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Breathing Underwater

Mike Clifford

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Reading Scott's post regarding waders that leak, and not currently owning a set of breathables myself- it was time to turn to the almighty internet to seek out that which I should be throwing my hard earned money at.


Which brought me to the following page:

Breathing Underwater


Most definitely worthy of your time, even if you already think you know everything there is to know about waders.


The road to creating the high-tech fabrics that keep you dry in the water has been long and winding ... and there's still a ways to go.


The cutting edge of fly-fishing product design—the main battlefield, if you will—is in breathable waterproof fabrics. Ever since anglers flopped out of the primordial muck of cotton and rubber and began evolving towards the sleek, modern creatures we are today, breathable products have differentiated the fly fisher in the know from his Neolithic brethren. The cotton clothing our granddaddies used was great at breathability but pretty darn poor at keeping out water, even if you waxed it. Plain old rubber, and then neoprene, offered flyfishers the ability to remain dry underwater, but at the cost of a complete lack of breathability, which led to wet, cold bodies and the potential for surprise hypothermia. The body’s own sweating and cooling mechanism worked against it, creating discomfort and danger. The invention of breathable waterproof fabric offered a way to keep liquid water on the outside while allowing water vapor (sweat) created by the body to make its way outside, as well. This remarkable technology is found in most products on the market today. Breathability keeps the fisherman dry—as well as warm or cool, as the case requires. Scientifically, most products achieve this magical feat by sandwiching a microporous membrane between an exterior and an interior fabric. (The interior fabric provides comfort, while the exterior fabric provides durability.) Some microporous membranes are created in sheets, like cloth, and glued between the covering layers. Others are applied in a “knife over” technique, which basically means they’re squeegeed directly onto one layer of fabric, smoothed out, and then covered with the other layer. As the name suggests, microporous membranes have many tiny holes in them. On a molecular level, these holes are big enough for water vapor to pass through, but small enough that liquid water molecules can’t fit through the same holes. Thus, water vapor can go out, but liquid water can’t come back in. (Kind of like how your cat door won’t admit your muddy Labrador.)


That’s what any breathable fabric does: it acts as a one-way door for water vapor......

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