Decoding Down Jackets: From Filling to Loft, Unraveling the Secrets of Warmth

Decoding Down Jackets: From Filling to Loft, Unraveling the Secrets of Warmth

What is filling?

As the name suggests, for down jackets, the filling material inside is down. Down refers to the closest and warmest part of the bird's body, which is the softest keratin fibers.

Down is further divided into: white goose down, gray goose down, white duck down, and gray duck down.


Decoding Down Jackets: From Filling to Loft, Unraveling the Secrets of Warmth

The differences between them are as follows:

1、color: White down is widely used for light-colored fabrics, it is not transparent. However, the color difference has little impact on warmth and comfort.

2、goose down and duck down: In fact, goose down is superior to duck down in terms of warmth and comfort, so goose down-filled jackets are naturally more expensive than those filled with duck down.

Left: Goose Down Right: Duck Down

Left: Goose Down Right: Duck Down

In general, goose down is better than duck down mainly for the following reasons:

Larger clusters: Goose down has longer fibers, larger clusters, and higher loft, and higher loft indicates better quality of down jackets.

Fuller clusters: Geese usually take at least 100 days to mature, while ducks take about 40 days, so goose down clusters are fuller than duck down clusters.

Superior loft: Goose down has smaller filaments evenly distributed on the feather branches, while duck down has larger filaments concentrated at the tips of small feather branches. Therefore, goose down can create a larger loft space, resulting in better loft and stronger warmth.


Better resilience: Goose feathers have better curvature, they are finer and softer than duck feathers, and they have better elasticity and resilience.

Odorless: Geese mainly eat grass, while ducks are omnivorous, so goose down has less odor, and with proper processing, it has little to no smell.

Longer lifespan: Goose down has a longer lifespan than duck down. Goose down can last for more than 15 years, while duck down lasts about 10 years.

In summary, the order of quality and price from high to low is: white goose down > gray goose down > white duck down > gray duck down.

The down jackets we wear are not purely filled with down, but with a certain proportion of down and feathers. This introduces an important concept: "down ratio."

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What is the down ratio?

The down ratio refers to the percentage of down in the total filling of a down jacket. If a down jacket has a down ratio of 90%, it means that down accounts for 90% of the filling, and the remaining 10% is feathers.


Generally, if the down ratio is below 50%, it cannot be called a "down jacket." In the same conditions, a higher down ratio provides better warmth and naturally comes at a higher price.

However, the down ratio is not the only factor determining warmth and price; there is also "fill power."

What is fill power?
Fill power refers to the weight of all the down filling in a down jacket, specifically the weight of the "down" inside the down. It is different from the previously mentioned down ratio, which is a proportion, while fill power is a simple weight value.

Fill power is a key factor in determining the quality and thermal performance of a down jacket under equal conditions (type, loft, fill power, etc.). The higher the fill power, the better the thermal performance of the down jacket.

The fill power largely determines the purpose of a down jacket. Following the principle of choosing according to needs, down jackets are divided into four levels based on their thermal performance, although this is a rough classification.

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Extreme Level (-50°C to -20°C):
Suitable for extreme environments such as the North and South Poles and climbing snow mountains. They are usually one-piece suits with a fill power of 800 or higher and a down ratio of 300g or more.

Severe Cold Level (-30°C to -15°C):
Thick jackets filled with 650-750 fill power goose down, with a fill weight of around 200-300g.

Regular Level (-20°C to -5°C):
The most common level, typically filled with 600-700 fill power goose down, with a fill weight of 180-250g. This is the level of down jackets most commonly worn in daily life.

Light Cold Level (-5°C to 0°C):
Usually filled with 600+ fill power goose down or duck down, but with less fill weight.

What is loft?
Loft, also known as fill power (FP), is generally categorized as 550, 600, 700, 800, or 900 FP. The loft of down plays a role in determining whether a down jacket is warm or not.

Due to its high loft, down fibers have more air trapped in the fiber gaps, and air is a poor conductor of heat. As a result, the warmth emitted by the body is retained, leading to excellent insulation. In terms of warmth, higher loft is better. However, wearing a down jacket with a fill power of 600 or 700 is generally sufficient, while in extremely cold regions, down jackets with a fill power of 800 or 900 can be worn for extra warmth.


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