Okay, now I've been reading all these responses about using Mom's old wooden spools and serger thread, and Aurifil...
I am a new quilter but have been a garment maker for years. I have TONS of thread from that, plus I bought a "sewing room" from an estate sale and she had a lot of serger thread(to add to mine, too) and some large cotton spools of neutrals, and old poly thread. I started using the gray cotton thread to piece with after going to classes and reading the blog here daily, but can I really use all the other threads for piecing? I machine embroider, too, so I have hundreds of spools in all. It seems silly to buy aurifil although I'm sure it's lovely to sew with and hides well, I just want to make sure what I use will be strong enough, but not too thick it will show!!! I just bought a box of 50 bobbins... I needed this thread a week ago!