Originally Posted by
majormom
Do you use the starch in a spray bottle or do you immerse the backing into the starch? Is that a dumb question? :-/
Actually, I mix up the starch solution in a bowl and apply it to the fabric with a large wall painting brush until the fabric is saturated. I wait just a minute to make sure the fabric has absorbed the starch, then toss it in the dryer and iron with steam (which reactivates the starch). I usually do this before sewing the backing pieces together, but you could do it after the backing is pieced too. It makes the backing so stiff it won't pucker when you machine quilt.
You can use starch even if a quilt has already been sandwiched. Lay it on the floor and mist with spray starch (I used the canned spray starch) several times, allowing each starch layer to dry before adding the next (a fan will speed up drying time). The backing won't be as stiff, but this is often enough to stop puckers. You can also spray starch the top to help prevent puckers on the top when machine quilting (especially useful if your quilting lines will be crossing each other, as in crosshatching).