I love string quilts, and scrappy quilts of any kind. I've made two string quilts, one was on a muslin foundation, no batting and backed with a heavy flannel. It is quite warm, and I actually like the weight of it. The other was done with an intentional strip of black across the center of a square of paper. I used doodle pads from the dollar store that had been cut to the largest square possible from the page, and reduced stitch length. When the blocks were done, I removed paper foundation. Bonnie Hunter (quiltville.com) uses string piecing in many of her quilts, she uses pages from phone books as the foundation for the blocks.