The finest goose down, Eiderdown, comes from Siberia. It grows on the breasts of the waterfowl, next to the skin underneath the outer layers of feathers and has unusual insulating ability, efficiently trapping body heat without the added weight while it breathes and wicks moisture and perspiration away. When used in a comforter, this keeps your body temperature near a comfortable 98.6 degrees Fahrenheit without a feeling of clamminess.
The most important factor in determining the quality of goose down is the fill power, or the number representing the cubic inches 1 oz. of down fiber occupies. The number commonly ranges from 500 to 600, though higher numbers can be found, which represent higher quality, loftier and more insulating fill powers.
Goose down used in comforters has gone through a very thorough cleaning process beginning with de-dusting. It is then purified with a gentle cleanser in hot water, dried and sorted, which is not only done to eliminate natural odors but also removes allergens. Most people who believe they are allergic to down are actually allergic to the dust and debris that has not been removed from the fill. Well-cleaned goose down is hypoallergenic.
A quality goose down comforter will be constructed with a baffle box design, which features a number of square sections divided by inner walls between the fabric layers of the cover that keep the down from shifting and clumping. This reduces cold spots and better allows the down to retain its loft.
Goose down comforters are best protected with a high thread count cotton cover, holding the down inside. To protect the comforter from oils and dirt, insert it into a duvet cover, which can be made of any fabric to coordinate the decor of your room. It is also easily removed for laundering and will extend the life of your investment.