| Feathers,
the principal covering of birds, are of flat, almost two-dimensional
construction. They have a hard, tubular quill shaft from one end to the other. As a 2-D structure, feathers are unable to trap air effectively and therefore have little insulation value. Feathers are strong as a result of a vane center, however, feathers have little softness value. Down is the light, fluffy undercoating of waterfowl, consisting of clusters of filaments growing from central quill points. A Down cluster has a quill point but no quill shaft, so it is far more resilient than a feather.
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 Down
is lighter than a feather, it is three-dimensional rather than
two and therefore Down has more loft or filling power.
When Down is compressed, a good shake is all it needs to make
it bounce right back to its original fluffy loft.
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A single ounce of Down contains thousands of clusters that trap warm, still air to prevent heat loss. What is Fill Power? Fill Power measures the cubic inches one ounce of a given quality of down will occupy. The more cubic inches one ounce occupies, the better the quality of that down. Example: Which will occupy more space (i.e. cubic inches), one ounce of cotton balls or one ounce of salt? The cotton, of course. |
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