Prism99

I haven't found a good explanation of how to do this on the web; the excellent book that explains it is packed away in a box and I can't remember the author's name.

Only the batting is divided into thirds; the top and backing are left entire. You layer the middle piece of the batting into your quilt as usual, and quilt that section first. This eliminates tons of bulk under the machine arm. Leave several inches on each side of that batting piece free of any quilting.

When done quilting the middle section, pin the top and backing fabrics back away from the batting edge on one side, and attach the side piece of batting to the middle piece of batting. Unpin, layer, and quilt that side section next. Do the other side section the same way.

You start with a large piece of batting cut to the right size for your quilt (with extra inches all around, of course). Instead of layering all 3 full-size pieces, at this point you take just that batting and cut it into 3 sections with a rotary cutter. Don't make this a straight cut; curve your cut back and forth about 6 inches so you end up wth a long, deeply curvy, wavy cut. Save the two side sections (mark each piece so you know which is right side up and top), and layer just the center piece to start quilting. It's a good idea to use a marker to make registration marks at a few points along the cut before separating the pieces, to make lining up these pieces easier later on.

When it comes time to attach a batting side to the center piece of batting, the curving lines will help you make an exact fit so you are re-creating the full size piece of batting exactly as it was. Some people will machine zigzag the two pieces of batting together at this point, but I think it is better to take the time to hand tailor-tack the pieces together. Sharon Schamber shows how to do this stitch in her youtube video on basting a quilt. Once the two pieces of batting fabric have been re-attached, you layer the top and backing fabric over it and proceed with machine quilting that side.

One of the reasons for making the deep curving lines for the cut, aside from matching the batting pieces perfectly, is that the finished quilt won't develop a line where the batting was connected -- from folding, or use. The slight weakness from the cut will be distributed across a wide area.

It's really hard to describe all this adequately in a post! Wish I could find a website with some photos of the process. I'm not sure why more domestic machine quilters don't use this method for large quilts. It reduces bulk when working on that middle section of the quilt, which makes for easier free motion quilting of that area. You don't have so much bulk under the arm of the machine, and you also don't have so much drag and weight to the left of where you are working. You can just roll up the top and backing on each side so it stays pretty much out of the way. And this method doesn't affect the finished appearance of the quilt the way quilt-as-you-go or quilting in 3 separate sections would do.