Posted by John Fiorillo on September 16, 2000 at 23:39:50:
In Reply to: Long-Term Effects of Repairs posted by Eric Mandelbaum on September 16, 2000 at 21:25:38:
Eric,
You ask an excellent question, and it raises a point I wanted to introduce, but then did not because, as you say, the discussions were getting rather heated (some of it my doing). It did seem to me that a contributor or two implied that immediate positive visible results were sufficient to declare victory over damages to prints. At the risk of seeming to rant about this subject, I’ll provide a long but I hope useful response to your question.
Bleaching or aqueous chemical washes are among the techniques mentioned here or on other sites. My call for professional intervention over do-it-yourself cleaning is based on warnings I have read in various publications. For example, the following might be of some interest:
Margaret Hey: "Paper Bleaching: Its Simple Chemistry and Working Procedures," in: The Paper Conservator, 1977, vol. 2, pp. 10-23.
"Bleaching is the restoration procedure which potentially could do most harm to paper yet it has been the least thoroughly investigated. … The fundamental point on which all the chemistry of bleaching hinges is that every compound has characteristic solution pH values at which it is safe (or conversely, harmful) to cellulose. These conditions are different for every bleaching agent."
With respect to the dangers involved in bleaching, she includes cellulose degradation due to: (a) "immediate scission of the cellulose chain (noticeable weakening of the physical structure), … (b) oxidation of the cellulose chain. This does not necessarily produce an immediate physical weakening but through the introduction of carbonyl groups the cellulose will have an increased tendency to yellow. … In addition the presence of carbonyl groups along the cellulose chain means that the cellulose becomes very susceptible to damage by acids … and also to caustic alkalis" [present in some bleaching solutions].
I may be accused of scare tactics here, but I do not mean to suggest that bleaching can never be done. There are various methods and compounds that will work in limited circumstances, and even some alternate methods that have been tried at least on an experimental basis. See, for example, Keiko M. Keyes, "Alternatives to conventional methods of reducing discolouration in works of art on paper," in: G. Petherbridge (Ed.), ‘Conservation of Library and Archive Materials and the Graphic Arts’, 1987, Butterworths: Institute of Paper Conservation and Society of Archivists). However, what I just quoted above very briefly mentions just a few concerns involving only the paper itself, that is, they do not even cover the complexities of the colorants used on the paper or their potential reactivity with bleaching agents. Even when expertly used, a bleach and subsequent alkaline wash might be safe for the paper but NOT for a particular colorant. Everything should be pretested and then an expert, experienced conservator should make a decision about whether to proceed. In addition, most colors on Japanese prints are fragile, and thus bleaching methods that work on other types of works of art on paper could be disastrous when applied to Japanese prints, especially ukiyo-e.
I, too, have seen the results of bleaching on Japanese prints. A few years ago a charming Kiyomitsu pillar print, c. 1760, was sold at auction with the catalog description "faded but very clean." Well, of course it was "very clean," having been bleached to a ghostly white! It still sold for more than $3,000 to (I suspect) an uniformed bidder. As for your bleached example, I assume the dealer lowered the price because regardless of any potential long-term effects, the fact that the bleaching was obvious made the print less valuable.
The bottom line on bleaching might be oversimplified as follows; If the methodology was correct for the particular paper, its original colorants, and the degradation products marring the appearance of the print, and if the print was buffered properly without leaving any significant byproducts behind, then maybe the print will have some happy years ahead. But if the methods were inappropriate or improperly applied, then long-term, latent effects might indeed manifest themselves. Further treatment at that point might not be possible if the paper matrix has already been harmed enough (e.g., scission of the cellulose chain) to prevent further effective treatment.
As for glue and backing residues, most of the damages would, of course, come from acidic materials. Yet even alkaline (buffering) materials in certain circumstances can pose difficulties. The aforementioned expert conservator K. Keyes cited a case in which a Japanese print was reinforced with alkaline Japanese paper (the thinking, I assume, was that such a paper would provide a buffer against future acidic buildup much like a buffering wash at the end of aqueous discoloration treatment is said to do). Unfortunately, color changes were subsequently observed in some pigments that turned out to be alkaline vulnerable. Thus issues arise about backing papers, discoloration treatments (including standard buffering), and storage mat boards for long-term use. The point here is that an expert should be considering a wealth of technical information, testing everything on the print, relying on extensive experience, and making an informed decision before proceeding with any sort of treatment, mounting, or storage of works of art on paper. Those who have treated their own prints by focusing on the damaged area to the near exclusion of other components and then have witnessed an immediate improvement in appearance may or may not have improved their prints for the long-term. These complexities in print conservation do exist and are not mere arguments to scare off the uninitiated.
John