Woolmark describes a Merino fabric made from temporarily stretched fibres that contract during wet finishing. This contraction packs warp and weft tightly together, reducing air permeability and increasing resistance to rain. The protective effect comes from the dense cloth structure rather than a separate membrane in the described construction.

Dense Merino Weaving Reduces Air Passage Without a Separate Membrane

Water resistance and complete waterproof-garment performance remain different claims. Seams, design and exposure conditions still matter in outdoor use. The example is valuable because it shows how fibre preparation and weave density can alter weather behaviour while the main material remains pure wool.