skiing clothes. 2-ply clothes do not withstand the severe abuse of a heavy backpack as the membrane will be rubbed between the inner mesh and your back.

The 3-ply construction resits much harder use as the 3-ply shell is laminated together into one sheet. This makes it a bit thicker and slightly heavier, and it doesn't breathe as good as a 2-ply. Still, a 3-ply shell is the most allround Gore Tex shell you can find.

The PacLite is very light and packable and also the most breathable. It's a very good choice for hiking, although the rubber pads will be worn out after a while. The membrane is also exposed (as in the 2-ply), so it will not endure the same hard use / abuse as a 3-ply shell.

In the winter 2000, Gore released a new membrane -- Gore Tex XCR, the Extended Comfort Range membrane. This is made as a normal 3-ply shell, but the membrane breathes about 25 - 40% more than a normal 3-ply. To put it another way, the XCR breathes almost as good as a 2-ply or a PacLite shell, making it a very good choice for heavy daily use.

See also: Conduit, Dermizax.

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