Archived posting to the Leica Users Group, 2012/05/02
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Cross-posted from Archives and Archivists list: This may be of interest to people who preserve prints. The answer below, is pretty interesting. We have a large photograph collection, and are currently looking for appropriate storage materials to house them. I have heard conflicting opinions about the effects of buffered archival materials on photographs, and I was wondering if anyone had any experience with this. Are buffered materials generally appropriate to store most photos? Is it better to purchase unbuffered materials just to be safe? I am noticing that there are not many unbuffered options available, and that they are generally more expensive. Jennifer Robinson Collections Assistant Newport Historical Society 82 Touro Street Newport, RI 02840 ---------- Forwarded message ---------- From: D NISHIMURA <dwnpph at rit.edu> Date: Wed, May 2, 2012 at 4:37 PM Subject: RE: [archives] Buffered vs. Unbuffered To: "Archives & Archivists (A&A) List" <archives at forums.archivists.org> Let met start by saying that the ISO standards recommend using buffered enclosures for all photographs. Where this has raised concern has been primarily with regard to the storage of chromogenic color photographs and cyanotypes (or true blueprints). The committee recognized that most photographs don't care one way or the other, but it was thought that buffered enclosures would be better since the modern world is polluted with so many acidic gases and even protecting the enclosure fro acid damage (acid-catalyzed hydrolysis) would help the enclosed the photograph by allowing the enclosure to provide physical protection as long as possible. Pre-mid-1970s chromogenic color photographs were acid stabilized (so after the final wash, the photographs went into a slightly acidic stabilizing bath) because the dyes were more stable in an acidic environment. In the mid-1970s, the chemistry of chromogenic color went through a significant upgrade and photographs were stabilized in a bath that actually caused a one-way reaction to occur so the stabilization process from this time became more or less permanent. So concern was raised about whether the enclosures would "undo" the temporary stabilization afforded by low pH. It's important to understand that the idea of an alkaline "buffer" in paper is actually an alkali reserve. If we add something soluble, that will react with acids, then we've simply altered the pH of the paper and there's no reserve. To make an alkali reserve then, we need to add something that will react with acids, but that is relatively insoluble and in that way, it isn't just altering the pH of the paper. Typically low solubility metal oxides, metal hydroxides, or carbonates are used and the most common carbonate in use is calcium carbonate (chalk). It has such a low solubility that one liter of water (about a quart) at 77 degrees F will dissolve about 0.015 grams of calcium carbonate. The absolute water content of paper is really pretty small so the amount of calcium carbonate that will dissolve and be mobile is almost non-existent. In theory we don't worry about migration of calcium carbonate out of the paper and into a sensitive photograph. Eventually the standards committee decided that once the photograph was processed, the owner really had very little control over what pH the photograph was at and post-mid-1970s color photographs wouldn't care anyway so they decided to allow color photographs to be stored in buffered enclosures. And that's how things stand right now. A similar view was taken for cyanotypes and even Dr. Michael Ware, a retired inorganic chemist who is an recognized expert in the chemistry of iron-based photography, said, "Calcium carbonate only poses a clear threat to cyanotypes when in direct contact with the image; it has little ability to migrate through cellulose, so the dangers of chalk-buffered enclosures may have been somewhat overstated." However, knowing that the field normally takes a conservative approach to matters that might affect the stability of archived materials, he goes on to say, "It would, however, be prudent to continue the use of unbuffered materials for the wrapping of cyanotypes." In the interests of sorting this out for the standards, IPI looked at this problem in more detail and I'll be presenting the results next week at a meeting. However, we were surprised to find that commercial unbuffered paper as well as plain lab filter paper also caused cyanotypes to fade and turn yellow. In fact the only test "enclosure" that didn't was some lab filter paper that we treated with hydrochloric acid (and dried) to produce a paper with a pH of 3.2 or 3.2. The problem is that neither the support paper for the print nor the enclosure will survive very well at this pH, but we don't know how much higher we can safely go before the image suffers. (Although we know that the upper limit is less than pH 7.) So you're stuck between the devil and deep blue sea. No matter what you do, it will be wrong. Anyway, as a result, we now think that we may have to look at color and albumen prints in more detail. The whole albumen print question came out of the previous incarnation of this lab. Director, James Reilly started the Photographic Preservation Laboratory here at RIT in the late 1970s that turned into IPI. Anyway, during the 1970s, he was looking at the yellowing of albumen prints and observed that a test enclosure made from Permalife paper (no relation to the current product by that name and not even made by the same mill) caused severe yellowing of albumen test prints and was advertised as having a pH of 8.6. Chemically, Reilly demonstrated that part of the yellowing problem involved the Maillard reaction. The sugar-protein browning reaction that is responsible