Linen is made from the flax plant , same place we get flax seed (health food store) and Linseed oil (art store or Hdwe.) It’s a coarser , stronger fiber than cotton and very rot resistant (thus good for Foamies) Real linen feels stiffer than the cotton substitutes sometimes called linens (beware) ... and bedsheets and table cloths , linen closets, etc. etc. all misnamed . If it feels really soft , it’s probably not Linen, which feels like a well starched fabric .
I have painted on real linen canvas for many years now and still have paintings over 50 years old on linen that looks good as new, whereas the cotton canvas we used are all turned darker and become more fragile (rot) ... we don’t want that on a trailer eh, or a painting meant to last ...
Nice thing is, because it’s so Strong , you can go much Thinner material ... like on the FoamStream where I used an 18 oz. cotton canvas, I could have used a 6 oz. Linen canvas instead, giving the same results ... but it , even thinner, would have been more expensive, unless it’s on sale or you have a good coupon ...
That being said , we sometimes stop by the local Thrift Store , where that always seem to have Linen (real linen ) curtains/drapery for sale cheap ... which might make a good covering , and for a pittance... Yet to be tried , here anyway... another resource to further investigate ...