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4 Paper The word paper comes from papyrus, a sheet made by pressing together very thin strips of the Egyptian reed Cypenls papynls McGovern, 1978~. However, papyrus sheets are not considered paper because the individual vegetable fibers are not separated and then reformed. Paper, by its traditional definition, must be made from natural fiber that has been macerated until each individual filament is a separate unit, the fibers are dispersed in water, and by use of a sieve-like screen the water is drained from the fiber, leaving a sheet of matted fiber on the surface of the screen. When dried, this thin layer of intertwined fiber is paper ~Hunter, 1978~. Modern paper manufacturing equipment employs this same principle in forming the paper web. RAW MATERIALS AND STRUCTURE Cellulosic plant-derived fibers are the raw materials that make up the major part of all papers. Natural plant fibers consist of crystalline filamentous cellulose that is the structure of the skeleton of the fiber. Chemically, cellulose is a linear polymer of beta-D-glucopyranose units linked by 1,4 glycosidic bonds. Isolated samples are found to have molecular weight varying from perhaps 50,000 to more than 1 million for a degree of polymerization of upwards of 7,000 and a length exceeding 0.003 cm. Cellulose has a monoclinic crystal structure characterized by a repeat distance of 1.03 rim t two anhydroglucose units) in the chain, with the repeat units assuming a chair configuration Mark, 1983~. X-ray evidence indi- cates that purified wood and cotton cellulose is about 70 percent crystalline. Lateral hydrogen bonds stabilize the crystal against relative displacement of the chains in response to imposed physical forces. Cellulose is a white substance that is hydroscopic in nature, insoluble in most solvents, and resistant to the action of most chemicals except strong acids. It is a stable organic polymer, and under suitable storage conditions it can be preserved for centuries or millenia without severe deterioration. Natural cellulosic fibers are structurally quite similar, and 33

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34 PRESERVATION OF HISTORICAL RECORDS the fibers of cereal straws, bagasse, kenaf, bamboo, esparto, hemp, jute, flax, cotton, bark, and wood are used to manufacture paper. Wood pulp has proved to be the most important source of papermaking fiber {Emerson, 1980a, 1980b). Bleached chemical wood pulp and cotton fibers can be used to produce high- quality, stable papers. The wall structure of cotton fibers is similar to that of wood fibers; it is relatively thin and grows free of lignin. The molecular weight of cotton cellulose at a degree of polymerization of 8,000 is slightly higher than that in wood, and the crystallites are slightly longer. The longer virgin fibers used in textiles are too valuable to be economical for paper {Rollins, 1965J. However, the cotton ginning operation leaves a fuzz of short fibers on the cotton seed, and these shorter hair fibers, or [inters, together with rags and textile clippings, are the sources of cotton fiber for special papers. Kraft or sulfate pulp is the major wood pulp produced, and it is used for many grades of paper. If white paper or high-brightness pulp is to be produced, lignin and the hemicelluloses must be removed from the pulp fiber by bleaching. Multistage bleaching with agents such as chlorine, chlorine dioxide, caustic extraction, and peroxides is used to produce high-brightness pulp. Chemical wood pulps are clas- sified according to the pulping process used e.g., soda pulp, sulfite pulp, and kraft or sulfate pulp. These three chemical pulps in the fully bleached form are suitable for producing archival papers. The remaining classes of commercial pulps e.g., groundwood, semichemi- cal, and thermomechanical are not suitable for use in archival papers because of their lignin content. Unlike the highly stable crystalline cellulose, lignin is an amorphous, complex, polydisperse polymer network of phenylpropane units with a number of reactive functional groups that changes to a more highly colored form as it ages. For this reason, papers made with lignin-containing fibers tend to discolor with age {Sjostrom, 1981~. Wood fibers are typically from 1.0 to 5.0 mm in length and from 25 to 50 ,um in width and about 5.0 ,um thick. Because of their unique structure, wood fibers exhibit a higher strength-to-weight ratio than any other structural material, with a modulus of elasticity or Young's modulus of 3 x 105 kg/cm2 as compared with 2 x 106 kg/cm2 for steel. The number of fibers per gram will depend on their weight per unit length. Individual fiber weights are in the range of about 1 x 10-6 to 3 x 10-6 g/cm {Corte, 1982J. Browning t1970) has calculated that there are from 1 to 10 million fibers in 1 g and that about 1,000 fibers placed side by side in one layer will span 1 in., showing an average fiber width direction span of 25.4 ,um in the formed web. In forming the paper web, fibers of various dimensions are arranged in an interlocking network to form a sheet whose structure is determined by the spatial distribution and orientation of the various fiber fractions. Fibers in paper lie essentially in the plane of the sheet, giving paper a layered or laminar structure but not discrete layers. This results from the thickening and filtration that take place as the water is removed. In the drying stage of the web, removal of the water permits the establishment of hydrogen bonds between the fibers. Hydrogen bonds are now generally accepted as the cause of mechanical coherence of paper {Corte, 1980~. Nissan { 1983) has pointed out that paper may be treated as a continuum of hydrogen bonds, with the two parameters that deter- mine the modulus of elasticity being the stretch force constants of the hydrogen

