Archival Methods of Treatment for Library Documents
Library of Congress,
Preservation of Paper and Textiles of Historic and Artistic Value II
(Advances in Chemistry Series, no. 193)
Edited by John C. Williams
at the 178th meeting of the American Chemical Society, Washington, D.C.,
September 10-12, 1979
Preserving the great and growing collection of the Library of Congress is a Herculean task. There are numerous techniques available, including silking, lamination, encapsulation, boxing, deacidification, and cold storage. Decisions must be made, often in the face of incomplete evidence, on which treatment(s) to use. What will most extend the life of an artifact? What will the next conservator have to undo that we have done? Every generation of restorers has left problems and created damage that have plagued succeeding generations. Our generations legacy to the future may be better because of better training for conservators, and the effective and growing collaboration between practicing conservators and conservation scientists. We advocate a conservative approach to conservation. Where we cannot restore completely, we often can stop degradation effectively, hoping thereby to transmit the work to our successors unimpaired and receptive to more advanced techniques that may develop in the future.
As a practicing conservator with over twenty-five years experience in book and paper conservation, I view with approbation the increasing number of young people who are choosing this profession. My colleagues and I welcome the opportunity to train them in the important task of preserving our artistic, literary, and scientific heritage. I find the work and interest of conservation scientists extremely helpful.
At the Library of Congress the responsibility for making decisions on the treatment of important, or not so important, documents is a heavy one — decisions on when and how to treat, or when not to treat, or on when to store and how to store. How are we best to use limited 13
14¦ resources of trained personnel and often inadequate budgets? How do we best establish priorities with the custodians of the collections? These are decisions that all conservation staffs are facing.
At the Library of Congress current estimates indicate that for materials presently identified as rare, with permanent research value, complete conservation will require about twelve thousand five hundred man years of work. Other parts of the collections are in equally serious condition. However, archival conservation in a library setting diminishes the role of restoration of individual artifacts in favor of carefully selected actions more immediately directed toward the greatest possible prolongation of useful life — hence our philosophy and practice of "phased" preservation. In practice, useful life may be projected as a thousand years or more for some items, or as little as fifty years for others. Thus, in the broadest sense, conservation comprises methods of buying time, of putting off that inevitable day when organic materials are reduced to dust.
Environmental controls and stabilizing treatments can, of course, slow down decay rates, but the rate will be dependent on the condition of the untreated artifact as well as its original makeup and its inherent ability to withstand use, abuse, and unfavorable environmental conditions.
All materials do not age at the same rate. This fact is important for all of us to appreciate — our scientist colleagues, when designing mass preservation treatments, and the conservators, who are charged with responsibility for recommending and carrying out treatments and housing procedures that need to be specific for each category of library and archive material, in keeping with curatorial and/or institutional policy. Any institution's management policy toward preservation is perhaps the most important element in any effort to arrest decay and preserve the kinds of collections that future generations will wish to enjoy and use for research. Without firm direction or a firm preservation philosophy, precious resources may be wasted, as when too much effort is spent on treating small numbers of individual items at the expense of important large bodies of collections for which preservation measures need to be devised.
In addition to a well defined philosophy, library and archive preservation requires very long range planning. What form might a library or archive repository take in fifty to one hundred years time? Will those patterns have to change? Will growth rates permit a rational, orderly preservation effort, or will they be so large as to stultify efforts to produce meaningful programs?
If we are to come to grips with our present preservation problems, massive efforts must be made to reduce the size of collections on a selective basis, to limit growth rates by stricter evaluations, and above all, to define, plan for, and accept realistic lifespans of usefulness on materials 14
15¦ to be retained in original format. Policies based on the assumption that all materials must be retained indefinitely will ultimately result in sizable parts of those collections becoming unsalvageable because preservation resources have been spread too thin.
This problem of controlling future growth is one of the greatest challenges in this field. Whether or not this generation is capable of facing up to it remains to be seen. Either we face up to it now or convey to the next generation an inheritance greatly diminished by our failure to make the hard choices.
The state of the art for the conservation of large collections of items can be expressed at the Library of Congress in two words: "phased preservation." This entails better housing for collections, better protection for individual items by use of alkaline folders or mats and boxes, or polyester film folders and encapsulations, and better surveying to establish needs for future treatment. Necessary treatments may then be given orders of priority and scheduled for execution in phases over an appropriate period of time.
