stretch yarn

Stretch yarn is a synthetic yarn designed to stretch under tension and return to its original shape when released. This is achieved through a process of tightly twisting continuous-filament synthetic yarns, heat-setting them, and then untwisting them. This creates a spiral crimp that gives the yarn a springy quality.12

While bulk is added during this process, a high degree of twist is necessary to ensure the yarn possesses both bulk and stretch. The most common material used for highly elastic synthetic fibers like those in stretch yarn is spandex, a type of polyurethane. Often, spandex is used as the core of a yarn, covered by a non-stretch fiber made from natural or synthetic materials, to avoid a rubbery feel in the final fabric.2