Funny story (funny now, not then) about using invisible thread in the bobbin the first time I tried it. You know how sometimes when you wind bobbins, if you're not careful, the thread will start winding around the bobbin-winder shaft instead of on the bobbin? Yup. By the time I realized what was happening, I had a bunch of that invisible thread wound around that shaft. It was so tightly wound that I spent a couple of hours cutting and unwrapping thread from the machine. I never tried to use it in the bobbin again.