Originally Posted by
Krystyna
.................but the seam ends up looking like a Frankenstein scar (too tight) or all bunchy with giant stitches..............
Now there's my morning smile
... frankenstein scar!
Basically you just have to catch the two sides together, so open up your width as wide as it can be and lengthen out the stitch. It's a great time to use up ends of thread (bobbins and spools) as it will be buried in a quilt later! I don't worry about colours either, as I tend to use my patched batts in darker quilts, just in case the seaming should show through on a lighter coloured fabric.
When I am joining pieces, I make a fresh edge cut, on any angle to maximize the batting that will stay, and minimize the trim portions. Likewise a fresh cut on the piece I am adding. Or you can overlay the two, and cut through both at the same time, and you know for sure their lines will match.
Angled lines are actually better than all straights at 90°, as that way it will have your joins running on angles and less apt for anything to show through. Plus it helps avoid being right under a seamline of your quilt where you may be doing SITD or running down a section where you may have no quilting. With the angles, it is more likely to get quilted on top of, which will help stabilize the joins.
Some of my joined pieces are pretty small. Some are trimmings of the excess when I sandwich a quilt, and some may be a bit bigger but smaller than anything that I can see me using for a runner, etc.
I keep a patched batting WIP at the cutting table. As I have extras, I add on, instead of making it a major project later on. With it are some of the trimmings that don't get into the patchwork, for when I need narrow pieces for bag handles, or when I am doing a small test sandwich.