Wool fibers are hydrophilic, meaning they readily absorb moisture, but are not hollow. Wool can absorb moisture almost one-third of its own weight.[4] Wool absorbs sound like many other fabrics. It is generally a creamy white color, although some breeds of sheep produce natural colors, such as black, brown, silver, and random mixes.

Wool ignites at a higher temperature than cotton and some synthetic fibers. It has a lower rate of flame spread, a lower rate of heat release, a lower heat of combustion, and does not melt or drip;[5] it forms a char which is insulating and self-extinguishing, and it contributes less to toxic gases and smoke