Originally Posted by
Grandma Mary
What is a sub, or slub? Is it tangles in the spool or knots of thread?
If you look at a piece of thread under a magnifying glass you can see bumps on the thread that prevents it from going into the needle. Some thread have small ones that don't cause a problem but many have large ones. My kids had a microscope and now it is in my sewing room. It is amazing to see the difference in the thread, some very expensive thread is awful looking.