It takes more than a set of tweezers to separate down from feathers. It also takes an eagle eye.

The plucky staffers at the International Down and Feather Laboratory & Institute have those. Training can last three to six months before they're certified as down and feather analysts — experts who spend their time gandering at samples and separating the delicate little puffballs from down fiber, feather fiber, residue, feathers, quills and anything else.

"There's no way to automate it," IDFL's president, Wilford Lieber Jr., said of the separation process, which can take two to five hours.

The second part of the separation process involves scanning the down clusters with a microfiche to see if they're just ducky or if the samples came from another bird. Tiny strands in the clusters sport nodes whose shapes indicate if the down came from a goose, duck or landfowl.

IDFL can do other testing, too. Fill power tests check the insulation ability of down products. Those require samples sitting in boxes for 72 hours at a specified temperature and humidity.

Using a cylindrical device, IDFL staffers determine loft, or insulation ability. A certain fill power number, usually on the product packaging, gives the buyer an idea of whether they'll shiver inside a sleeping bag.

"The trick in insulation is air spaces," Lieber said. "Air traps the heat. The best insulation is trapped air."

Downproofness also can be checked to ensure the down won't slip through the containing material. Downproof fabric keeps out dust mites, which feed on human scales left on the surface of pillowcases and sheets. Loose fabric allows the mites to live inside.

Lots of other tests can be done. Oxygen levels indicate cleanliness. A test for turbidity examines how much dirt or dust is in the sample. Fat and oil levels also can be figured — certain levels can lead to odors in humid conditions, but too little can leave the product flat.

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