you need to *market* it as 'bed-sheets'
many quilters will not use sheets for quilting- the weave is tighter and it is much more difficult to stitch through-
the tags on the sheets should contain fiber content- will say 100% cotton or polyester or what ever combination of fibers are in the sheets.
you can do a burn test on an edge-
cotton will (flame) make ash and still have a soft edge- poly (or other synthetic fiber) will melt- leaving a hard edge.
when (quilters) do use bed sheets they are used as a backing- so fq's and 4" squares would be a waste...only whole sheets are generally used
quilting cottons are normally about 60 thread count-----sheets generally start at about 200 thread count.