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PAPER 35 bonds and the density of such bonds per unit area. He also observes that the hydrogen-bond theory explains the mechanical behavior of paper in terms of inde- pendently derived molecular and thermodynamic parameters. If variance is assumed around the mean value of the hydrogen bond, the rupture energy of paper can be related to the number of hydrogen bonds Nissan, 1983~. Centuries of man's experience with paper have shown that the hydrogen bonds established at the time of manufacture remain intact throughout the life of the paper product, assuming normal storage and use conditions. The strength, integrity, and concentration of the hydrogen bonds in the paper structure help preserve the strength of paper under adverse storage conditions, such as oxidizing atmospheres that degrade the cellulose polymer. On the other hand, if water is reintroduced into the interfiber bond area, it may be absorbed by the hydroxyl groups of cellulose that are associated with the hydrogen bonds of the paper struc- ture. In this way, water can effect reversal of the interfiber bonds and greatly weaken the paper. Although hydrogen bonds are re-established upon removal of the water through drying, they may be displaced, causing cockling of the paper and possible loss of strength. Using this reversible action of water, used paper can be repuiped with water and wetting agents and recycled to form paper products using reclaimed pulp. The properties of these pulps are generally lower in strength and brightness than comparable virgin pulp. Contamination by plastics is also a major problem. Reclaimed fibers are not recommended for archival papers. Many types of nonfibrous raw materials are added to improve the physical, optical, and electrical properties of the resulting paper Browning, 1970; Clark, 1978J. Polymeric binder materials are used to improve the cohesion of the individ- ual fibers and increase the strength and stiffness of the paper. Bonding agents include such materials as starch, modified starches, gelatin, polyvinyl alcohol, methylcellulose, and latex or water emulsion materials such as polystyrene-buta- diene, polyacrylates, and polyacrylamides. Inert inorganic materials known as pigments or fillers are added to fill voids between the fibers and to smooth the surface for printing tHagemeyer, 1984) . Fillers also improve the opacity and bright- ness of the sheet, depending on the particle size, refractive index, and brightness of these materials. Commonly used fillers include clays, talc, calcium carbonate, titanium dioxide, aluminum oxides, and silicates. Pigments are used in varying amounts, depending on the grade of paper, and may comprise 2 to 40 weight percent of the final sheet. Other additives include sizing agents that are used to reduce the penetration of liquids such as offset printing solutions and fluid printing inks. Rosin, starches, and synthetic resins are examples of sizing materials. The sizing agents may be added as part of the paper raw material to produce internal sizing, or the dry sheet may be passed through a size-press coaler that applies a surface size to the sheet. Rosin is the most widely used sizing agent. The rosin is added to the paper stock with one to three times as much aluminum sulfate, which precipitates the rosin on the fibers as flocculated particles; after addition of the alum, the pH should be 4.5 to 5.5. Sodium aluminate may also be used to precipitate the rosin size, thus attaining slightly higher pH papers. Much attention has been focused on the influence of acid conditions encountered during papermaking on the rate of aging of paper. As a result, the production of paper under neutral to alkaline conditions has gained in importance.

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36 .~. PRESER VATION OF HIS TOPICAL RECORDS Photomicrographs of edge and surface of paper showing fiber structure. The paperis a Nekoosa neutra]-pH cotton bond, sub. 20 (76 g/m2J, that meets T A P P ~ , A S T M , a n ~ A N S r e q u i r e m e n t s f 0 r p e r m a n e n c e .

