Deacidification methods

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. 

Moreover, recently Book Preservation Associates and Lithco have announced new mass deacidification methods. These processes should be considered if data are available. 

Standard acidification and deacidification methods are aimed solely at changing total acidity levels, with no concern for the impact on pH and even less for the buffer capacity of the wine, with all the unfortunate consequences this may have on flavor and aging potential. 

Ribeiro et al. tested three different lipolytic preparations obtained from Thermomyces lanuginosus (immobilized), Candida antarctica (liquid), and Yarrowia lipolytica (liquid) for the hydrolysis of buriti oil, reaching values around 75 %, 35 %, and 18 % of yield of free fatty acids, respectively, without considerable losses in the total carotenoid content. After hydrolysis, carotenoids were concentrated up to 3,900 ppm by deacidification methods, such as partition using ethanol, as well as winterization, thus removing 70 % of the free fatty acids [80]. 

The buffer established by the DEZ process is more neutral (saturated solution with a pH of 7.3-7.5) than that of magnesium or calcium salts used in other deacidification methods. 

A. Lienardy, A Bibliographical Survey of Mass Deacidification Methods, Restaurator 1991, 12, 75-103. 

In addition to malo-lactic fermentation, another biological method for deacidification of high-acid must is to use malic acid-metabolizing Schizo-saccharomyces yeast for the alcoholic fermentation. Benda and Schmidt (33) have selected strains of these yeasts which produce wines with no off-flavors. In using some of these same strains we have also been able to make wines of sound character (18). 

Princeton University Libraries and at the British Library. The mass deacidification of the Wei T o process has been used in the National Library and Public Archives of Canada (34). Just like any method,... 

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. 

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. 

In a German method, applied at the Kriimmel factory, the crude acid TNT, after it has been washed free from nitrosylsulphuric acid, is washed several times with water at a temperature of 90°C in brick washing vats lined with sheet lead, or in stainless steel tanks. The deacidification is finally followed by neutralization with an NaHC03 solution of concentration about 1%. The product obtained in this stage has a freezing point of 78.8-78.3°C. 

Much of this material should be deacidified, but only the experienced can decide whether aqueous or nonaqueous methods should be used, and only they are likely to have the manual dexterity and knowledge of handling techniques which in many instances are essential if damage is to be avoided. The method of deacidification depends on the nature of the paper and inks and pigments. Sometimes the paper cannot be treated at all because the colors of the image would be changed. 

The detrimental effect of acid in paper has been well documented (1, 2, 3, 4), and numerous treatments have been proposed to alleviate the effect. Schierholz (5), Barrow (6), and others have proposed methods of neutralizing the acids in paper based on aqueous treatments. However, many papers are sensitive to aqueous treatments, either because of the fragility of the paper or the tendency of the inks or colors to run when exposed to water, and for these papers a nonaqueous deacidification treatment is required. 

The problem of mass vapor-phase methods for the deacidification of books or textiles has received a great deal of attention in the last few years. Such treatments are best applied to current books in which the paper is still strong. Rebuilding strength into textiles or books by a vapor-phase treatment is eminently desirable. Both problems are discussed in this volume. When solved, the processes will probably be carried out in special plants by chemists rather than by conservators. 

Ever since the beginning of deacidification, the desirability of methods that do not require taking a book apart has been apparent. Barrow tried to deacidify with ammonia but the effect did not last. In 1963, he was working on a process in which the pages of a bound book... 

Paper may be deacidified to make it more permanent. Since the paper often has become brittle before it is treated, methods are needed for increasing folding endurance that may be applied in conjunction with deacidification. In this study, the effects of sorbitol and Hercules Kymene 557H on the folding endurance of three papers alkalized with magnesium carbonate are explored. A synergistic action of the reagents is apparent. 

T veacidification plus the incorporation of an alkaline reserve greatly extends the life of acid paper. However, the treatment does not restore the pliability and folding endurance that have been lost. There is a need for a method that will regenerate these properties. This should be ultimately a mass method and should preferably be carried out in conjunction with one of the mass deacidification treatments presently being developed. 

The measurement of acidity in paper documents with cold- and hot-water extraction frequently distorts and damages the paper fibers and printing inks. Many paper conservators and museum curators have long desired a reliable and rapid method for the detection of acidity of paper documents in a nondestructive manner so that they can determine the acidity routinely to screen out valuable book documents for deacidification or other necessary preservation treatments. The objective of this chapter is to introduce two spectroscopic techniques, namely, Fourier transform IR spectroscopy (FTIR) and electron spectroscopy for chemical analysis (ESCA), for chemical analysis of paper surfaces. The effectiveness of these techniques in analyzing and determining the presence of acidic functional groups on paper documents is demonstrated. 

To assess the feasibility and to verify if the ED operations of the EDBM2C configuration could be expensive because of the NaOH and energy consumption, the authors recently published a work comparing this method with different methods used for deacidification of clarified passion fmit juice [18]. They compared EDBM with other physicochemical technologies, ion-exchange resins, and electrodialysis with homopolar membranes (Figure 21.25), as well as the conventional chemical method based on the precipitation of calcium citrate obtained by addition of calcium hydroxide or carbonate to the clarified juice. 

Several methods exist for deacidification of fat or oil. The choice depends on the amount of free fatty acidspresent in crude fat or oil. The removal of fatty acids with 15% sodium hydroxide (alkali refining) is the most frequently used method. Technically, this is not very simple since fat hydrolysis has to be avoided and, moreover, the sodium soap (the soap-stock ), which tends to form stable emulsions, has to be washed out by hot water. After vacuum drying, the fat or oil may contain only about 0.05% free fatty acids and 60 to 70 ppm of sodium soaps. When the fat or oil is treated with diluted phosphoric acid, the content of sodium soaps decreases to 20 ppm and part of the trace heavy-metal ions is removed. 

There are many statements in literature about different deacidification systems and agents, its advantages, use and also comparative examinations [10-15]. In the treatment a long-term add protection (exogenous influences) is to be achieved and therefore an additional alkaline buffer is deposited in the paper [17-23]. In the follovdng the most important methods are introduced. 

On the one hand the deacidification systems can be divided into single sheet methods and mass deaddijication methods. On the other hand the methods can differ in the polarity of the solvents used. Polar solvents have a swelling effect on cellulose, or rather paper, and can dissolve some of the colors and inks and therefore mostly nonpolar solvents are used in mass deacidification systems. Single sheet methods with water as a treatment medium are the classical methods. 

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