for much of the complex flavors that are found in cooked food (as well as the browning of meringues.) This well studied reaction occurs more readily under alkaline conditions so in his published research paper, he questioned whether the buffering in his test enclosure might have been a significant factor and perhaps albumen should be stored in unbuffered enclosures. This led to everyone saying that albumen had to be stored in unbuffered enclosures. However, we subsequently discovered that the test enclosures donated by an institution to us for enclosure experiments were loaded with lignin and very aggressive against all photographs. So we publically stated that Reilly's conjectures were probably wrong. More recently, the cyanotype experiment led us to wonder if there was an effect of the buffering on albumen as there was on cyanotype's Prussian blue pigment, but that the effect was masked by all of the lignin that was also present. So we may have to revisit the albumen and possibly the color question (although the color question may be impossible to answer at this late date since there's no way to get freshly made test prints using the old materials and processing chemistry without raising questions about the effects of age on the resultant test prints.) To add to the complexity of the problem, let me add one more thing that I may have already talked about on this list and that's how buffering works. The buffered paper contains discrete particles of a metal oxide, (low solubility) hydroxide, or carbonate to react with acids. We did some experiments a few years ago during two separate projects. In one case, buffered paper envelopes were fumed in an atmosphere of nitrogen oxides at 50% RH. In the other case, buffered enclosure were used in sealed bags with badly deteriorating cellulose acetate film so these enclosures were effectively fumed in an environment (at 50% RH) of acetic acid. The envelopes were subsequently tested and we were a bit surprised to find that both high acidity and high buffer content were co-existing in the fumed enclosures. I realized that the buffer particles have no power to attract acid molecules so reaction between the acid molecules and the buffer was strictly dependent on random collision between the molecule and the particle during what is technically a stochastic process, more commonly called a drunkard's walk by the gas molecule (the only mobile species). The term comes from the idea that if the movement of the molecule was viewed as a series of small steps, the direction of each step is independent of the previous steps. So the acid molecule randomly meanders through the paper and there are plenty of paths through the paper that don't meet a particle of the buffering agent. My colleague laughed and called it "lazy dad." His analogy is that lazy dad is sitting on the couch watching the game and he doesn't want to be disturbed. Meanwhile the kids are running wild through the house -- around and around. (Lazy) dad isn't going to get up to do anything so the only time that he might "react" is if a child happens to run close enough to him that he can scoop the child up (without having to move from his spot on the couch) and tell the child to knock it off. Dad is the buffer particle and the kids are the acid molecules. I don't recall that kids in that condition really think about where they're going so direction is pretty random (probably why so many accidents). So we started wondering if buffered enclosures really performed as advertised or not. So this is the current state of knowledge from which to make an informed choice. This kind of research project is too small for the funding agencies to be interested in so we have to do them on our own dime and this is the sort of thing that "profits" from product sales go into. Good luck. -Doug Douglas Nishimura Image Permanence Institute Rochester Institute of Technology -----Original Message----- From: Stacie M. Parillo [mailto:stacieparillo at gmail.com] Sent: Wednesday, May 02, 2012 4:22 PM To: Archives & Archivists (A&A) List Subject: [archives] Buffered vs. Unbuffered We have a large photograph collection, and are currently looking for appropriate storage materials to house them. I have heard conflicting opinions about the effects of buffered archival materials on photographs, and I was wondering if anyone had any experience with this. Are buffered materials generally appropriate to store most photos? Is it better to purchase unbuffered materials just to be safe? I am noticing that there are not many unbuffered options available, and that they are generally more expensive. Jennifer Robinson Collections Assistant Newport Historical Society 82 Touro Street Newport, RI 02840 o-o-o-o-o-o-o-o-o-o The ARCHIVES & ARCHIVISTS (A&A) LIST is sponsored by the Society of American Archivists (SAA). The opinions expressed on the A&A List do not necessarily represent those of SAA and are not endorsed by the Society. To post to the list, send messages to archives at forums.archivists.org. To unsubscribe or to modify your subscription settings, log in at: http://www.archivists.org/listservs/change.asp To read the list archives: September 2006 to Present: http://forums.archivists.org/read/?forum=archives April 1993 to September 2006: http://listserv.muohio.edu/archives/archives.html To view the A&A List Terms of Participation, visit: http://www.archivists.org/listservs/arch_listserv_terms.asp A&A List Coordinator: Meghan Petersen mpetersen at archivists.org o-o-o-o-o-o-o-o-o-o The ARCHIVES & ARCHIVISTS (A&A) LIST is sponsored by the Society of American Archivists (SAA). The opinions expressed on the A&A List do not necessarily represent those of SAA and are not endorsed by the Society. To post to the list, send messages to archives at forums.archivists.org. 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