Downs wools have great elasticity and so were previously used as the main fibre within wool hosiery yarns. In old wool classing standards, downs wools were actually classified as ‘hosiery types’ for this reason. This type of wool has a relatively coarse fibre thickness, which means it is better suited to being inside of fabric such as a quilt cover, as opposed to coming in direct contact with a person’s skin. Softer wools like Merino make excellent clothing, but do not have the ‘sponginess’ required to withstand a human being lying on top of it.
Dr. Swan’s research shows resistance to compressional force (E.G. how much a carpet can stand up to footsteps upon it) is a mathematical function of fibre diameter (thickness) and fibre crimp curvature. This means thick, tightly crimped fibres such as downs wool produce woolen structures (For example, yarns, carpets, and fibre mats like quilts), which are thicker, hold more air, and are harder to compress.
By contrast, thin, nearly straight fibres such as Optim wool or SRS fine wools produce thin, flexible, easily compressed and creased woolen structures. The traditional Italian recipe for fine wovens is: Fine diameter + A lot of fine crimp waves = Soft to touch, yet holds its shape (drape), and doesn’t crease too easily.