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

Keeping yourself dry when the air around you isn't is an old problem, but the last few decades have seen significant improvements in waterproof outerwear.


| March/April 1990



Mark Twain Crossing the Ohashi Bridge

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


ILLUSTRATION: JAN ADKINS

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 Andō 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.





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