[This is the first-ever article published in a consumer magazine which questioned the efficacy of Gore-Tex material and the veracity of its many, many exaggerated and misleading claims.]    

SUMMIT/ May-June. 1984

Gore-Tex^® Clothing: Is it any good ?

An Atlantic Alpine Club Report Copyright 1984 by Tom Holzel

Gore-Tex® is a proprietary clothing material, invented and marketed brilliantly by Wilbert L. Gore & Associates, that has taken the outdoor sportswear market by storm. Seeming to promise a "one-way mirror" effect with moisture, this cellophane-like material is bonded to conventional fabrics and promises to keep rain and cold out, yet allow sweat to pass through to the outside and so keep an exercising user dry.

Advertisements collected from a single issue of a running magazine features products touting Gore-Tex fabric that makes the following claims:

• A running suit that'll keep you warm and dry even in the coldest, soggiest, most miserable conditions.

• No matter how much sweat or rain you come up against, the suit will keep you dry.

•  It's ideal for three season wear. . .

•  Dry inside when it's wet outside. A shoe that repels water, yet allows fresh air in.

At first glance these advertising claims seem too good to be true, but the explanation given for how Gore-Tex is supposed to work does sound logical. Gore-Tex runs  generic ads  which  give  the  "in­side story":

The Gore-Tex membrane has 9 billion pores per square inch.(!) Water can't get through pores that small. Wind can't snake through. But per­spiration can get out. Because you don't sweat drops: you sweat vapor.

And, the ad explains, water vapor molecules are 700 times smaller than Gore-Tex pores, while water droplets are 20,000 times bigger. It sure seems to make sense, but does it?

Early first-generation Gore-Tex fabric actually did have microscopic holes large enough to permit air to diffuse through. This was handy because in­side the jacket, air warmed by exercise and sweat vapor could escape and so help to keep the athlete cool and dry.

However, early Gore-Tex proved unsatisfactory because it slowly became "poisoned" by oils con­tained in sweat vapor. This caused the fabric to lose its waterproof capabilities. Until recently the problem of waterproofing the garment's seams was also not solved satisfactorily, and to find a one-year old Gore-Tex jacket that was still truly water­proof was a rarity.

The sweat poisoning problem is said to have been cured by the second generation Gore-Tex material. It is now a permeable film that passes water vapor by osmosis rather than sieving it through carefully sized holes. New Gore-Tex will not pass air; you could make a balloon out of it. How then can the Company claim that it "breathes"?

The dictionary defines breathing as "to inhale and exhale air," i.e. the circulation of air, not the movement of vapor. Manufacturers of Gore-Tex running suits tacitly acknowledge this lack of breathability by placing large ventilation slots in their clothing-—either under the arms or across the entire back. Even so, anyone who has built up a good sweat in a Gore-Tex suit has soon discovered-—by getting soaking wet from the inside—-that Gore-Tex "breathability" certainly cannot mean the same thing as ventilation or the movement of air. Yet thousands of outdoor sport aficionados swear to Gore-Tex's effectiveness. Can they all be wrong?

A look at what actually happens to the "micro­climate" surrounding an athlete is instructive. When exercising, metabolic combustion creates heat that, if it is high enough, raises the body's temperature above its optimum level. An over-temperature reflex causes the body to exude sweat in the form of liquid (600 gm/hr) and vapor (60 gm/hr). The sweat is at body temperature, so its excretion to the outside is itself a means of reduc­ing the body's heat load. Still, it is the evaporation of liquid sweat that absorbs the largest amount of heat.

The problem with Gore-Tex in warm weather is precisely that the quantity of sweat vapor it can pass is extremely limited. Without true breathability, the heat and then the humidity inside the suit rises quickly to the saturation point, turning sweat vapor into wet, liquid sweat at the Gore-Tex bar­rier. One solution is to ventilate the suit with large slots to permit the escape of the moisture laden air, and its replacement with drier air. But even this stop-gap measure is of limited effectiveness when it is not raining, and self-defeating when it is.