We must have an appreciation for the problems of our curator colleagues and work in collaboration with them. We hope they in turn will be concerned for and become knowledgeable in matters of preservation. It is not necessary for either curator or conservator to become a scientist, but understanding the concepts, methods, and language of science will help them both not only to work with scientists but also to know how to ask the right kind of questions or define with precision the particular problems they may wish them to investigate. The more precise the definition of the problem, the more likelihood there is that the questions will lead to answers that can be relevant to actual conservation practice.
The library and archive community has been awaiting anxiously the development of viable systems of mass deacidification, hoping that they could be a major breakthrough in conservation. Strengthening systems also have great appeal to those who believe there may be a miracle cure-all down the road. I am afraid, however, that a great number of librarians may be in for a disappointment. Viable systems certainly are needed and a few may be close to realization, especially for papers of reasonable physical strength, but I am not convinced that brittle material ever can be endowed with a long life expectancy. It is well known that there are millions of items in this state now, let alone those that will be reduced to brittleness if they remain in their present environment.
Since Washington summers are known for high temperature and humidity levels, it might be said that the collections at the Library of Congress have suffered from a natural accelerated aging process. The majority of nineteenth and twentieth century books and unbound items that are brittle in the Library of Congress, and no doubt other collections, 15
16¦ became so prior to the gradual installation of general air conditioning, completed in the late 1960s. Since then, the rate of deterioration of all materials is believed to have been slowed.
Thus, the desire for mass deacidification treatment systems must be coupled with the recognition that reduction of temperatures and humidity levels is an equally important and perhaps more effective way of slowing down the rate of deterioration for sensitive material. Just as we have selected areas in libraries for rare book rooms and special storage areas, a modern library should, in my opinion, plan to have large areas for cold storage, not necessarily for general collections, but for collections that are dormant, in low use, but valuable. Many far-sighted librarians, especially Gordon Williams, have recommended such an approach, but curiously little has been done to make it a reality. It would be advantageous if library planners and architects could become more sensitive to factors affecting preservation of collections.
Relationships of Historic Technology to Longevity of Paper
The early western papers produced by the scholar printers, such as Jenson in Venice, in the late fifteenth and early sixteenth centuries in many cases have survived in pristine condition. Some of the factors in the longevity of these papers include the high crystallinity of the cellulose molecules in the fibers produced from retted flax and the use of wooden stampers for beating the fibers, which leads to great strength retention and good fibrillation with maximum opacity and density. In the course of their production, these papers apparently absorbed alkaline salts and magnesium and calcium carbonates, probably from natural stream water and the liming of pulps.
Some of these early papers were sized, at least one Italian paper mill, in Pesche, being known to have used a size made from scrapings of parchment skins (split skeepskins) called "fleshings." The adhesive action of the gelatin would have caused a substantial amount of calcium carbonate to be locked around the fibers. Other beneficial features of the manufacture of these papers were that they had no fillers, were sun-bleached, and had few metallic impurities to hasten serious oxidation.
After the invention of the Hollander beater in the late 1600s, metallic impurities (copper and iron) got into the paper pulp by contact with the metal rotary grinders. This type of beater is blamed also for the accelerated decline of quality in papers because its particular beating action shortened the fibers. Another production change reduced the amounts of alkaline earth carbonates present: new forms of gelatin, made from sinew and muscle, did not possess the natural alkalinity of the by product of the parchment maker.
17One can see evidence throughout fifteenth and sixteenth centuries works of the suspicion that binders had for the new material called paper. Because binders were used to handling vellum-section books, it is perhaps not surprising to see vellum guards used to support the sewing threads in paper-sectioned books. Bookbinders who had produced what we would now call a kind of archival binding, without adhesive in its construction, began to use adhesives in response to increased demand and production. The very strong structures comprising the spines of books gradually began to be reinforced with whole wheat flour paste, later to give way to bookbinding gelatin glues, which have had a disastrous effect on bindings and paper ever since. As reliance on these adhesives grew, the strong sewing structures of earlier centuries unfortunately were retired gradually.
As unbound paper materials became damaged and worn by use or weakened by the deterioration resulting from "improved" methods of manufacture, they have been given restorative treatments representing the entire gamut of binder's know-how. For two or three hundred years now, water-soluble adhesives have been used throughout Europe and this country in the strengthening, mending, lining, or mounting of manuscripts, maps and documents, and records of all sorts. Adhesives have ranged over the years from the traditional parchment size to starch and gelatin; gelatin, glycerin, and alum; or numerous variations of these, right down to present-day synthetic formulations.
