550 Goose Down
The basic concept:
The higher the fill power, the better insulating the product.
This may seem like a simple concept, but there's much more to down and fill power than feathers and warmth. Even a basic understanding of the properties of this top-notch natural insulator will help make your next down purchase an educated decision.
What is down?
The layer of soft, fine, fluffy feathers under the outer feathers of adult geese, ducks and other waterfowl.
What is fill power?
A measurement of the loft or "fluffiness" of down based on the amount of space one ounce of down occupies. Fill power is not directly related to warmth, but rather the warmth-to-weight ratio.
For instance, two products with different fill powers may offer the same degree of warmth. But the higher-fill-power product will be more efficient, meaning it will weigh less than the product with lower fill power. A lower-fill-power product requires more down to provide equal insulation.
Higher fill powers are best used for the most active applications, when weight and packability are significant factors.
How does down insulate?
Down of all fill powers traps pockets of air that warm and provide insulation. Dense, lower-quality feathers compress more than finer, more fluffy ones. So it takes a greater, heavier amount of lower-quality down to contain the same amount of air as higher-quality down will trap.
Goose down has a supremely high loft and fill power, which ensures superior insulation and volume retention after compression.
How is fill power measured?
In a clear plastic cylinder, a weighted piston settles upon one ounce of down. The volume, measured in cubic inches, occupied by this partially compressed down determines the fill-power measurement.
The higher the loft, the more cubic inches the down occupies. And the higher the fill power, the more "dead" air the down will trap to keep you warm.
Are there down alternatives?
Synthetic insulation, made mostly of polyester fibers, mimics the loft and warmth-trapping properties of natural down. Though the pros and cons of quick-drying synthetic alternatives and long-lasting natural down are widely debated among outdoor enthusiasts.
While authentic down is widely regarded as the superior insulator, synthetic down is less expensive and requires less maintenance. Most notably, in wet conditions, synthetic alternatives provide reliable insulation and are preferred to slow-drying natural down, which loses its insulating power when wet.
How long will down last?
When cared for properly, high-quality down products will provide reliable warmth for decades.
What are the care guidelines for down?
It's best to follow manufacturer recommendations regarding the care of down. Per the care instructions, many down products can be washed and dry-cleaned, but it is important to air them out before the next use.
Storage guidelines are also important. While down products can be compressed for short lengths of time, they should not be compressed for long-term storage. Also, they should be stored in a breathable (non-plastic) bag and shaken out before the next use to allow the down to loft to its original condition.
Why do down products have wide price variations?
Many factors affect the quality, and therefore, the price of down-filled products. An inexpensive down product may be filled with immature down or a high percentage of outer feathers, both of which will provide insufficient warmth and durability. A quality down product will be more expensive, but will also last much longer than any bargain piece.