Down Basics
Down is easy to sell with adjectives and hard to compare without numbers. This page explains the four numbers we publish on every product, what each one means, and how to read them together — on our jackets or anyone else's.
Goose down, and how it is processed
Most down jackets on the market are filled with duck down, and good duck down makes a good jacket. At least three quarters of the world's down supply is duck. Goose down has properties of its own: larger clusters that reach higher fill power, more warmth for the weight, and very little natural odor.
Our down comes from northern white geese, raised in cold climates. Their large clusters have dense, finely branched filaments that trap more air and keep their loft.
How down is handled decides how much loft it keeps. Sounor down suppliers work in six stages.
Color sorting
Off-color feathers removed.
Dust removal
Before and after washing.
Multi-stage washing
Hot water, mild detergent.
Drying and sterilization
High heat, controlled moisture.
Single-batch finishing
Never re-blended. Nothing added for weight.
Third-party testing
Independent lab: fill power, down content, odor, cleanliness.
Species is only part of the picture. Compare it together with fill power, down content and fill weight.
Our jackets are filled with goose down.
How down keeps you warm
Down is not warm by itself. What keeps you warm is air: still air, held close to your body, where your own heat can warm it and keep it warmed.
A down cluster is a three-dimensional tangle of fine filaments that traps a great deal of air for its weight. The more air it holds, and the better it holds that air in place, the warmer the jacket. Everything below is a way of measuring that.
Fill power
Fill power measures how much space a given amount of down occupies — how fluffy it is.
It is a laboratory measurement. One ounce of down is placed in a cylinder under a lightly weighted disk, and after one minute the volume it fills is recorded in cubic inches. 700 fill power means one ounce of that down lofts to 700 cubic inches.
Most down apparel falls between 550 and 800. Around 900 is the practical ceiling of commercially available down, and it is usually reserved for expedition and ultralight equipment where every gram is accounted for.
Higher fill power is more efficient, not automatically warmer. It gives you more loft per gram, which means a lighter and more compressible jacket at the same warmth. It tells you nothing about how much down is actually in the garment.
Down content
Down and feathers come from the same bird and do different jobs.
Down is the soft cluster — three-dimensional, with no quill. It traps air. A feather has a stiff central shaft, adds weight, holds very little air, and can work its way out through the shell fabric.
Down content is the ratio between the two, usually written as a pair. 90/10 means 90% down cluster and 10% feather. Most down apparel falls between 75/25 and 90/10. The split is determined by accredited laboratories such as IDFL rather than estimated by the maker.
A higher down content means more of the jacket's weight is doing insulating work. On its own it does not tell you how warm the jacket is — that still depends on how much is inside.
Fill weight
Fill weight is the mass of down inside the garment, in grams.
Fill power describes the quality of the down; fill weight describes the quantity. Warmth comes from both.
As a rough map: light packable jackets carry 60 to 120 g, everyday winter jackets sit around 150 to 250 g, and expedition parkas go past 300 g.
Fill weight changes with size, since a larger garment holds more down. A published figure only means something if the reference size is stated with it.
Temperature
A temperature rating tells you the range a jacket is built for. Comfort is where most people stay warm standing still, with a normal layer underneath. Limit is where you begin to feel cold but remain protected while you keep moving.
Down apparel has no certified temperature standard. Sleeping bags are tested to a published method; jackets have no equivalent, so every jacket rating on the market — ours included — is the maker's own figure rather than a laboratory result.
We publish ours and say plainly what it is. Wind, how hard you are working, and what you wear underneath will move the range in either direction.
Reading the numbers together
Two jackets:
A uses better down. B is warmer. A is lighter and packs smaller; B holds more insulation. Neither number on its own would have told you that.
Fill power alone cannot answer how warm a jacket is. Ask for both numbers.
What the numbers do not cover
Construction. Down has to be held in place. In sewn-through construction the outer and inner fabrics are stitched directly together, forming quilted channels — light, packable, and slightly cooler along each seam where the insulation is compressed. In box-wall construction a strip of fabric separates the two layers, letting every chamber loft fully with no compressed seams — warmer, heavier, more expensive to make. Neither is better in the abstract; they are built for different temperatures.
Shell fabric. A shell that blocks wind and sheds light rain keeps the down dry and the warm air in. Wet down does not loft, and down that does not loft does not insulate.
Fit. A jacket too tight compresses the down against you. A jacket too loose gives your body more air than it can warm. Neither shows up in any specification.
Before you buy any down jacket
Five questions. They work on any brand, ours included.
What is the fill power?
What is the down content?
What is the fill weight, and at which size?
What temperature range is it built for, and who determined it?
What is the construction, and what is the shell?
Caring for it
Down lasts a long time when you mostly leave it alone. Washing, drying and storage are covered in full on the Care page.