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PAPER 37 Internal sizing of papers under alkaline conditions {pH 7.0-9.0) is achieved with synthetic sizes such as alkyl ketene dimer and alkenyl succinic anhydride. These sizing agents are combined with calcium carbonate filler to provide a useful pH control by a buffering action during aging of the paper. Recent decreases in the cost of calcium carbonate filler and increases in the cost of virgin pulp have created somewhat more favorable economics for alkaline pH paper, resulting in increased commercial interest and production of this type of paper. PHYSICAL PROPERTES A sheet of paper has been defined as a foil with a fibrous fine structure. It is the structure that determines the physical properties of the paper, and any change in structure affects these properties. The properties required for various types of paper, such as bond, writing, printing, book, envelope, and tablet, are developed by the paper manufacturer through fiber selection and refining, type and amount of additives, manufacturing process parameters, and conversion processes includ . , . ng surface coatings. The behavior of the paper structure can be shown by typical stress-strain curves for tension, compression, or shear {Setterholm and Gunderson, 1983~. In the tensile test, when a piece of paper is subjected to a tensile load it stretches in exact proportion to the applied load, and when the load is released it returns to its original length only if the load does not exceed the elastic limit. If the applied load exceeds the elastic limit of the sample and is released, the piece of paper will contract but not to its original length. The permanent length increase is due to inelastic response of some of the elements or of the fibers that are stretched or straightened in the direction of the load. Under constant load above its elastic limit, paper exhibits viscoelastic creep, and at some maximum value of stress the paper undergoes tensile failure. Typically, elastic response will continue for about one-fourth of the failing stress. In a review of paper behavior, Perkins {1983) presents data to show that in a controlled environment paper will exhibit elastic behavior under low loads of short duration, viscoelastic behavior under low loads of long duration, and inelastic behavior as the level of stress increases. He points out that microfailure could be the result of a variety of processes, including tensile fracture of fibers, failure of fiber-to-fiber bonds, and development of slip planes within the fiber cell walls. The inelastic response of paper is similar to other materials such as reinforced fiber composites. In any event, tensile strength is the force parallel to the plane of the sheet that is required to produce failure in a specimen of specified width and length under specified conditions of loading {Technical Association of the Pulp and Paper Industry iTAPPI] T404 and T494, 1984). Stretch is the extension or strain resulting from the application of tensile load under specified conditions {TAPPI T404 and T494~. The initial slope of the load- elongation curve defines the modulus of elasticity or Young's modulus in the machine or cross-machine direction. Stretch is greatest in the cross-machine direction. Tearing strength is the average force required to tear a single sheet of paper under standardized conditions {TAPPI T414~. Fold endurance is the number of folds a paper can withstand before failure {TAPPI T423 or T511). Brightness is the

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38 PRESERVATION OF HISTORICAL RECORDS reflectivity of paper or pulp for light at 457 rim {TAPPI T452~. Color is measured by reflectivity according to TAPPI T442 and T524. Opacity relates to the ratio of the diffuse reflectance of the sheet when backed by a black body to that when backed by a white body {TAPPI T425~. It is well understood that temperature has an effect on paper properties and that moisture content has an even larger effect. Pulp and paper are hydroscopic and can absorb water from or lose it to the surrounding atmosphere. As a result, paper properties will change with changes in relative humidity; therefore, the control of relative humidity in the environment for long-term storage of paper records is very important. The influences of water content on the rate of degradation of cellulose have been reported {Graminski et al., 1978) and show that the effect of tempera- ture was less than that of moisture. A molecular layer of water on cellulose occurs at about 5 percent moisture content, and the mechanical strength properties decrease rapidly when the absorbed water exceeds 5 to 7 percent because of the competition between the water molecules and the hydroxyls of cellulose for the hydrogen bonds with other hydroxyls. In addition, Kadoya and Usuda {1984J found that, at 80 percent relative humidity, the fracture mechanism under load changed from bond breaking to fibers sliding out of the network. It is important to carefully control both temperature and relative humidity in pulp and paper test laboratories and to carefully condition test samples before testing See TAPPI Standard T402-70) to obtain reproducible results. PERNIANENCE FACTORS Aging studies, by a number of investigators, on papers that have retained their properties over very long periods of time, such as books that have survived for centuries, show clearly the importance of composition in the keeping properties of paper. Hudson's {1976) studies identify the quality of the fiber and the level of acidity as key factors in paper permanence. He shows that there is a good correla- tion between cold-water-extraction pH and resistance to heat-aging of paper. Through raw material selection and pH control it is possible to make paper that will store for centuries information of importance to civilizations, and this paper permanence can be increased through the use of controlled storage conditions of temperature and humidity consistent with requirements for use. The potential value of cold storage for books and papers that are not in active use was shown by the work of Hudson jl976) and Hudson and Edwards {1966) on books kept in Antarctica from 1912 until 1959 compared Faith books from the same edition kept in London. Those in the Antarctic were in essentially new condition, while those stored in London showed extensive deterioration. Nakagawa and Shafizadeh ~ 1984) showed that pure cellulose has a high degree of thermal stability up to 300C in an inert nitrogen atmosphere. They investi- gated the rate of change in the molecular weight of cellulose versus time of aging in air at 150C and 190C and found that the rate of change decreases with time of aging. This result agrees with earlier findings that the rate of aging in paper under accelerated aging conditions decreases with time. This indicates that the initial rate of aging for paper under controlled storage conditions, as determined by the rate of change in physical properties such as fold endurance, will decline as the sample ages. Browning ~ 1970) reviewed the role of raw material selection and the

