08/13/2018
Tip of the day (warning: long post): Your stitch tension can affect how much shrinkage you have on your quilt top after longarm quilting is finished. There are other factors too but let's just focus on this one for now.
Do an experiment on a small muslin quilt sandwich. Measure and physically mark two 24 inch squares (or whatever your throat space will allow) on the muslin top.
Set your bobbin case tension at 22 on your TOWA gauge. If you don't have a TOWA gauge, tighten your bobbin case tension until the bobbin case almost lifts off of your palm when doing the palm tension test. Balance your top tension to get a good quality stitch. Now stitch a 1/2 inch crosshatch pattern in the first block without using a ruler or worrying about precise lines. Or just randomly do some swirls and curls in the entire area.
Now, take your bobbin case out and set your bobbin case tension to about 14-16 according to your TOWA gauge. If you don't have a TOWA gauge, loosen your bobbin case tension until your bobbin barely stands up in the palm when doing the palm test for bobbin case tension. Balance your top tension again to get a good quality stitch. Now, once again stitch a relatively tight crosshatch pattern or just some swirls and curls throughout the entire second square.
After your finish your experiment, go back and measure the squares. The top square that you sewed with a tighter stitch should have more shrinkage than the bottom square. In fact, the bottom square may have no shrinkage at all if you did not have your quilt top stretched too tightly between the rollers.
So, you may wonder what is actually happening in the above exercise. With the tighter tension, the thread is being somewhat stretched coming out of the bobbin case and the top tension is also tight so that the top thread is also getting somewhat stretched when it is set correctly to form a uniformly balanced stitch between the top and bottom. After the stitch is made, the thread on both the top and bottom returns to its normal length causing the material in the quilt sandwich to be gathered tightly in the stitch. This gathering of the material into the physical stitch causes quilt top shrinking when looked at it across the entire quilt top. With the lighter tension in both the bobbin case and the top thread, you have less stretching of the threads so less (if any) movement back to normal thread length; this means little if any quilt top shrinkage.
Don't throw away your experiment; donate it to your local animal shelter.
Credit to Karen Dillman Farnsworth for introducing this concept to me.
