I know it's against the "rules" of strict quilters, but I love using white cotton sheets, good quality, not more than 200 thread count. I would NOT use sheets if you are going to hand quilt, because they are harder to quilt, but if you intend to machine quilt- go to a discount store like Ross or Marshalls or TJMaxx and see if you can find a white flat sheet. Lots of fabric for the $ too. (I almost always use sheets for quilt backs. Shhhh! Don't tell on me.)