How is the canson rag surface, is it necessary to coat for displaying with out glass?
Like all cotton papers, it isn't as smooth as a wood pulp based paper. Especially in dark areas, a finger nail scratch would show easily. There is a kind of micro nap to these papers. It wouldn't, for example, be good to graze the corner of one print with another.
Premier Print Shield spray (probably the same as Hahnemühle Protective spray, which I use, and Moab Desert Varnish) help with this, but they not as protective as glazing.
I have a botanical specimen print on Hahnemühle German Etching with four light coats of the protective spray. It once was splashed with a little red wine. I was able to remove it with a damp Q-tip.
Brian A