From what I remember from my quilting days, the salt and vinegar method worked when most dyes used salt during the dye process on natural fabrics. Nowadays there a lot more dyes using different chemicals on non-natural fabrics instead so it may, or may not, work. I can't speak from personal experience but many quilters suggest checking out either Re-tayne or Rit Dye Fixative, which are supposed to be better for modern dyes. Just a thought.