Although satins are heavier in texture than twills, the principal characteristic of the satin weave is its smoothness, which is achieved at the cost of strength. The smooth surface of the satin weave is produced by passing the warp yarns over a number of filling yarns, keeping the interlacing to a minimum. The reflection of light by the exposed yarns gives the satin weave its sheen. In a filling satin, the filling yarns are passed over a succession of warp yarns. Because the filling yarns are weaker than the warp, satin weaves are subject to more abrasion but are popular, nevertheless, for their beauty. The best-known satin weaves are the crepe satin, peau de soie, sateen, and damasks. The word satin is derived from the name of the Chinese seaport Chüanchow, formerly called Zaytun, from which this type of fabric was first exported in the Middle Ages.