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PAPER 39 value of paper is a major factor in developing and controlling paper permanence and that low-pH papers age more rapidly than neutral to alkaline papers. They give examples of ancient papers that have kept for centuries, many of which remain in good condition today. Test results on these papers suggest that the permanence exhibited is due to an alkaline to neutral pH value or an alkaline filler or both. The

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PRESERVATION OF HISTORICAL RECORDS r o ~ ~ Jay ~ ~ ~ ~ ~:~: ~ it: day., - ~ Y ._ ~ ... Effects of slow-working acidin booLpaper. Peter Waters, conservation officer at the Library of Congress, demonstrates that a heftypuffmakes confetti of dleteriorate~pages.

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PAPER 41 benefit of an alkaline reserve is demonstrated by the keeping qualities of paper contained in a book published in 1801. The paper was made by combining straw pulp and groundwood pulp with chalk as a whitening agent. The paper is in good condition in the personal library of I. d'A. Clark { 1978~. Barrow's { 1960) results on old books showed that one book, published in Venice in the 17th century, that had unusual keeping qualities contained an unusually high level of calcium carbonate filler. This suggests that permanent papers can be produced using refined lignin- free wood pulp that has an alkaline filler. Information based on the composition of such well-preserved centuries-old paper samples has influenced favorably the development of standards and specifications for the production of archival-quality papers See section on Standards and Specifications later in this chapter). Kelly ~ 1972) has shown that for a given type of paper it is possible to calculate the rate of acid development caused by effects from such conditions as rosin-alum size, contact with acid atmospheres tSO2, NOX), and oxidation; also shown is the offsetting effect of an alkaline filler in the sheet. His calculations indicate that the acid generated by the paper-based reactions is neutralized by the excess alkali contained in the sheet. He reviews the possible mechanism for acid generation, including the role of trace metals as oxidation catalysts. As a result, it is proposed that archival paper be made with an alkaline reserve and be free of oxidation catalysts. Both Williams {1979) and Browning t1969) find that the properties required for archival-quality papers are well established. Papers meeting these requirements can be produced using commercially available raw materials, including fiber and filler, and processes that yield neutral alkaline pH in the final sheet. Archival paper records printed on such a paper base will keep for centuries under suitable storage conditions. PRESERVATION The problems of paper preservation associated with the low permanence of acid-sized papers have led to extensive investigations of laboratory- and produc- tion-scale processes for increasing permanence of existing paper records such as maps, charts, documents, and books. Smith and Wilson I 1970) reviewed a number of deacidification procedures, with particular emphasis on a nonaqueous process developed by Smith. This process, involving the treatment of the paper with an organic solvent solution of an alkali or alkaline-earth alkoxide such as magnesium methoxide, has been developed to commercial-scale practice by Smith; the com- mercial-scale process is described in U.S. Patents 3,676,055 and 3,676,182. Williams and Kelly have reduced a method of deacidifying paper to practice {U.S. Patent 3,969,549, 1976), and a commercial-scale facility is currently being planned by the Library of Congress. The method involves exposing the paper to the vapors of diethyl zinc followed by in situ hydrolysis of the zinc compound to a mildly basic material. Barrow and Sproull jl959) proposed deacidification of papers by soaking them in a solution of calcium hydroxide followed by a further soak in a solution of either calcium or magnesium carbonate, which leaves cal- cium carbonate in the paper. Although this method has been widely used by conservators in preserving individual documents, maps, and prints, the wet paper is very fragile and must be handled with extreme care until dry. This process is not practical for large-scale conservation because of the time required and the need for highly trained personnel.

