How is fill power measured?
The standard method for testing fill is to put one ounce of down in a standardized testing cylinder and compress it with a standardized piston that fits loosely inside the cylinder. The volume occupied by this partially compressed down is the fill power measurement. To be tested properly the down must be prepared according to a set procedure, and at a defined range of temperature and humidity. A number of tests must be made with down collected from several places in each batch, and the measurements averaged. The most reliable tests are done by certified testing labs. A processor or manufacturer’s test cannot be considered accurate without lab confirmation.
