You want warmth without weight? For 125 million years, the answer has been down. You know, feathers.
It was somewhere in northern China 60 million years before T-Rex walked the earth when a small dinosaur called Dilong paradoxus sprouted feathers – single-filament proto-feathers, to be precise. Scientists say they weren't for flight, but insulation.
Fast forward through a few eons of evolution to 1953, and you'll find the highly complex filament structures of waterfowl down in the sleeping bags of Edmund Hillary and Tenzing Norgay on Everest's South Col. It wasn't long until the miracle fluff found it’s way into cold-weather mountaineering gear of all kinds, unlocking access for climbers and skiers to the harshest places on the planet.
But for all down's powers, it has its kryptonite: water. Just a tiny bit of moisture collapses the structures that loft and trap air, crippling down's ability to insulate. And to make matters worse, it takes a very long time to dry.
So how do birds keep from freezing to death? For one, they've evolved contour feathers that layer like shingles, which they cover with a waxy oil excreted from their preen glands to create a waterproof shell. And birds have no sweat glands, so their down won't wet out with exertion.
It's a little trickier for humans. A GORE-TEX® membrane can waterproof the outside of your down jacket from rain and snow, and that will breathe well enough to handle the output of your many, many sweat glands. But if it’s cold and you slip on a creek crossing, or your packed-up jacket gets hit with a water bladder leak, you could be in serious trouble.
The U.S. Army saw the threat, and in 1983 commissioned the company that would become PrimaLoft® to create a waterproof alternative to down. What they invented was a patented synthetic microfiber comparable to down in warmth and durability that retains its insulating ability even when drenched. But it fell short of down's characteristics in terms of loft, compressibility, and lightness. Each new generation of PrimaLoft has closed that gap, but down still edges synthetics in those comparisons, and that left room for innovation.
That's why scientists and outdoor gear makers spent the last two decades trying to develop hydrophobic treatments that could coat down's filament structures and help them stand up to the surface tension of water. In the last two years, a couple of these products have made it to market, but we tested them in Gore's state-of-the-art laboratory facilities and found unsettling problems with durability, especially after washing.
We couldn't in good conscience send you into extreme conditions with a promise to keep you warm when wet, if we couldn't deliver on that promise 100%. So we poured our efforts into lab- and field-testing every water-resistant down product and prototype available, but there was nothing we could really stand behind.
Then PrimaLoft sent us prototypes of their Down Blends.
The first time you see PrimaLoft Down Blend, it just looks like a pile of little white tufts. You grab a handful and a bunch of them escape, spinning out and floating on the drafts your hand just made, and there in your palm is maybe the softest, coziest thing you've ever felt. Which makes it easy to forget how advanced and effective this material really is.
To understand what you're actually holding, it helps to think of each little cluster as the Terminator – in Arnold's words, "a cybernetic organism, living tissue over a metal endoskeleton." The little cluster's "endoskeleton," though, is the elegant filament structures of waterproof-treated down. The "living tissue" is hundreds of ultrafine synthetic fibers that intertwine with the down’s microscopic structures to form an intimate bond. This is more than just down on steroids.
In fact, the bond between down and synthetic fibers is so strong that when it was tested by international lab that verifies whether insulations meet industry standards, they found hardly any synthetic material. The initial report put the mix at 95 percent down. But that wouldn’t explain its unique ability to insulate when saturated. So they tried another test, this time using a chemical compound that dissolves feathers, but not synthetic fibers. What was left was pretty astonishing: a pile of synthetic insulation equal to 40 percent of the clusters that had been dissolved.
It’s this 60/40 bonded mix that allows PrimaLoft® Down Blends to give you insulation, even when soaked, while performing nearly identically to down in terms of compressibility, loft, and warmth-to-weight ratio. And if you drench it, relax. It dries four times faster than untreated down.
So after 125 million years, we finally have down without the letdown. Last year, Sitka became the exclusive hunting launch partner for PrimaLoft® Down Blend. The pieces for brutal cold that will keep you warm when wet – no matter what – are: