Smocking stitches are done with regular embroidery thread. On silk dresses use silk thread and on cotton cloth use cotton thread. Longevity: The mixture on the core yarn and spandex coating makes the yarn really long lasting and proof against put on and tear. Denims crafted with SPFL covered yarns https://angelohexof.blog5star.com/32124603/the-greatest-guide-to-double-covered-yarn