At nearly twice the strength of rayon thread, Isacord thread is the smoothest running and most reliable thread produced. ISACORD is a polyester continuous thread that has a comparable shine to a rayon embroidery thread. This is obtained through a special cross-section modified fiber. Isacord has been engineered from the finest raw materials to provide just the right amount of elasticity to allow for high speed running without looping or puckering while virtually eliminating thread breaks.
ISACORD is wash, boil, and lightfast and also has a high resistance to chlorine and abrasion. Therefore, ISACORD is the ideal thread used for extreme treated textiles, e.g. work wear, sportswear, jeans, catering wear, and leather. Isacord can be washed with chlorine bleach or stonewashed without any problems.
This 40 wt. thread is thin, making it an excellent choice for free motion quilting designs that require a lot of travel stitching. Isacord is also very strong and able to take the high speed and intensity of machine quilting and embroidery.
Many famous quilters recommend Isacord thread for machine quilting for its strength and glide during long arm quilting. The thread will never break through the fabric, even on quilts that have been washed multiple times.
What was true then is not true now. You CAN use high quality polyester threads on your quilts. The trick is to always use high quality materials because great thread + great fabric = excellent project.