We have a project where a large portion of the stone wall in the lobby will serve as an art installation (stone will be etched & then sealed). I was wondering if the sealant used (if applied on-site) would need to be compliant. Technically, it is a medium for the artist & not a building construction material--I am thinking of it along the same lines as oil paint (for example). Any thoughts? I saw the post above, but I was wondering if anyone had a specific reference for this issue.