The water used in adhesives for restoration may have been impure. Cooking pots may have been made of copper, as was the traditional binder's glue pot, or iron. The resulting presence of significant amounts of metallic impurities has contributed to deterioration of the papers through oxidation, in turn leading to high acidity levels and a breakdown of the cellulose chains. The signs of contaminated pastes are usually brown brush marks, overall browning, brittleness, and so-called foxing marks. With these adhesives, restoration of manuscripts was carried out with a selection of papers according to need: matching, if possible, for inserts; thin and strong for edging; transparent for overlays. Goldbeater's skin was also used. Large maps long have been mounted on woven fabrics of linen or cotton.
By the mid nineteenth century, as the weakened condition of the collections of paper materials in major European and American libraries and archives began to attract increased concern, new strengthening methods were developed. The most significant of these was silking — the application of a silk gauze to both sides of a document. The process seems to have been adopted first at the National Archives of France, 17
18¦ where it is said to have been in use as early as the 1860s. It subsequently appeared almost simultaneously in the United States, where a patent was granted in 1896 to Francis W. R. Emery of Taunton, Massachusetts, for a special process using silk or paper and paraffin, and in Italy where silking came into use first in the Vatican Library[5,6]. The famous St. Gall Conference convened in 1898 by Father Franz Ehrle, Prefect of the Vatican Library, to consider manuscript restoration prob-lems and announce the successful development there of a silking technique, was one of the most significant events in the history of archival preservation in the western world. While no American is recorded attending the meeting, its proceedings profoundly influenced the choice of restoration techniques practiced in succeeding decades in such institutions as the Library of Congress, whose William Berwick (d. 1920) attained and taught a real mastery of the silking technique[8,9].
Silking has been used, with variations, in this country and in Europe until recent times. However, it began to fall into disfavor in many sectors in the 1930s as the research efforts of the National Bureau of Standards and of William J. Barrow publicized the qualities of cellulose acetate as the preferred material for the lamination of documents[10,11]. Equipment for cellulose acetate/tissue lamination according to the Barrow system was installed in the Library of Congress Branch of the G.P.O. in 1947 and 1950, receiving heavy use until about 1971, but silking continued to be carried out through the late 1960s.
It may be interesting to note that William Barrow, who opposed silking because of its "limited life expectancy of twenty to thirty years" found that lamination with cellulose acetate was not archival unless the documents were first bathed in alkaline solutions, leaving an alkaline reserve in the paper. Why, I wonder, did he not use the same rationale for silking? It appears that all silking was applied without prior deacidification or alkaline washing of manuscripts; that concept was a product of our more scientific age. If those procedures had been carried out, it is possible that the silking technique with high quality fabric might have equalled or surpassed the quality of any current method of lamination. Visually, it is superior to cellulose acetate lamination, and its reversibility is far greater.
In the Library of Congress collections one can find good and bad examples of the two systems, silking and cellulose acetate lamination. One can only conclude, therefore, that in addition to adequate treatment of the papers before lamination, the craftsman's manipulative techniques of application, (and, with silking, pressing and drying) are fundamental to truly archival protection.
In 1973, the Library of Congress Preservation Office initiated the use of polyester film encapsulation as a technique for the conservation of maps, manuscripts, posters, and carefully selected works of art on paper.
19This procedure was intended particularly for those paper artifacts that are fragile and brittle. The main reason for this development was the growing body of evidence documenting the continuing (or even increased) degradation associated with the use of adhesives and impregnants. Library holdings of permanent archival or research value urgently needed a type of physical protection that would not contribute to chemical instability or permanently affect their visible appearance in any way and that was instantly reversible. Since that time, polyester film encapsulation now has replaced almost entirely lamination and other support techniques relying on adhesives in this library.
The conservation profession (as differentiated from restoration) is still relatively young, not more than about fifty years old. The four major graduate programs in this country for conservation of art and historic artifacts have had considerable success in training conservators to respond to the needs of individual works of art, with paper and objects conserva¬tion recently moving up to a place of equal importance with paintings. Even so, despite the learning opportunities of internships, there are still not enough experienced practicing conservators who are able to deal with the large issues in conservation. Furthermore, as long as available training continues to be weighted toward the treatment of single rare artifacts, I am afraid that not very many students will be interested enough to specialize in the conservation of library and archival materials, for which a different point of view is needed. It can be very satisfying, of course, to pull out all the stops in treatment of a single item of great value. Recognition by administrators of libraries and archives of the desperate preservation needs of their collections may lead to more training programs with this specialization. When that happens, and I hope it will, let us not forget that a creative, imaginative approach to problems often develops best when it follows on a mastery of craftsmanship obtainable only by years of practical experience.
