Fill power

Fill power is a measure of the loft or "fluffiness" of a down product that is loosely related to the insulating value of the down. The higher the fill power the more insulating air pockets the down has and the better insulating ability. Fill power ranges from about 175 cm³/g (300 in³/ounce) for feathers to upwards of 500 to even 580 cm³/g for high quality down. Higher fill powers are associated with a larger percentage of down clusters and a larger average down cluster size.

Measurement

Fill power is the most frequently used measure of down quality. It involves measurements taken of a one ounce sample of down in a plexiglas cylinder with a weighted piston compressing the down. The test requires controlled temperature, humidity, and preparation of the sample. All other things being equal a parka (duvet or sleeping bag) made with high fill power is lighter and more compressible than an equally warm one made with lower quality down. Fill power is expressed as cubic inches per ounce (c.i/oz) -- a lofting power of 400-450 is considered medium quality, 500-550 is considered good, and 600-700 is considered excellent.

700+ fill is quite different from 400 fills. Almost all down commercially available is a secondary product of geese raised for consumption. It would be prohibitively expensive to raise geese for down alone. The geese that are the source for lower fill down are about four months old when they are "harvested" for food. Down from these geese can be carefully sorted, washed, and blended, but it will never loft like really mature down. The 700+ down fill comes from a small number of birds kept for breeding purposes throughout the year. These geese molt naturally in the spring. While their down is loose it is collected by hand. It is very rare and, of course, expensive. The larger individual plumules are what gives the greater loft. The only way to get down of this quality is by careful hand selection which is the major factor in its scarcity.

Insulation and weight

Depending on the intended application, the highest available fill power may not be necessary. A high fill power will provide more insulating ability for a given weight of down. The warmth of a down comforter depends not only on the fill power, but also on the quantity of fill. So the difference between a comforter with 550 fill power down and a comforter with 700 fill power down is that the 700 fill power down comforter will be lighter for the same warmth rating. High fill powers are most important for weight sensitive applications such as backpacking.

European sleeping bags

In Europe, sleeping bags are sold with temperature ratings (in degrees Celcius). The rated temperature is the lowest comfortable temperature. Often a table with tables will be associated indicating safe but potentially not comfortable temperatures. Here are some examples for L size bags:

US sleeping bags

In the USA, sleeping bags are sold by temperature rating (in degrees Farenheiht). For backpacking, temperatures are often 32, 20, 15 and 0 °F.

Washing and restoring

Fill power of down tends to diminish as the down gets dirty and matts. The fill power of a down article can be restored by washing the article in a washing machine with or without detergent (mild) and dried in a home dryer. Tennis balls can be added to help fluff the down. Alternatively, the washing can be skipped and the down article can be placed in the dryer with a damp rag for 10-20 minutes. The idea is to open up the matted down clusters with warm air and moisture.

ee also

* Duvet

External links

* [http://www.idfl.com The International Down and Feather Testing Laboratory]
* [http://www.idfl.com/articles/fillpower.asp IDFL Fill Power Articles] Tons of articles about fill power
* [http://www0.epinions.com/otdr-review-1DB7-2C0C358-384F4182-bd1 Get Your Fill] by Rick_Bin on ePinions.com
*http://www.foundmark.com/pers/gallery/parkas/designer/insulation.html#3