Originally Posted by nanna-up-north
The larger the number, the finer the thread. 100 would be very fine. Size 50 is standand sewing thread. If it is super strong it must be polyester..... try burning a wad of it in an ashtray. If it burns, it's cotton. If it melts, it's poly or some other man-made fiber.
I like to sew my quilts with 100% cotton thread because I've heard that pure polyester is so strong that over time it will cut the cotton fibers in your quilt. When I've used cotton/poly thread I picked something that wasn't 100% poly and haven't had a problem as yet.
I'll be interested in hearing how this thread works for you.
You are too smart. It made a little flame and melted together into a small blob. Didn't all melt of burn just a small bit. Hard part was getting my old matches to light here in humid FL.
Also compared it with some thread I've pulled out of some polyester pillow shams--same thickness, strength and flamability.