I just checked my sulky weekend quilting book. I have a lot of sulky 40 wt.too, that I use for embroidery.And three of the sulky books.I have never used the 40 wt. for quilting. Haven't made that many quilts yet.And always used cotton.This is what the book reads, because of sulky's silky finish and legendary quality it will smoothly glide through a quilt top,batting and backing when stitched by hand or machine.Sulky rayon does not fray, and fuzz or shrink. Color fast, but NOT with chlorine or Optical brighteners. If you go to the sulky site,you might be able to find a chart. I just thought I'd pass this on since I had the book. I have used it in embroidery,on table linen mats,toaster covers,things like that.I would use it for a runner too.For a quilt,I'd have to think about that.Just so many nice threads out there.