Originally Posted by
Scissor Queen
Bottom line is intended for embroidery. When you're doing machine embroidery and have a thread dense design you don't want the thread so thick on the back side.
I personally don't see much point to using it to piece with. Sure it's finer and you get more on a bobbin but at the same time you've got two different threads in your seam and one may cut the other over time.
I use Bottom Line in the bobbin AND in the top when I'm piecing. It cuts down on the bulk in the seam. I've also used it in the longarm (top and bottom) when I want to do a lot of backtracking, or don't want the thread to show much.
I realize that Superior recommends their (more expensive) 50 weight cotton thread for piecing, but I have never had any problem with the thread melting, and I do use a hot iron.