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42 PRESER VATION OF HIS TOPICAL RECORDS The use of magnesium bicarbonate solutions for paper deacidification has been investigated by Wilson and co-workers {1981) at the National Archives. A recent dry process for deacidification, reduced to practice by Kundiot {as described in U.S. Patent 4,522,843), uses an airborne technique to deposit fine particles of MgCO3 on the paper surface. The effectiveness of the process is not known. This development is in accordance with the work of other investigators reported here regarding the effectiveness of an alkaline reserve, which may be added at any time, in extending the useful life of paper. The results from a number of laboratories over many years show clearly that deacidification procedures are effective in reducing the rate of aging of paper that was not produced according to archival standards. The type of deacidification procedure selected would depend on the type of paper or population requiring the treatment. It should be noted that deacidification does not add physical strength to papers that are treated. All of the currently available deacidification processes may damage certain documents through heat, pH changes, or solvent effects on some inks. This makes it necessary to examine individual documents to exclude those subject to damage by the process used. Because individual document screening would be very costly, mass deacidification is not recommended for the unbound Archives collection. A review of the patent literature in the United States and Great Britain by Baer and Hanson { 1983J shows a high level of activity in paper deacidification methods and materials, with about 20 patents issued. In addition to these chemical preservation processes, plastic materials for paper preservation and restoration have been extensively investigated and used. Wilson and Parks { 1983) reviewed and described a number of reports of investiga- tions and actual use of lamination and encapsulation. Their review includes dis- cussion of the importance of mechanical protection with better enclosures and alkaline folders. When paper is encapsulated or laminated, even very old and very fragile paper can be safely handled, thereby prolonging its useful life. The develop- ment and use of a number of preservation methods and materials was reviewed by Roberson {1981~. STANDARDS AND SPECIFICATIONS Kelly and Weberg { 1981 ) reviewed paper specifications developed by a number of organizations for pe~'anent or archival papers, including the Library of Con- gress, the American National Standards Institute {ANSI), the American Society for Testing and Materials {ASTM), the National Bureau of Standards {NBSJ, the Soci- ety of American Archivists, and Barrow Laboratories. The specifications listed for paper permanence include a pH of 7.5 to 10.3, at least a 2 percent calcium carbo- nate reserve in the paper, and the absence of lignin or groundwood pulp. It is estimated that papers meeting the specification should have a probable life of 500 to 1,000 years under good storage conditions. Work on the development of specifi- cations at the National Bureau of Standards, including literature on the stability of paper, was reviewed by Wilson (1974~. A general review of the principles involved in alkaline sizing, which is specified for permanent paper, was presented by Tosh {1981~. Sizing agents that operate without alum, such as alkyl ketene dimers or anhydrides, are recommended.

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PAPER 43 e:: _~ . ~ `' Hi, :~ ":A:~ :: ~ ,,:i A i:. I.,: "'"I : :'~ , , i .,, '.:i ~. :, < ~ it, hi 'A < ~-myth ~ "A 'I ~ ''.~'` ~ Hi,, - : ,, i,, i. Hi.. : Document encapsulation. Paper that is too fragile forhnndling can be protected between sheets of transparentpJasticfi~m.