Conservation differs from restoration in its greater concern for the structural and artistic integrity of both single items and large collections. Throughout past centuries, restoration has often led to unnecessary and, to later generations at least, undesirable alterations in the historic char¬acter of artifacts. Restoration of books and of unbound material was, and often is, an almost totally subjective matter; valuable items have been mistreated, deterioration accelerated, and historical documentation on the original condition of an artifact neither recorded nor preserved. This has been particularly apparent in restoration and rebinding in Europe and America in the past two hundred years. In libraries and archives, prints, drawings, and other works of art on paper, manuscripts and cartographic material have been treated not by specialists with respect for individual problems but by binders of varying degrees of manual skill and often very little sensitivity. Only in the past thirty to 19
20¦ forty years has this situation gradually improved.
In the United States, a greater sophistication reflects many factors: the leadership of the first conservators and conservation scientists of the Fogg Museum of Harvard University, beginning with George L. Stout and Rutherford J. Gettens; a tremendous growth of interest in art history, in studio arts and crafts, and the historic preservation movement; the dedication of the small band of American art on paper conservators and their dissemination of knowledge of oriental paper techniques; and by the international involvement of binders, restorers, conservators, and scientists in the rescue operations for thousands of rare books and documents damaged in the flood in Florence in 1966.
It now can be said that the need for a more scientific approach by conservators has been recognized and that the specialty of library and archival conservation is perceived increasingly as being on the level of painting and museum artifact conservation in value and complexity. The goal that some of us have been striving for since the mid 1960s has come within our reach.
Of course, a purely scientific approach to conservation problems can be unbalanced too. A good conservator's choice of a specific course of treatment should take into account a variety of considerations based on a very liberal background training. He should have considerable knowledge of how previous treatments on related material have succeeded or failed and of the art historical significance of items involved. In formulating decisions, the conservator should know how to extract relevant information from such diverse sources as provenance data, testing procedures, and scientific literature. Last but not least, he should have achieved an advanced level in master craftsmanship so that mind, eye, hand, and heart can coordinate fully, each attribute informing the others in proper balance. Such individuals are very scarce as yet, but treatment decisions by persons with less extensive background can be inappropriate and sometimes damaging.
Professional paper conservators, as a group, try to discourage all "do-it-yourself" or universal treatments by amateurs. Such a position may seem negative and unhelpful to private owners or to custodians responsible for serving materials to readers. Nevertheless, we cannot condone, for instance, the use of pressure-sensitive tapes for mending anything but expendable material: few are safe for use on paper artifacts, without potential for reaction of the adhesive with the chemical components of the paper artifact, and most will skin the surface of the sheet if removed. Since conservators often spend a high proportion of their time attempting to correct previous restoration procedures or arrest the resulting degradation, they try to work closely with curators in sound planning and budgeting for professional treatment, especially for collections of permanent research value.
21Temptation to do-it-yourself, however, is always present; library materials needing repair grow more numerous every day, and at the same time the market offers increasing numbers of tempting proprietary products that are advertised as being of archival quality — as indeed some are. The list includes dry mounting film and tissues, heatset tissues, pressure-sensitive tapes, rag boards (which may be made from cotton and/or wood fiber), storage containers, and nonaqueous deacidification solutions.
Although mending materials are not among them, there are in fact some good, useful products on the market. The intelligent collector or custodian should shop around, ask hard questions, try to avoid being misled, and insist on being supplied with data supporting advertising claims of "archival quality." When in doubt, one should check further with conservation authorities, especially those with experience in independent materials testing, to develop a sound basis on which to defend particular choices.
A hypothetical case history may be useful at this point to demonstrate how a paper conservator comes to a decision on a course of treatment. Let us imagine a lithograph by an important twentieth century artist, printed on poor paper that has become brittle. There are a few stains, the nature of which may or may not be susceptible to nondestructive identification. Analysis of the fiber is made by microscopy and a surface pH reading taken, which confirms a high acidic level and accounts for the embrittlement. The conservator is convinced that the acidity should be neutralized and an alkaline reserve left in the paper substrate to protect it and slow down its rate of deterioration. However, he knows also that these treatments may change the character of both paper support and medium. This is a typical dilemma. Usually, a conservator will decide that the artistic intention is the primary element to conserve. In our hypothetical example, no deacidification is carried out. Attempts may be made to remove or reduce the stains locally in non-design areas. General use of a bleaching solution, a questionable procedure under most circumstances because of the difficulty of its complete removal from the paper, may be considered justifiable because of special circumstances. On the other hand, the paper may be left as it is or it may be washed in quality water to reduce acidity.
