Experimentation in this area was not fun. That doesn't mean I have given up; it just means that using different threads is now deemed well out of my comfort zone for now.
This table runner is the first free-motion quilting I've done with my new Janome DC2014 sewing machine. I have mixed reviews, but not about the machine. I love it! Despite it being so similar to my 30-year old model, there was still a learning curve. There are two new features on this machine that I didn't have before. 1) stitch speed and 2) needle up/down
Both were useful, but the needle up/down was a breath of fresh air. It was so nice not to have to grab and turn the wheel every time I stopped and started.
Because this project had a white backing fabric, determined by what I had on hand, I wanted to quilt the center star in a gray 40wt. Floriani thread and everything else in white 40 wt. Isacord thread. I decided to thread the need with the gray and put white in the bobbin. Once I finally got the tension right, so that little if any of the gray showed through on the back, I began quilting. It was nightmarish. My machine did not like what I was doing. I re-threaded, changed needles, re-adjusted tension, and most of all, picked out lots of stitches. I limped through it the best I could with minimal gray loops on the back.
If anyone has any tips about using different threads in a domestic machine, please comment. I'd love to hear them.