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44 PRESER VATION OF HIS TOPICAL RECORDS Specifications for papers for permanent records have been published by ANSI and ASTM. Test methods applied to paper have been published by the Technical Association of the Pulp and Paper Industry {TAPPI). Each TAPPI standard for permanent paper designates three levels of permanence: Type I, Maximum Per- manence, pH 7.5-9.5; Type II, High Permanence, pH 6.5-8.5; and Type III, Medium Permanence, pH 5.5 minimum. In addition, a 2 percent calcium or magnesium carbonate filler level is specified for Type I papers. The ANSI and ASTM standards are designated D3290-76, Bond and Ledger Paper for Permanent Records; D3208-76, Manifold Papers for Permanent Records; D3301-74, File Fold- ers for Storage of Permanent Records; D3458-75, Copies From Office Copying Machines for Permanent Records; and Z39.48-1984, Permanence of Paper for Printed Library Materials. For the creation of paper records meeting archival quality standards, perma- nent or archival paper should be used in combination with permanent or archival- quality image-forming materials. Printing inks for printing presses and toners for copying machines are a combination of pigments or colorants with a resin to bind the pigment to the paper surface. A wide selection of both types of raw materials is available to the ink and toner manufacturer, including materials of proved long- term stability such as carbon black and colored stable inorganic pigments and stable types of resin such as polyesters, polyamides, acrylics, and phenolics. Not all inks and toners are designed for long-term stability; therefore, archival require- ments should be applied in the selection of these materials for the creation of archival-quality records. In addition, both the printing process and the copying process should be operated under conditions that are optimum for promoting a strong bond between the ink or toner and the paper surface. If these materials are used in well-adjusted processes in combination with archival-quality paper {ASTM D3458-75), the resulting paper record will keep under good storage condi- tions for many centuries. A useful reference for guidance in selection of archival- quality inks and toners and the xerographic process is the Printing Ink Manual {1979~; see also Diamond il984) and Parks and Wilson {1974~. ADVANTAGES, DISADVANTAGES, AND CONCLUSIONS Advantages The advantages of paper as an archival material are these: 1. The permanence of paper generally demonstrated through many centuries of storage in collections throughout the world is an advantage for archival use. 2. The ease of producing copies of paper documents as a result of the worldwide proliferation of copiers and duplicators in offices, libraries, airports, hotels, etc., is an advantage for paper-based records. The copying process has no discernable detrimental effect on the original. 3. Printers or "intelligent" copiers that produce paper copies directly from computer-based records are an advantage in computer-based record systems. These copiers can print a variety of information using computer-generated for- mats at any location using satellite or telephone-line transmission. 4. The ready availability of neutral pH paper at regular commercial prices for

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PAPER 45 use in generating archival-quality papers is an advantage today that did not exist a few years ago. Disadvantages Paper's disadvantages are as follows: 1. Papers that are acid-sized show degradation during storage, and deacidifica- tion may be needed to extend their useful storage life. 2. Many of the early copier and duplicator processes developed fragile or unsta- ble copies that do not have longevity. In some cases the images were composed of dyes that fade with time. 3. Paper-based records are bulky and involve manual operations. Conclusions The following conclusions regarding paper are drawn: 1. Experience with use and storage of paper records over many years has demon- strated the centuries-long permanence of paper produced with near-neutral pH made from bleached pulps and with an alkaline reserve. 2. Images formed on permanent paper with inks from printing presses or toners from photocopying machines that use permanent-type materials such as carbon black pigment and inert resin binders {e.g., polyester, silicone, polystyrene, and epoxy) will remain legible for hundreds or thousands of years if protected by suitable storage conditions. 3. The permanence of all papers can be extended through the use of proper environmental conditions such as low temperatures, humidity control, and dark storage. 4. Paper produced with an internal acidity below 5.5 pH and without an alka- line reserve will have a lower degree of permanence, but increased permanence can be achieved with treatment by laboratory or commercial deacidification methods and the introduction of an alkaline reserve at any time during the paper's useful life. Remedial actions include {aJ treatment by an alkalization process, such as deposition of magnesium bicarbonate, when the original documents must be preserved and {b) copying onto permanent paper with permanent toners to provide long-term stability when the intrinsic value of a document is not important. This procedure is particularly recommended when only part of a set or random sheets of documents are to be preserved. 5. Papers that are damaged physically or that have become weak from aging effects may be safely protected through encapsulation using acid-free alkaline- reserve permanent papers or inert materials such as Mylar polyester film. 6. Under suitable storage conditions, the rate of aging decreases with time. Paper that is shown by tests to be aging slowly will change to a lower aging rate if stored under proper environmental conditions. 7. Inactive paper records may be safely stored at reduced temperature, includ- ing below-freezing cold storage conditions, to extend their useful life.