Such procedures would be considered to be appropriate, though not necessarily adequate, by most professional conservators. They look forward to a time when all aspects of the preservation needs of an item can be satisfied by safe treatments. So far, conservation scientists have not been able to help with answers for some very serious problems; no research to date, for example, has provided guidelines as to how to prevent slight color changes in paper or media resulting from the application of alkaline solutions to arrest decay of the paper support. 21
22¦ As a consequence of the absence, to date, of scientific assistance with this difficult question, many nineteenth and twentieth century works of art on poor paper are not being deacidified.
Now let us consider the added problems in another hypothetical case history of a color print produced over one hundred years ago. How can the conservator know what changes may have occurred already in the colored design layer? The term "original condition" is used often in art conservation. Is this its condition as the conservator sees it now, as he can prove it to have been earlier, or as he imagines it to have been when first produced? Was any change the result of natural causes or of some earlier treatment? If there is reasonable evidence that natural color changes may have occurred, would treatment slow down these changes, stabilize and return altered colors to original condition, or alter completely their stability, causing dramatic changes in the future? Here again, the conservator is not yet supported by sufficient scientific research. He needs data to demonstrate how treatments designed to arrest degradation in paper supports will affect ultimately any pH-sensitive pigments, dyes, and inks that artists use, and what possible interactions between support and media may be expected. Similar questions exist with regard to unaltered retention of the image in manuscript materials.
Deacidification: How and When to Use It
Deacidification is one of the most controversial subjects presently confronting paper and book conservators. Certain facts are well established: much research into paper deterioration leaves no question of the benefits of reducing or removing harmful acidity by the use of alkaline earth carbonate solutions, particularly when treatment leaves at least one percent alkaline salt in the paper. Paper permanence definitely is improved by deacidification and this is not part of the controversy. What is controversial is its use in the face of unpredictable reactions to alkaline treatments. It is possible that pH-sensitive inks, dyes, and pigments and/or paper characteristics may undergo change in visual effects, and for this reason it can happen that, of two conservators consulted for the same material, one might recommend for and one against such a treatment. Furthermore, there might be enough rationale for each recommendation that both might be considered valid. In the final analysis, however, it must be the value of the treatment as conservation that settles the question. Avoiding a treatment is not necessarily sound conservation sense. Using a treatment on the basis that it is the best we can do in the light of current thinking can be equally unsound. We must hope, therefore, that we can encourage conservation scientists to look into the problem for us, but since it can be virtually impossible to limit examples to a narrow field of testing, it will be a particularly difficult undertaking.
1. "A National Preservation Program," presented at Conf. Libr. Congr. Preserv. Off., Washington, D.C., 1976.
3. Marwick, Claire S., M.A. Thesis, The American Univ., Washington, D.C., 1964.
4. Ibid., p. 161.
5. Francis W. R. Emery U.S. Patent 561 503, 1896.
6. Nicholson, E. W. B. "Report to the Curators of the Bodleian Library on the Conference held at St. Gallen, Sept. 30 and Oct. 1, 1898, upon the preservation and repair of old manuscripts," unpublished data.
8. Marwick, Claire S., M.A. Thesis, The American Univ., Washington, D.C., 1964.
9. Berwick, William. "The Repairing and Binding of Archives," Am. Hist. Assoc. Annual Report, pp. 154-161.
10. Wilson, William K., Forshee, B. W. "Preservation of Documents by Lamination"; Natl. Bur. Stand. Monogr. 5, Washington, D.C., 1959.
11. Poole, Frazer G. 'William James Barrow," Libr. Conserv. 1978.
12. Barrow, William J. "Deacidification and Lamination of Deteriorated Docu- ments, 1938-1963, Am. Arch. 1965, 28(2), 285.
13. "Polyester Film Encapsulation"; U.S. Libr. Congr. Preserv. Off.: Washington, D.C., 1980.
December 4, 1979.
(Advances in Chemistry Series, no. 193), edited by John C. Williams, pp. 13-23. Washington, D.C.: American Chemical Society, 1981.