I have carried out a little bit of research about whether buffered or unbuffered interleaving paper should be used for proper long term conservation of cotton rag pigment prints and contrary to usual, the advice given on the forum (searching through the last few years’ posts) seems to contradict my findings. Even more interestingly the consensus on the forum seems to be quite consistent, which made me think that I might be missing something. Hopefully this post will see some interesting contribution from those who are more knowledgeable about conservation.
To provide a starting point I will summarize both what seems to be the consensus on the forum over the years, and what I found on the net.
Forum consensus: “unbuffered”
This came from posts referencing a conservator from the Baltimore Museum of Art (post by Scott Wald); Epson email support regarding Exhibition Fiber (post by LynnNoah); and quite a few others which didn’t mention their source so I would catalogue those as (based on experience).
Archivalmethods: “buffered”
This is from their site: “Some suppliers of archival products are providing confusing information about the use of un-buffered boards and papers with photographic materials. Black-white and color photography (both conventional and digital output) should have mounts or enclosures made from buffered paper. This is the recommendation from the latest ISO document 18902, “Photographic Films, Papers Filing Enclosures”. The only items that need matting or storage in un-buffered papers are cyanotypes (architectural blue prints) and protein based textiles. ISO18902 is available at
www.ansi.org.”
Gaylord: “buffered” (given that cotton rag is a cellulose fiber rather than animal protein...)
This is from their site: “Cellulose fibers such as cotton, flax, linen and jute, as well plant-based specimens, can be stored in buffered material. Storing cellulose artifacts in buffered materials will protect against migrant acidity from the artifacts.
Any artifacts that contain animal proteins are best stored in unbuffered material. Protein-based materials include wool and silk, as well as animal-based natural history collections, leather-bound books, and textile details such as pearls. Also, many archivists prefer to store albumen prints and cyanotypes in unbuffered material.“
While I have cited only these two suppliers, the gist seems to be the same (that is, use buffered for cotton based and photographic prints in general). Based on this information, usually I would go for “buffered” without hesitation, especially considering than Hahnemuhle Photo Rag is “calcium carbonate buffered” (according to the specs sheet) which might make it even a better candidate (my guess) but the fact that over the years there were several posts advising to use unbuffered material for pigment prints and "none" about buffered made me think this might be an interesting post to start.
As mentioned, hopefully this post will see some interesting contribution from those who are more knowledgeable about conservation.