Paper deacidification

Santucci, L. "Paper Deacidification Procedures and Their Effects, Les... 

Smith, R. D. "Paper Deacidification A Preliminary Report, Libr. Q. 

As acid catalyzed hydrolysis of cellulose is responsible for up to 90% of paper s loss of permanence, researchers have concentrated on deacidification as the primary solution to the impermanence of modern papers. Paper deacidification involves introduction of a strong base to convert acid spedes to their corresponding neutral salts, and the establishment of a neutral buffer to protect the paper against future acidcatalyzed damage. The first recorded attempt to neutralize paper was by Arthur Church at the Victoria and Albert Museum in London who, in 1891, advocated the immersion of paper in a methanolic solution of barium hydroxide [8]. 

The need for paper deacidification is enormous. It is reckoned that between 70% and 80% of the Hbrary and archive collections consist of add paper and are therefore exposed to a dynamic deterioration process. The reaction is self-accelerating because the add deterioration is an autocatalytic process. This means that in the course of the deterioration process more and more acids are produced. The acids in the paper can be neutralized and an alkaline reserve can be deposited. With that the acid conditioned deterioration reaction in paper can be stopped effectively but caimot be cancelled. If the deterioration is too far advanced, more complex preser-... 

D. Mihram, Paper Deacidification A Bibliographic Survey Part I, Restaurator 1986, 7 81-98. 

Fire retardant cigarette paper is produced by impregnation of cigarette wifli solution of fire retardant. Solvent includes water, ethanol, ethyl acetate, aqueous ammonia, or their mixture. Isopropyl alcohol is used for paper deacidification." Anode electrode paper is produce by application of titania-graphene dispersed in solvent... 

Sulfite paper has a relatively short life span, since residual acid will continue to hydrolyze the cellulose and cause embrittlement. Further sources of acid include aluminum sulfate (which is added together with resin to suppress bleeding or feathering of ink into the paper) and S02 and NO from the atmosphere. Much of the world s library collections and archives will soon be lost as the paper crumbles. Various deacidification treatments (e.g., with ammonia, morpholine, cyclohexylamine carbamate, or diethyl-zinc) have been proposed and tried, but at best they can only halt the process of embrittlement and cannot reverse it.14 With the move to kraft pulping, alkaline peroxide bleaching, and increasing use of precipitated calcium carbonate as a filler, the high quality papers produced today are intrinsically acid free and should also resist subsequent acidification by S02-polluted air fairly well. 

Before embarking on any discussion on mass deacidification, the history and development of paper making and causes that lead to deterioration of modern paper are reviewed. 

If acid is present in paper, hydrolysis of cellulose fibers would be inevitable. Hence the removal of acid from paper is imperative. The first attempt to stabilize paper by a deacidification treatment was undertaken by Sir Arthur Church in 1891 using a solution of barium hydroxide in methanol to deacidify the backing of Raphael cartoons. 

Considerable research is being devoted to improve existing techniques, to accelerate the deacidification process, render it applicable for the treatment of bound volumes and reduce the cost of operations. Nonaqueous deacidification has been improved in the past ten years and has reached commercial success. The new process is conducted by introducing "liquified gas" into a chamber containing books. Once the acid ions in the paper have been neutralized, the "gas" is pumped out of the compression chamber and returned to a storage tank. The books can then be dried and return to the shelves. Since a nonaqueous deacidification process does not require books to be unbound as does an aqueous process, its development dramatically reduced the cost of operation. 

Magnesium methoxide has been found to be a very effective neutralizer. However, on a damp day or with a damp paper, the solution tends to precipitate prematurely and leave surface deposits on the treated paper. Methyl magnesium carbonate is also effective but much less sensitive to water. Both these products produce adequate alkaline reserves in paper. Since methanol is used as the solvent, the deacidification should be conducted in a well-ventilated hood. 

In consideration of the damage of paper by liquids (solvents) as well as the limitation and effectiveness of transfer chemicals into the fibers, deacidification by gas has been devised. Although there are a great many volatile organic compounds which appear to be sufficient alkaline for vapor-phase deacidification, only a very few appear to be practical. Kathpalia (35), at the Nehru Library in New Delhi, exposed books to high concentrations of amnonia vapor for deacidification. However, it was found that amnonia is a too weak base to completely neutralize strong acid in paper, and amnonia volatilized from treated books in a few days. It has not been considered as a permanent deacidification method. 

Zinc oxide deposited in paper provides an "alkaline reserve (which is more nearly neutral in pH than the more commonly used calcium and magnesium reserves) by reacting with any strong or weak acids introduced into the paper subsequent to the deacidification process ... 

