I bought a bolt of "Roc-Lon" permanent press muslin that is preshrunk and 100% cotton.......can't remember where I got it but it might have been at JoAnns with a coupon or when I use to have a license from my wholesaler.
over 100+ years ago, muslin was the top of the line of fabric, or so I've heard...tightly woven and used in wedding dresses, etc.