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<\/p>\nDown jacket fabric splits into two very different jobs: the shell that has to do the windproof and water-resistant work, and the lining that has to feel light against the body. Both have to be tight enough to stop the down from migrating out, which makes them some of the most technically specific fabrics a mill weaves.<\/p>\n
A down jacket works because a sealed shell traps the down inside. The outer shell is a high-density woven with a tight construction that blocks wind and, usually with a finish, resists water. The lining is a lighter, softer weave that does not need to be waterproof but has to be dense enough to keep the down tufts from working through the threads. The density of the weave, measured in thread count or denier, is what keeps the down in place.<\/p>\n
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The key spec is not how heavy the fabric is, but how tightly it is woven. A down fabric uses a fine denier yarn in a very tight weave, so the gaps between threads are smaller than a down tuft. If the weave is too loose, the down feathers push through over time, which is the familiar “leaking feathers” problem. A 20-denier to 40-denier nylon or polyester with a high thread count is the common profile for a lightweight down shell.<\/p>\n
Most down shells get a DWR, or durable water-repellent, finish that makes water bead and run off. A lighter-weight fabric may also take a slight coating to close the weave further, though coatings reduce breathability. The trade is between water resistance and how the fabric breathes out the body’s moisture, which is why a down jacket for a wet climate is finished differently from one for dry, cold weather.<\/p>\n
Give the mill the denier, the thread count, the weave finish and the DWR treatment, and state whether the cloth is the shell or the lining. On a custom down-jacket fabric, the same technical points that hold a jacket structure<\/a> also decide whether the down stays put. Confirm the zero-feather-migration point on a physical sample, because that is the one failure a buyer cannot see until the jacket is worn.<\/p>\n<\/div>\n