Down is a type of feather that is found on most waterfowl. It is the layer between the outside feathers and the bird’s body. Down has the important function of keeping the bird’s body warm. It does this by insulating the bird’s body from the outside temperature. The light fluffy feathers create many tiny air pockets. The outside temperature is prevented from reaching the water fowl because it cannot move easily through the many air pockets.
There are a number of characteristics that make down very useful to humans. The first is its insulating properties. Down, when placed in a coat or a comforter, has the same insulating capabilities that it does on a goose. It keeps warm air trapped near the body and cold air out. Down is also very soft. It is a simple feather that looks like a puffy cluster. These feathers are without barbs and have only a very small rachis or shaft. Because all of the air pockets found in the feathers, down is light and compressible which is ideal for camping gear, such as sleeping bags and jackets. One drawback of down is that it loses its insulating capabilities when soaking wet. Wool is much better at insulating when soggy than down.
Fill power and fill volume
Two ways of measuring the amount and quality of down in products are the fill power and the fill volume. Fill power is measured by a weight pressing compacting the down in a very climate controlled cylinder. It is measured in cubic inches per once. Medium quality down is around 400 and anything over 750 is very high quality. In these high fill power products the clusters of down are larger, giving them the ability to insulate to lower temperatures while remaining lighter and fluffier. This number is especially important for camping products, where weight is a significant advantage. For items such as comforters, fill power is not as significant. Fill volume is how much volume is used by one once of down. This number is rarely used to advertise down products, but it is important not to confuse it for fill power.
One disadvantage of down is that it may cause problems for those that suffer with allergies. Very few people are allergic to the goose down itself. However, the structure of down naturally gathers dust mites and other allergens. Fortunately, there are alternatives. There are many synthetic fibers that closely imitate down and are just as fluffy and warm. There are also hypoallergenic down products in which the down is cleaned and and the product constructed in a way that can prevent allergens from collecting in the fine feathers.
If you are searching for light, fluffy and warm, whether it is a coat, comforter or sleeping bag, down is an excellent choice.