Qualities of Down Comforters

Softness

• How soft your comforter is depends, in part, on its thread count. Thread count is determined by the total number of threads in a square inch of the cover fabric. Higher thread counts result in a softer comforter with a tighter weave that won't leak as much of the filling. Look for fabric that's made from 100-percent cotton or silk, with a thread count between 230 and 380.

Warmth

• Down is a type of plumage that helps to keep geese and ducks warm. It consists of clusters of light, fluffy filaments that grow in all directions and aren't attached to a quill shaft. The clusters create tiny pockets that trap air and body heat when they "loft," or expand and fluff. How well a cluster fluffs depends on its size. Larger clusters provide more warmth. Cluster size is measured by "fill power."

  Fill power is the number of cubic inches that 1 oz. of down occupies. Warmer down has a higher fill power number. A good quality comforter should have a fill power number of 525 to 600. Top-quality comforters have fill power numbers of 700 or more.

  Goose down is the type of down most commonly used, because it's heavier and warmer than duck down. Comforters filled with duck down are considered lower quality, unless the down comes from eider ducks, which is some of the softest and rarest down available -- and also some of the most expensive down. Larger, mature birds produce the warmest down.

Weight

• Fill weight shouldn't be confused with fill power. Fill weight is the weight of the down and feathers used in the comforter. It measures quantity, not quality. Comforters with a higher fill power may use less down and have a lower fill weight.

Construction

• Good-quality down comforters are made with "baffle box" construction, which means that fabric "walls" have been added inside the comforter, between the top and bottom layers. Baffle box construction lets the down fully expand and helps keep the down from shifting around and becoming lumpy. Look for "true baffle box", "closed baffle box" or "end-to-end" baffle construction, which means that the baffle boxes are completely sealed. Down can shift in comforters made with partially open boxes. Sewn-through stitching is a lower cost option that helps to keep the down from shifting by stitching through the comforter from top to bottom.