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46 PRESERVATION OF HISTORICAL RECORDS REFERENCES Baer, N. S., and K. Hanson. 1983. Survey of Patent Literature Pertaining to Deacidification of Archives and Library Materials. New York: New York University Conservation Center of the Institute of Fine Arts. Barrow, W. J.1960. The Manufacture and Testing of Durable Book Papers, R. W. Church, ed. Publica- tion 13. Richmond, Virginia: Virginia State Library. Barrow, W. J., and R. C. Sproull. 1959. Permanence in book papers. Science, 129:1075-1084. Browning, B. L. 1969. Analysis of Paper. New York: Marcel Dekker. Browning, B. L. 1970. The nature of paper. Libr. Q., 40(1):18-38. Browning, B. L., and W. A. Wink. 1968. Studies on the permanence and durability of paper. Tech. Assoc. Pulp Pap. Ind. J., 5114~:156-163. Cardwell, R. D., and P. Luner. 1978. Thermogravimetric analysis of pulp; kinetic treatment of dynamic pyrolysis of papermaking pulps. Tech. Assoc. Pulp Pap. Ind. J., 61(8):81-84. Clark, J. d'A.1978. Filling and bonding materials. Chapter 311pp. 664-678) in Pulp Technology and Treatment for Paper. San Francisco: Miller Freeman Publications. Corte, H. 1980. Cellulose water interactions. Chapter 1 (pp. 1-89) in Handbook of Paper Science, Vol. 1, H. F. Rance, ed. New York: Elsevier. Corte, H.1982. The structure of paper. Chapter 9 (pp.175-282) in Handbook of Paper Science, Vol.2, H. F. Rance, ed. New York: Elsevier. Diamond, A. S. 1984. Toner and Developer Industry Update. Ventura, California: Diamond Re- search Corp. Duswalt, A. A. 1977. Thermal analysis study of paper permanence. Chapter 23 in Preservation of Paper and Textiles of Historic and Artistic Value, J. C. Williams, ed. Am. Chem. Soc. Adv. Chem. Ser. 164. Emerton, H. W. 1980a. The fibrous raw materials of paper. Chapter 2 IPP. 91-138) in Handbook of Paper Science, Vol. 1, H. F. Rance, ed. New York: Elsevier. Emerton, H. W. 1980b. The preparation of pulp fibers for paper making. Chapter 3 (p. 139) in Handbook of Paper Science, Vol. 1, H. F. Rance, ed. New York: Elsevier. Graminski, E. L., E. J. Parks, and E. E. Toth. 1978. The effects of temperature and moisture on the accelerated aging of paper. Pp. 341-355 in Durability of Macromolecular Materials, R. K. Eby, ed. Am. Chem. Soc. Symp. Ser. 95. Hagemeyer, R. W., ed. 1984. Pigments for Paper. Tech. Assoc. Pulp Pap. Ind. Papers. Hudson, F. L. 1976. The permanence of paper. Pp. 714-723 in The Fundamental Properties of Paper Related to Its Uses, F. Bolam, ed. Trans. Fundam. Res. Symp., Cambridge, 1973. London: Technical Section of the British Paper and Board Makers Association. Hudson, F. L., and C. J. Edwards.1966. Some direct observations on the aging of paper. Pap. Technol., 7~1):27-31. Hunter, D. 1978. Papermaking-The History and Technique of an Ancient Craft. New York: Dover Publications, p. 5. Kadoya, T., andM. Usuda. 1984. The penetration ofnon-aqueousliquids. Chapter 19 {pp. 123-141} in Handbook of Physical and Mechanical Testing of Paper and Paperboard, Vol. 2, R. E. Mark, ed. New York: Marcel Dekker. Kelly, G. B. 1972. Practical aspects of deacidification. Bull. Am. Inst. Conserv., 13(1):16-28. Kelly, G. B., andN. Weberg.1981. Specifications and test for alkaline papers. Pp.71-76inTechnical Association of the Pulp and Paper Industry Papermakers Conference Proceedings {April). Atlanta: TAPPI Press. Luner, P. 1969. Paper permanence. Tech. Assoc. Pulp Pap. Ind. J., 52(5~:769-805. McGovem, J. N. 1978. Pulp Paper, 52~9~:112. Mark, R. E., ed. 1983. Mechanical properties of fibers. Chapter 10 {pp. 409-495) in Handbook of Physical and Mechanical Testing of Paper and Paperboard, Vol. 1. New York: Marcel Dekker. Mendenhall, G. K., G. B. Kelly, and J. C. Williams. 1981. The application of several empirical equations to describe the change of properties of paper on accelerated aging. Pp. 177-188 in Preservation of Paper and Textiles of Historic and Artistic Interest, Volume II, J. C. Williams, ed. Am. Chem. Soc. Adv. Chem. Ser. 193. Nakagawa, S., and F. Shafizadeh. 1984. Thermal properties. Chapter 23 {pp. 241-279) in Handbook

