Most serger thread is polyester not cotton. I think the main thing is to make sure what kind of thread is on that large spool. Coming from someone who embroideries, serges, sewes, etc, a lot of times threads can be used for things they weren't made for. I use serger thread for embroidery. When I made Free Standing Lace Easter baskets and even tiaras for the grandkids and knew they wouldn't last long, I didn't want to use my more expensive rayon thread, I used serger thread. I had to slow it down, double up on the stabilizer and use a bigger needle but they turned out great. Take some fabric, test a square doing FMQ and iron it wash it, see how it looks. Then decide