Why Machine-Washable Wool Needs Protection Against Felting

Untreated wool fibers have microscopic surface scales. Under washing conditions, moisture and mechanical agitation can make neighboring scales interlock, causing felting and a denser, smaller textile. Woolmark describes machine-washable processing as a way to reduce that interlocking, rather than changing the material into a synthetic fiber.

Different technologies smooth or remove scales, reduce friction between fibers, or combine those approaches. The purpose is better dimensional stability and easier domestic care. That does not make every wool garment machine washable: the finished product still needs the appropriate care instructions. The useful distinction is between wool's natural structure and the additional engineering applied to a particular textile.