Same thing with really old thread....I mean, REALLY OLD, like from the 1970s. I had a box of old thread from my DH's mom's stuff, and I tried sewing with several different colors....not good!! Most of it was really kinda brittle and wouldn't lay into the fabric well. So I test sewed a bunch of it and had to throw most of it away. some of it felt so stiff I didn't want to put it in the bobbin.