In colder weather the heat load will tend not to build as rapidly with conduction playing a greater role in reducing the temperatures inside the suit. In such climes an athlete will be wearing some form of underclothing which will ordinarily absorb some of his sweat, both as liquid and as vapor. This is undesirable because it means the underclothing traps the very heat load the body is try­ing to rid itself of. Worse yet, after the exercise is over, evaporation of damp underclothing may cause over-cooling of a fatigued athlete, already cold from cessation of activity.

One successful attack on the problem of cold, damp underwear is to attempt to preserve sweat in its vapor phase by avoiding underwear that ab­sorbs water vapor (which is not the same as ab­sorbing liquid water). Synthetic garments such as knitted polypropylene, acrylic or polyester absorb less than 1% of their weight in water vapor, while cotton absorbs 6% and wool 15% of water vapor. By maintaining sweat as a vapor, it can move through the underwear without giving up its heat or turning to liquid, and so reach the Gore-Tex layer and be carried through it to the outside.

Of course, there must be sufficient energy (in the form of heat) along this entire route—from skin to outside—to maintain the water in its vapor phase and to propel the water vapor in the right direction, transversely through the dense Gore-Tex maze. For this reason, the Gore-Tex layer should always be kept at as high a temperature as pos­sible, that is, close to the heat source, the skin. It is here that the clothing system concept of "wicking" comes into play.

Dr. Brian Farnworth of the Canadian Defense Research Establishment Ottawa has been study­ing the propagation of water vapor and heat through fabric. He maintains that the second most erroneous claim made by sportswear advertisers (besides the run-in-the-rain-and-stay-dry variety) is the entire concept of moisture "wicking."

Wicking, the advertisers of synthetic underwear and socks will have you believe, transports liquid sweat out from your skin transversely through the synthetic layer of clothing to the next layer of clothing.

• "Since  polypropylene  cannot  absorb  moisture, perspiration is passed through to the outside so you stay dry and comfortable."  (REI  "Lifa"® polypropylene products)
•  "Olefin yarns wick moisture away from skin to outer socks,  feet stay warm and dry."   (EMS Olefin liner socks)

To test this interesting claim, you need merely dunk a polypropylene undershirt into a tub of water to discover a not very amazing fact: knitted polypropylene picks up an enormous amount of water-—perhaps ten times its weight or more. True, this water is not absorbed by the fibers, but it is held mechanically in the space between the fibers by capillary action. If anything, this capil­lary action resists tenaciously the transverse movement of liquids.

However (there always seems to be an however), synthetic fabrics yarns will "wick" liquid sweat longitudinally, i.e., they will spread out a small spot of water within the same fabric layer (from under the armpits, say) and thus provide a greater surface area from which it may evaporate. This can result in a significant advantage because—-especi­ally in the case of Gore-Tex—-the larger the sur­face area, the more effectively a given amount of water can be exposed to hot skin, turned back into vapor, and transpired through the Gore-Tex fabric.

In winter clothing, the insulation layer places the Gore-Tex so far from the skin that nearly all sweat will have been cooled to a liquid state, or even to frost. This cooling occurs inside the gar­ment which then becomes a reservoir of sweat-frost during the day, and damp liquid sweat if brought into the sleeping bag at night. Even under the thinnest clothing systems with Gore-Tex as the outer layer, very little vapor will pass through the Gore-Tex in below-freezing weather because of the low saturation vapor pressure of the cold air. In other words, cold, outside air has almost no capac­ity to pick up water vapor from the Gore-Tex layer.

If Gore-Tex does not work fast enough to be noticeable when exercising in warm weather, and barely works at all in the cold, is there any use for it? Yes, indeed, and in markets far larger than heretofore seen. But like the ill-fated "breathable" Corfam ®, imitation leather once manufactured by DuPont that also did not seem to breathe, market­ing types always want to position their products at the top. There lies the least price resistance (Gore-Tex garments cost about twice that of neoprene coated nylon) and, of course, the greatest profit.

