I don't know where Faintly Artistic gets her beautiful vintage sheets but I get mine from two sources. Thrift and even consignment stores are a gold mine of 100% cotton sheets. I can see using blends for this project but I keep to all cottons for quilts.
Then there are the 100% cotton sheets that we seem to go through at our house. My dear DIL loves her two sweet dogs and they "sneak" onto their bed when they are at work. Their nails provide me with great cotton scraps on occasion. HaHaHa. I am allergic but I love these two pups! My sweet kids have also provided me with a new grandson, a great sewing studio complete with coffee bar, and a loving, permanent home ; so I am a happy quilting granny!