Down feathers
From Wikipedia, the free encyclopedia
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Down is a fine thermal insulator and padding, used in goods such as jackets, bedding, pillows and sleeping bags.
Down offers excellent thermal properties, and has good lofting characteristics. This means that the down traps small pockets of air efficiently. The small pockets of air provide the thermal barrier. Down has the added property that it can be packed into a very small space.
For outdoor equipment, down is considered to be the single best insulating material available due to its light weight, compressibility, and heat retention. Down insulation can be quite expensive, so alternatives, known as synthetic insulation, are available. Synthetic insulation types generally cost less and are usually not as lightweight or as compressible as down. However, synthetic insulations work better when wet and are easier to dry, whereas down insulation does not work well at all when wet and takes a very long time to dry out. Thus people who expect a significant amount of rain when camping will either bring a down sleeping bag with a water-resistant shell, or a bag with synthetic fill.
Down ratings: Down insulation in most outdoor equipment ranges from ~500 to 900, with 900 being the highest quality and most expensive. 500-600 is warm enough and light enough for most conditions; 800-900 fill is used for very lightweight and/or very cold-weather gear. The number refers to cubic inches per ounce of feathers.
When wet or compressed the thermal properties of the down are far diminished. In cold situations sleeping pads are used to provide insulation from the ground for those sleeping in down sleeping bags.
Down can be collected in a variety of ways. Birds which provide the feathers may be used for other purposes, for example to provide meat. Some birds are killed solely for their down, while some birds (particularly some geese) are periodically live-plucked of their breast feathers. Some birds line their nests with down, and such down might be harvested safely after the young leave the nest.
[edit] External links
- Caring for down - Information on maximising the insulating properties of down.
- International Down and Feather Laboratory & Institute - A laboratory specializing in quality control of feathers and down.
- Down with down - Anti-down article from Farm Sanctuary.
- Article about down - Intriguing information about down.da:Dun
