Overview

The most important aspect of quality in a duvet or pillow is the down filling. However, there is a lot of confusion about what down actually is. A water bird grows several distinct types of feathers:

Large Flight feathers are large straight flat feathers for flying. They can be quite long (6", 8", 12" and more) and have a heavy quill, or centre shaft. They are found on the wing and tail.

Small Flight feathers are straight flat feathers also used for flying. They are found interlocked with the large flight feathers to form the flying surface of the wing. They can be quite small, and are also found on the wing and tail.

Body feathers are about 1" to 2" long, and are grown by the bird to protect the body and the underlying down. These feathers form an even layer over the entire body of the bird. Body feathers have a definite curve in the quill, which imparts a certain amount of spring. This makes these feathers suitable for featherbeds, feather pillows, and down blends.

Down is the soft underplumage that geese and ducks grow to keep them warm. Unlike a feather with its stiff quill shaft, a down cluster looks like a dandelion puff, and is very soft. Feathers are flat and two dimensional, and cannot trap air. Down is three dimensional, and can capture thousands of pockets of air, and it's the air that does the insulating. The smaller and more numerous the air pockets can be made, the more efficient is the insulation, as convection currents that carry heat away are eliminated. Down can trap more air for its weight than any other material. Its millions of filaments interlock and overlap to form a layer of still air that keeps warmth in and cold out.