Density refers to how many individual fibers are located in a particular patch of skin. It is usually measured by the square inch or square millimeter. Hair is always the least dense form of fiber, usually presenting with fewer than 500 fibers per square inch. On the complete opposite side of the scale is fur, like Angora rabbit, which is almost always greater than 60,000 fibers per square inch. Then tucked happily in the middle is wool. Wool usually presents with between 500 and 60,000 fibers per square inch.
Density might not seem like it would have an impact on fiber qualities directly, but it certainly does. Density of the fiber is one of the primary determiners of lock structure. Breeds like Merino have dense fleeces averaging 35,500 follicles per square inch and as a result, have very blocky and crimpy lock structures. A breed like Coopworth is closer to 12,000 follicles per square inch and has pointed locks with a more wavy appearance. This difference in fiber density can be attributed to an evolutionary response and human interference.
Many mammals grow hair that helps them survive in a particular environment. Yaks grow a dense undercoat of soft downy fiber to survive frigid winters. Humans continue to breed sheep, alpacas, goats, and other fiber producing animals, often with a focus on increasing fiber density. More fiber also
|Sea otter fur has a density of approximately 800,000 medullated follicles per square inch. The otter has developed this thick coat to keep warm in freezing water in lieu of a layer of blubber. That’s more than 16,000 times more hair than you have on your head!|