It has been reported that the Vapor Phase Deacidification (VPD) process is versatile and lends itself to a wide, range of techniques which may be adapted to suit the diverse needs of practical document repair for example, the active material CHC may be absorbed on sheets of absorbent paper which can then be used as interleaving in books. By this method, a few sheets of VPD paper, e.g. one sheet to every 50-100 pages of the book, may be evenly spaced throughout the book which is then closed and replaced on its shelf for a week or two. The interleaving process takes only a few minutes and the book should be evenly and completely deacidified with no appreciable change in its appearance. 

A cheaper method well suited to boxed papers and files is to use the CHC in powder form enclosed in small paper envelopes. These packets are simply placed in the boxes with the loose papers and put aside until needed again for reference. The vapor from the CHC should permeate the whole box in a few weeks time and give uniform and satisfactory deacidification. 

The permanence of the deacidification has been tested by heating the deacidified paper samples to 150°C (300F) without increasing the acidity. The vapor from CHC has a very disagreeable odor, that would create an unpleasant atmosphere not only for those handling the material, but also in the stacks of books treated with CHC. CHC is reported to cause nausea and skin and eye irritation (46-54). More importantly, chronic and acute toxic effects have been observed in experimental animals exposed to varying concentration of CHC vapor, sometimes resulting in death (50,54). 

An ideal mass deacidfication process should preserve book papers in a usable condition. For best results, any mass deacidification developed must meet the following criteria ... 

Although many mass deacidifications have been developed, it can be stated that none of the technologies offered meets all the criteria. Nevertheless, the DEZ process, Wei T o process, Kopper Process and VPD have demonstrated independently their potential for arresting paper deterioration from acid. To what extent these processes meet the criteria to be used for a practical mass deacidification process is the question that has to be answered. Accordingly, a comparison of the characteristic features of these processes is tabulated in Table I. The evaluation is based on their neutralization chemistry and effectiveness. The engineering design, safety and costs of these processes are not considered in this evaluation. 

DEZ Process. DEZ process has been developed and refined by chemists at the Library of Congress since 1974. It is a very impressive method of deacidifying book papers effectively and uniformly. There is no doubt that the deacidification chemistry is workable. As shown in Table I, the DEZ process is the process that met most of the "ideal" criteria. In essence, the DEZ process uniformly and consistently neutralizes all excess acid in the paper, leaves a uniformly distributed alkaline reserve in all regions of the book page and the paper fiber. 

The end-product of deacidification is the conversion of sulfuric acid in paper to zinc sulfate. Just like aluminum sulfate, zinc sulfate is prone to dissociate into acid in the presence of water or... 

Koppers "Book Keeping" Process. In view of the limitation of the Wei T o process, chemists at the Koppers Company developed a "Book Keeper" process by dispersing submicron particles of basic metal oxides, hydroxides or salts of calcium, magnesium, or zinc, in a suitable gas such as Freon or liquid medium, so that the active chemicals can be transferred and deposited electrostatically on the surface of paper. It also does not require pre-drying of books as is required for both the DEZ and Wei T o processes. The testing results appear satisfactory as shown in Table I. The major concern with this process is the distribution of the alkaline reserve on the paper. It appears the process deposits alkaline chemicals on the surface of paper and achieves surface deacidification. However, acid formed in the core of the paper is not neutralized. Koppers intends to prove the degrees of chemical penetration and neutralization of acid in the center layers by examination of the cross-section of paper by SEM. 

No reports have been released yet. The effects of the chemical process on paper, covers and inks have not been published. The Koppers process appears to be a unique one with great potential for mass deacidification with success. More testings are required. As with the Wei T o process, the effect of Freon on the ozone layer of the stratosphere is a concern. 

Accordingly, a complete book preservation program should consider (a) complete deacidification (b) improving fold endurance, tear and tensile strength of paper and (c) inhibiting oxidation. 

Based on the information available today on the DEZ process, Wei T o process, Koppers process, and VPD process, it is very difficult to judge which process is the best suited to a mass deacidification process. In addition to the limitations of each process which has been discussed, data are lacking to support long-term effects on treated papers. In order to select a viable mass deacidification process, the following parameters have to be considered ... 

All these important parameters must be established for treated papers so that a meaningful evaluation can be made. Before making any decision on selecting an effective mass deacidification process. 

In addition to the deacidification chemistry, the final decision should also be based on the evaluation of the engineering design, safety of operation and cost factors which have not been considered in this paper. 

G.B. Kelly, Nonagueous Deacidification Treatment en Masse for the Small Workshop. Paper presented at the International Conference on the Conservation of Library and Archive Materials and the Graphic Arts, Cambridge, 1980. 

R. D. Smith, The History and use of magnesium alkoxides in the nonaqueous deacidification of books, documents and works of art on paper. Paper presented at the 1983 Annual Meeting of Internationale Arbeitsgemeinschaft der Archiv-, Bibliothek- und Graphikrestauratoren (LADA), The Hague, Netherlands,... 

J.M. Banks, Mass deacidification at the National Library of Canada. Paper presented at the annual meeting of the Society of American Archivists, Washington, D.C., September 1, 1984. 

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