Testing Down
When delivered to the manufacturer after cleaning and sorting, down bears little resemblance to the mucky substance that was gathered after plucking. Testing of this finished product takes place either by the suppliers or by the manufacturer or both. Suppliers carry out several tests, two of which are of interest to users in the outdoor trade. The better manufacturers will then check what they are getting by repeating the first test (fillpower) for themselves.
Fillpower
This is the test one hears quoted the most and by far the most useful of the laboratory figures. There is no single 'World Standard Fillpower Test'. Each country uses its own system: UK, USA, Japan, Sweden, Germany, etc. The basic elements of the tests are however common to them all.
The down is fluffed up by an air blower, then kept at a controlled temperature and relative humidity for a minimum of 3 - 5 days. Then a sample of the down is taken (20gm, 30gm or 1oz depending on the test) and fluffed up again in the test cylinder. Then a disk of a set weight is lowered down the cylinder to level off the top of the down and the depth of the down is measured.
This establishes the volume which a measured weight of down will fill - the fillpower - whether stated in cubic inches per ounce or cubic centimetres per gram. Cubic inches per ounce is the scale most often quoted the American influence dominating even in metric countries. So when people talk about 550, 600, 700 fill they mean 550 cu in. per oz, etc.
PHD uses a Lorch machine for fillpower testing. This is as near to being an accepted 'world standard test' as there is at present and is approved by the International Down and Feather Bureau. The standard Lorch test uses 30 gm of down, so when quoting cu. in. per oz (one ounce is 28.34 gm) there is an apparent overstatement of fillpower by nearly 6%. However the Federal (FCT) test in USA uses a narrower cylinder and a much lighter top disk, with the result of the same down, one ounce (28.34 gm) tested by the US Federal method, is likely to be given about a 4% higher fillpower figure than 30 gms on the Lorch. So we don’t adjust the figures from the Lorch test, up or down, and we are still about 4% more conservative than US Federal tests.
As a guide to the meaning of fillpower figures:
- 400 Is a normal grade down for bedding or the bottom end of the sleeping bag market, often with more than 15% feather.
- 500 Is already quite a reasonable down, mid to top range for suppliers of cheaper bags.
- 600 A very good down; any supplier is having to work at it to find and maintain this level.
- 700 This is a rare and expensive product. Very few goose downs achieve a higher fillpower than this and for duck down it is the very top limit.
- 800 Achieved by very few downs in the whole world.
Down/Feather Content
Measured by hand picking. Every single piece in a very small sample of down is separated into categories such as down, down fibre, downy feathers, feathers etc etc. Each category is then accurately weighed. (I work with scales accurate to one thousandth of a gram) and the down content then stated as percentages 90/10, 80/20, etc. As a higher first figure means a higher down content, this test is often quoted as another promotional statement about down quality (even 100% has been claimed). Unfortunately that is often the main value of the test - a promotional statement - because there is no single international standard by which these figures are produced and the degree of possible variation makes them virtually meaningless.
As an example, you would be wrong in assuming that a '90/10' down always contains 90% down. In the first place what classification of the word down is being used - how much does it include of the middle categories between pure down and pure feather? There are guidelines, but no accepted worldwide standard and differences in classification exist. Second and even more confusing, by the US Federal Standard the actual down content only needs to be 72% to get the 90/10 classification. It is not that the US standard is lower or less precise: it is just the use of words which catches you out. Some other national standards (German, British, etc) are more in line with what you would expect, but US figures are often used by Far East producers, whose goods go all over the world. And third, measuring down content is a long tiresome business, only applied to the tiniest fraction of the down being processed: it gives a rough guide only and the figures are unlikely to be checked.
In the end the only way for a manufacturer to be sure of what he is saying is to do picking tests himself: and even then he is likely to be spending a lot of time in testing .001% (one part per 100 thousand) of what he uses.
Overall it is better to treat down/feather figures as comparatively unimportant. An experienced manufacturer can tell immediately if there is any increase in the feather content of a down and it will also show up adversely in fillpower testing. After all if extra feathers improved the fillpower, who would care about the classification of the material?