As clothing, Gore-Tex does its thing best in hot, dry air—precisely when it would be least desirable because of the enormous heat load it would cause. In cool, wet weather it works best when the user is not exercising vigorously. The ubiquitous tan rain­coat seen on every commuter who ever wore a white collar would seem to be a perfect, huge market. So would the market for golf jackets, car coats and wind breakers when these products are used for casual activities such as walking and spectating.

Mountaineers who must have outerwear that is both windproof and waterproof, and who spend long periods of time (days or weeks) wearing the same garment are prime candidates for Gore-Tex gear. True, they will not stay dry when exercising vigorously. But at least their sweat-soaked cloth­ing may eventually dry out, especially if the climb­er sleeps in his Gore-Tex suit. Body heat will drive the sweat into the sleeping bag where it will con­dense. Then, if the bag gets warm enough during the day, it too can dry out.

Kenneth A. Reinhart of the Natick Army Center who has studied extensively the potential of Gore-Tex-type materials for military clothing says Natick sees these as promising new materials and concepts and currently has such materials under intensive investigation and development for wet weather and cold wet weather clothing. Mr. Reinhart suggests that the moisture vapor permeable, water impermeable materials may work particular­ly well to allow damp clothing and equipment such as sleeping bags to dry while worn or backpacked. He referred to the British experience in the Falk­land Islands war where Gore-Tex-type gaiters pro­vided better service than conventional imperme­able gaiters under very damp conditions. The Army is also interested in Gore-Tex-type materials for use as footwear uppers for waterproofness and in cold weather gloves and balaclava where windproofness and waterproofness are required.

Very strong performance claims have been made over a number of years in millions of dollars worth of advertising for Gore-Tex products. Practically no realistic testing has been published to substan­tiate these claims. Objective testing that has been conducted, primarily by the military, has been equivocal in its outcome.

Yet, not a single article or letter has ever been published by any outdoor or sporting magazines to cast a shadow of a doubt on the workings or effi­cacy of Gore-Tex. Nor has there been any significant comparison of Gore-Tex's performance to competing waterproof/water resistant/breathable systems such as simple impermeably coated fabrics or (silicon) treated materials.

It is hoped this informal report will spur additional debate and research on this subject which is of such strong interest to fellow sportsmen and women.    

[End of Summit article.]

Here is another take on the Gore-Tex myth: http://slate.msn.com/id/2085417/#ContinueArticle

[Ed note: People who still want wind and water resistance for every-day use should investigate the old-fashioned waxed cotton jacket. Here is a material that does breathe when dry.  While not nearly as wind and waterproof as Gore-Tex or simple (inexpensive) urethane-coated nylon, it works just fine for keeping dry in moderate rain for shorter periods of time.  Most importantly, unlike Gore-Tex, it really does breath, so you reduce the sweatiness so prevalent with all Gore-Tex garments.   And it's rugged, durable and looks really cool.]

 Click here for a brief history of waxed cotton.

[Ed note 2:  A second type of breathable outerwear is the tried & true "60-40 cloth" (60% nylon, 40% cotton).  It's drawback is that it, too, is not really waterproof.  But its water resistance can be improved by soaking the entire garment outer with the silicon shoe waterproofing liquid, available at many shoe repair shops. Be sure to soak the entire outer, because otherwise you'll get a stain line where you stopped.  The stuff smells vilely, but that disappears after the solvent evaporates. The silicon coating causes rain to bead up and keep you dry longer. (But, eventually it, too, will soak through.) But it really does pass air.]

[Ed note 3:  The net-net is this: No garment is breathable and waterproof --full stop.  Therefore, you must select outerwear to meet your likely needs.  The best solution in my book is to wear a truly breathable parka for comfort, and carry a cheap, lightweight urethane-coated jacket to don when it really rains.  That will help to keep you dry if you don't exercise . If you do exercise in the rain, nothing will keep you dry, no matter what the million-dollar Gore-Tex disinformation campaigns promise.]