Acceptable types of papers for painting

​This proposal entails both chemical and physical issues. Chemically, plywood must be knot free, to limit lignin emissions and hardwood is a poor choice, since it really is just compressed bark and thus, a high lignin source. Dibond, D-lite, Alumalite, or Pro-lite, are all better options as support layers, since each lacks emissions chemistry. If a paper based board is used, it will be chemically safe, whether it is rag or alpha cellulose, but whatever materials comprises the substrate, counter mounting is a wise step, since paper boards can warp Dibond and may warp hard board and ply wood, if they are not thick enough. To keep things simple, acrylic can be used to mount the paper to the substrate, but its poor initial tack must be factored in.
Hugh Phibbs

Assuming the artist is handling the mounting procedure, it’s less risky to create the panel first and execute the painting on the paper once it’s already been mounted.

I’d like opinions from the other Moderators on this notion: If it’s absolutely necessary to execute the art on loose paper and mount the finished work in-studio, it seems to me that one could prepare panels in advance by mounting paper to front and back, and subsequently adhere art to the paper face. I believe this would be simpler and less risky for the artwork, because pasting paper to paper would require a smaller amount of adhesive, and would enable the artist to use a broader range of glues/pastes/films. Plus, the artist would know in advance whether the bond between panel and paper was free from defects before the art was in place.

​Matthew, I would tend to agree that your suggested method sounds 1) more easily reversible in the future should that be desired, and 2) easier to ensure that the secondary support was free of defects before adhering the artwork.  The method you’re describing sounds similar to lining artwork with a karibari board, actually.

The difference between cotton fibers and high alpha cellulose in terms of preservation is likely more of an issue of strength and dimensional stability due to the longer fibers of cotton (in some ways this is a presumption because the fiber length of cotton used for papers can vary from full fiber length to short chopped fibers).
If the paper receives substantial a layer(s) of good quality acrylic dispersion ground, the ground is providing a good deal of the rigidity and strength. If this is then mounted to an actual rigid support, I am not sure that there would be a real qualitative difference between cotton and high alpha cellulose papers (of equal weight) in terms of preservation issues.

​High alpha cellulose paper and cotton rag paper are made with different plant fibers, i.e. alpha cellulose paper is generally wood pulp that is chemically treated during manufacture, while rag paper is generally cotton.  Rag paper also has a high alpha cellulose content.  As Brian said, both are high-quality and it may just be a matter of which you prefer.