Rain Gear to Keep You Dry: How it Works and What to Look For

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Mark Twain, ever an Innocent Abroad, crosses the Ohashi Bridge in a Moonstone Jacket.

When the elements question our right to prowl outside our caves, when even the leopard is crouched in a burrow to keep dry, then our outer skins must become more than finery. Clothes must work, and the quest for the perfect rain gear–lightweight, comfortable, waterproof outerwear that keeps us warm but doesn’t trap body heat–is still ongoing.

I am looking at a color print by the 18th-century Japanese master And? Hiroshige, The Great Ohashi Bridge Under the Pouring Rain. In a driving, cold rain a half dozen citizens hurry across the exposed arch of the bridge. Two women ward off the rain with broad traveling hats, though I can see that their bright silk kimonos will be soaked, and they may be furious enough to beat their servants when they get home. One man stumps along under an old tatami mat, a good idea, but he will have to be fairly athletic if the wind (which is calm) picks up. A trio of workmen have taken off their trousers and are walking in bare feet under a large ribbed umbrella; they will have a chilly but convivial walk and nothing will be ruined. One barelegged man seems to be struggling with the thick cotton of his smock, wet beyond the brim of his conical straw hat. Coming downstream and soon to pass under the bridge is a waterman poling a narrow lumber raft. He is also wearing a conical straw hat and a woven-grass rain stole that makes him look like a long-legged hedgehog.

These men and women from feudal Japan illustrate several of the difficulties of keeping dry when the air around you isn’t.

The Challenges to Effective Rain Gear

The highborn ladies are discovering that the fabrics that drape well and comfortably in a garment are, by their nature, absorbent. As the moisture wets them to their highborn skin, they will also find that water efficiently conducts heat away from the body and chills them. There were only a few materials available in 18th-century Japan or Europe that were waterproof and flexible enough to wear. Linen was sometimes impregnated with beeswax to make a waterproof cloak, and coats like these are made today by Barbour in the United Kingdom. They have the expensive appeal and clunky lines of a Range Rover, but they are not terribly durable or versatile, and I wouldn’t hang one next to your white silk kimono in the closet.

The chap under the tatami mat has a thick shield between him and the downpour. It should work, for a while, and he has his own little tent under it. One of the most effective pieces of rain gear is the poncho, a flat sheet of coated fabric that folds over the shoulders, has a pop-up hood in the middle, and lots of room inside. Because the tatami and the poncho are impromptu kites when the wind blows, practical hands slimmed the poncho profile and made a cagoule, a large hooded bag with sleeves that slips over the head and comes down below the knees. The poncho and this walking tent have advantages. There is enough room inside them to promote circulation.

The three mates under the umbrella are moving right along, trying to get under cover. They are discovering the hardest thing about staying dry while making any effort in the rain: Even in this chilly scene they will begin to sweat. When rubber found its way from the jungles, we had a perfectly waterproof covering. The rain gear that professional fishermen use today is often the stiff, almost bulletproof Black Diamond gear or Helly J. Hansen’s robust rubber-and-polyurethane bib sets. Unfortunately, shutting out the elements doesn’t keep anyone dry. A human body performing light to strenuous exercise regulates the critical temperature of its cells by throwing off one to two pounds of water vapor each hour sweating. The vapor passes from the skin and through porous, absorbent clothing. As it moves away from the body it loses heat (which is what it’s supposed to be doing). At some point it will reach its dew point and condense, either on the inside surface of the cooled rubber or somewhere in the clothing. The inhabitant of this two-way water barrier will be soaked in a short time. Then the water will carry heat away from the body even more efficiently through the damp clothing, and chill will set in.

I wish there were someone who looked comfortable on the bridge, because staying dry begins to look hopeless. The fact is, keeping dry was not asked of clothing until the last few decades. We have an exaggerated expectation of comfort. As an example, oilskins (canvas soaked in a polymerizing oil) worked as well as any sailor expected them to work. He knew that they leaked at the seams, soaked him with his own sweat inside, and made him smell like the back room of a taxidermy shop, but he was only concerned with staying warm. He trusted wool serge pants and wool sweaters to insulate him even when they were damp. And, come to that, he didn’t mind the cold as much as you do.

Waterproof Clothing Basics

The best example of weatherproofing by weight is the trench coat. What a piece of work the real article is! Six hundred buttons, a foundry output of metal rings and buckles, epaulets, room enough to rent space. The collar buttons up to the nose, the wrists adjust, the pockets are deep, the waist cinches flatteringly, and there’s a shoulder patch for your Enfield rifle. Trench coats are built in a tightly woven wool twill that sheds water for hours. Designed to keep men in some kind of comfort while they marched or stood in trenches, the coat is heavy and cumbersome–and once the shedding hours are up, it lets you know.

