I use sheets all of the time for backing. I buy the 200 thread count at Walmart and have not had any problems. If I need a matching color I use dye(not Rit). and even do tie dyeing to make it more fun. Be sure to wash the sheet after dyeing tho so it doesn't bleed. I would rather spend 4.00 on the backing and have more money to buy the top fabrics. I remember my grandmother using anything she could find for quilts and I think we have somehow lost some of the old fashioned ideas that went into quilt making.