OPTIM processing stretches wool fibres before they are incorporated into yarn and fabric. When the resulting woven material undergoes wet finishing, fibre recovery helps the construction contract into a tighter arrangement, producing a denser cloth from the engineered starting structure.

OPTIM Processing Tightens Wool Fabric During Finishing

Woolmark describes this route as a way to develop performance through fibre behaviour and fabric construction. The final result depends on how yarn, weave and finishing interact, rather than on treating every ordinary wool fabric as though it already has the same compact structure.