Technology began to tinker with the possibilities of a “breathing” coat in the early ’60s. The familiar sierra coat was made of a fabric blend of 60% cotton for breathability and canvaslike repellency and 40% nylon for strength. The theory sounded good: The coat would breathe while water beaded on the surface until the outer fibers absorbed moisture and swelled, held in place by the stronger, less permeable nylon. Water would be excluded, but water vapor would pass through. In reality this coat kept its inmate dry for about five minutes in a light mist, but it was so damned useful and handsome that it’s become a classic light coat for cool, sunny days.

The W. L. Gore company does not manufacture rain gear, shoes, or gloves. They have perfected a film, thinner than a communion wafer, that has interesting properties. It is made of a synthetic polymer that is hydrophobic (it will not hold water, or “hates” it) and has a controlled porosity. In every square inch of the film there are 9 billion open pores of fairly consistent size. As a gas, water’s molecular structure is small and passes through the pores. In liquid form, water’s matrix is too large to pass through and is kept on the outside. Another oleophobic layer is added that will not allow body oils to compromise the film’s mechanism. The film is too delicate for use on its own and so borrows strength from the hard-wear textiles to which it is bonded. Bonded, seams taped, tested and approved for water repellency by the W. L. Gore labs, it becomes Gore-Tex for a limited number of licensed manufacturers.

Gore-Tex works, but it is not the end of woe. The film simply can’t deal with all of the body’s output during exercise; some water vapor will condense if it isn’t allowed to escape. In extreme situations the outer fabric’s water-beading repellency breaks down and (sometimes abruptly) conducts heat away from the inner environment more efficiently; the temperature gradient below the Gore-Tex film changes and the dew point location moves deeper into the absorbent layers of clothing. Clothing is soaked with moisture. A clammy cold invades, which may be an occasion for some muttered Anglo-Saxon words in fortunate circumstances, and for genuine danger in critical times.

Choosing the Right Rain Gear

Staying optimistic in the rain is an old problem, older than the bridge at Ohashi, but some extraordinary companies are working on it for you. One of the best is Moonstone Mountaineering. Their Advantage Jacket has a durable outer fabric bonded to a Gore-Tex film. Beneath that laminate it is fully lined to “breathe” better. It has a detachable hood, a drawstring waist, and “pit zips” with double flaps that mechanically vent the hot spot under the arms.

The North Face’s Triplex Jacket protects the high-abrasion, high-rain-strike areas with layers of fabric backed by Gore-Tex and a lining. Its cuffs are adjustable, and its zipper has a snap flap. It is only one of the products that have come out of their ambitious research and testing. The Triplex demonstrates one of the basic wet survival techniques: color. Buy rain gear bright enough to embarrass you just a little in the showroom. In the gray light of a cloudy day, bright colors glow like a uranium stockpile.

Patagonia is also one of the largest and most thorough explorers of outdoor clothing. The Storm Jacket and Storm Anorak are beautifully made and constructed with Patagonia’s proprietary vapor-permeable treatment, H2No. They are lined with nylon mesh and nylon ripstop, and have adjustable cuffs and a drawstring waist. Patagonia works in three repellent grades: H2No Light, very breathable, suitable for heavy activity in light mist or drizzle; H2No Plus, a middle range for wet snow or rain; H2No Storm for cataclysmic downpours and Seattle.

Marmot Mountain International’s Monsoon is a reinforced rain jacket with a Gore-Tex laminate and ripstop/mesh nylon lining. It has a strength of detail and durability gained from Marmot’s background in making mountain equipment.

REI, Recreational Equipment, Incorporated, is one of the largest manufacturers of outdoor clothing. Their Switchback Parka has a Gore-Tex laminate and is half-lined with mesh. It is a sturdy piece of equipment and, as the least expensive rain jacket here, points out that comfort doesn’t come cheaply.

Because a good raincoat is a serious investment, you should be serious about choosing it. Be certain that it is crossover gear–that it is useful in several ways, for several sports or times. It is not too much to ask of these jackets that they keep you well while you are sailing, hiking, skiing, or going to the corner for some oat bran. But also be certain that you do not expect magic. No foul-weather gear without a power supply (NASA is good at these) can keep you dry by itself; you must help. For the best vapor dumping in a cold rain, you should have a hydrophobic layer (like capilene underwear) next to the skin, an absorbent layer beyond (a cotton flannel shirt would do), and an insulating layer between you and the outer skin (wool or synthetic pile). Keep your rain gear clean and oil-free; pay attention to the garment care tags the manufacturer takes the trouble to put on them. Also, zipper failure is all too common, usually the result of grit in the teeth. So blow the zipper slider clean once in a while.

It is still raining on the bridge in Ohashi. The most serene member of the scene seems to be the waterman, poling his raft. He may be humming under his hat. Water vapor goes through his cotton smock and into the grass rain stole easily. His legs are bare. The bridge pilings, still a gray pattern to him, are not a difficult passage. I believe I would like to put on my Moonstone jacket and my Black Diamond pants and join him.