Talk:Fill power

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This article is a mess. It contains three different units for measuring fill power haphazardly without comparing them, or even acknowledging each other. I am unfortunately not qualified to correct it--Mongreilf (talk) 09:44, 25 October 2008 (UTC)

12 years later, Mongreilf, and still no closer to a reliable explanation. :-(

I suggest replacing the first section with the following paragraphs. Jim010203 (talk) 06:07, 30 November 2013 (UTC) jim010203

"Fill" is the light-weight, goose down or synthetic material that fills the inside of sleeping bags, pillows, quilts and cold-weather jackets. Fill power is a measure of the loft or "fluffiness" of the goose down or synthetic fibers. It is related to the thermal insulating ability of the product. Its usefulness is in making rough, relative comparisons between similar products. A jacket made with insulation of a higher fill power will keep the wearer warmer than the same jacket made with insulation of lower fill power.

The fill power number (or rating) represents the reciprocal of the mass density of the fibers making up the insulation. Mass density is mass per unit volume. In the international system of units, mass density can be given in grams per cubic centimeter. So the reciprocal mass density is cubic centimeters per gram. In the U.S. customary system of units, fill power ratings are given in cubic inches per ounce. Regardless of the units, the rating is determined by placing a known mass of the fibers in a cylinder and measuring the volume the fibers occupy under their own weight and the weight of a standardized lid (or piston) that fits inside the cylinder. The piston provides a level surface from which an accurate volume can be measured. To a good approximation, one cubic centimeter per gram equals 1.723 cubic inches per ounce. Coarse feathers have a low amount of loft. If their fill power is rated at 300 cubic inches per ounce, this converts to about 175 cubic centimeters per gram. Currently, the highest fill power rating is 900 cubic inches per ounce for very fine-grade goose down.

Higher fill power makes the product better insulating by creating many more small "dead-air" spaces (or cells) in the volume of space between the fabric next to the skin and the outer fabric layer. Heat transfers (or more traditionally "flows") from a warmer object to a colder object through four mechanisms: vaporization, conduction, convection and radiation. Radiation refers to infrared, electromagnetic radiation which is continuously produced by the molecular vibration of all objects with a temperature above absolute zero. The best way to reflect infrared radiation is to use a shiny, aluminized fabric or material. Over the years, garment and sleeping bag makers have tried to use reflective fabric for an inner lining with decidedly mixed results.

By contrast, dead-air cells in a fiber-filled sleeping bag reduce the convection currents that develop when (less dense) warm air rises vertically and displaces colder air. The displaced cold air then circulates to the side wall of the cell. The colder side walls cool the displaced air (through conduction). The now cooler air sinks back to the bottom of the cell creating a closed circuit (a convection current). The smaller the cell size, the smaller the convection currents and less heat flows. In the 1990's, manufacturers began to add synthetic fiber fill to the inflatable air mattress to create a sleeping pad for campers and backpackers that is much warmer than a large slab of air prone to convection currents. Most recently companies are working to give goose down water repellency to overcome its main weakness: losing its loft when wet from rain or evaporated sweat.

Jim010203 (talk) 05:53, 30 November 2013 (UTC)jim010203

"harvested"
Would anyone object to changing "'harvested' for food'" to "slaughtered for food." Slaughter is well understood and requires no quotes. Thanks, all. james

Still a inaccurate mess after all those years
Apologies, as much as I would like to attempt a rewrite with sources, no time for that atm. So I'll just (helpfully or not, not trying to be condescending here) point out a few things that could be improved, sorry for that.


 * 1) EN 13537 is no longer used, it's been long superseded by ISO EN 23537:2022 (latest revision, first revision probably 2016)
 * 2) Sleeping bags FP section here? Might be better just in sleeping bags article, not in fill power? But OK.
 * 3) ISO EN 23537 (and neither the older norm) doesn't rate "the lowest comfortable temperature". That's never been true. The norm explicitly rates a range of temperatures, where Tcomfort denotes the range where the average sleeper would be comfortable on their back, Tlimit the range where the average sleeper would still be able to sleep in a curled up position and Textreme the range where the average sleeper will survive the night without hypothermia, though perhaps not asleep (roughly paraphrased). That's an important distinction, since "the lowest comfortable temperature" doesn't take sleeper differences into account, while a range inherently does. That's why the norm mandates not just a single number, but a graphical representation of the ranges.
 * 4) Washing and restoring – Wiki is not a recipe book, is that needed? Anyway, "The idea is to open up the matted down clusters with warm air and moisture." is not correct either, as it's the mechanical agitation after washing (or compression) that restores loft. Feather barbs and barbules tend to entangle together and a lot of mechanical energy is needed to free them, not just warm air or moisture.
 * 5) More importantly, the FP measurement section is outdated and even back then, missed out quite a few things. The US 2013 method of steam conditioning often resulted in different FP measurements than the than EN method of dry conditioning, making them directly incomparable (e.g. a 850 FP result by the US method equivalent to 800 FP by the European method, quite an important difference). IIRC there are newer methods being adopted by now, but not sure if and how their ratings are comparable anyway and which are used where.
 * 6) Just a suggestion for citations – please use industry journals, scientific papers and similar higher quality sources, as retailer articles like REI (even if that one ain't bad) are often inaccurate, outdated or can perpetuate myths or marketing.

Technicality nitpicker (talk) 20:15, 15 February 2024 (UTC)