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PAPER 47 of Physical and Mechanical Testing of Paper and Paperboard, Vol.2., R. E. Mark, ed. New York: Marcel Dekker. Nissan, A. H.1983. Retrospect and prospect of testing. Chapter l lpp. 1-19) in Handbook of physical and Mechanical Testing of Paper and Paperboard, Vol. 1, R. E. Mark, ed. New York: Marcel Dekker. Parks, E. J., and W. K. Wilson. 1974. Evaluation of Archival Stability of Copies From Representative Office Copying Machines. National Bureau of Standards Report No. 74-498(R), April 30. Perkins, R. W.1983. Elastic, viscoelastic, and inelastic behavior. Chapter 2 (pp.23-75) in Handbook of Physical and Mechanical Testing of Paper and Paperboard, Vol.1., R. E. Mark, ed. New York: Marcel Dekker. Printing Ink Manual, 3rd edition. 1979. London: Northwood Books. Ramiah, M. V. 1970. Thermogravimetric and differential thermal analysis of cellulose, hemicellu- lose and lignin. J. Appl. Polym. Sci. 1415~:1323-1337. Roberson, D. D. 1976. The evaluation of paper permanence and durability. Tech. Assoc. Pulp Pap. Ind. J., 59(12):63-69. Roberson, D. D.1981. Permanence/durability and preservation at the Barrow Laboratory. Pp.45-55 in Preservation of Paper and Textiles of Historic and Artistic Interest, Volume II, J. C. Williams, ed. Am. Chem. Soc. Adv. Chem. Ser. 193. Rollins, M. L.1965. The cotton fiber. Pp.44-79 in The American Cotton Handbook, 3rd edition, Vol. 2, D. S. Hamby, ed. New York: Interscience. Sclawy, A. C., and J. C. Williams. 1981. Alkalinity, the key to paper "permanence." Tech. Assoc. Pulp Pap. Ind. J., 64~5~:49-50. Setterholm, V. C., and Gunderson, D. C. 1983. Observations on load deformation and testing. Chapter 4 (pp. 115-143) in Handbook of Physical and Mechanical Testing of Paper and Paper- board, Vol. 1., R. E. Mark, ed. New York: Marcel Dekker. Sjostrom, E. 1981. Wood Chemistry Fundamentals and Applications. New York: Academic Press. Smith, R. D., and W. K. Wilson. 1970. New approaches to preservation of library materials. Libr. Q., 40(1):139-175. Technical Association of the Pulp and Paper Industry. 1984. Combined Test Methods Manual. Atlanta, Georgia: TAPPI Press. Tosh, C. 1981. Durability of paper. Paper {London), 195(9~:26-30. Williams, J. C. 1979. Paper permanence: A step in addition to alkalization. Restorator, j3~:81-90. Wilson, W. K.1974. Development of Specifications for Archival Record Material. National Technical Information Service Report COM-75-10131. Wilson, W. K., and E. J. Parks. 1980. Comparison of accelerated aging of book papers in 1937 with 36 years of natural aging. Restaurator, (4):1-55. Copenhagen: Munksgaard. Wilson, W. K., and E. J. Parks.1983. Historical survey of research at the National Bureau of Standards on materials for archival records. Restaurator, {5):191-241. Copenhagen: Munksgaard. Wilson, W. K., R. A. Golding, R. H. McCloren, and J. L. Gear. 1981. The effect of magnesium bicarbonate solutions on various papers. Pp. 87-107 in Preservation of Paper and Textiles of Historic and Artistic Interest, Volume II, J. C. Williams, ed. Am. Chem. Soc. Adv. Chem. Ser. 193.

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~;~ Film storage facilityin Granite Mountain records vault of the Genealogical Society of Utah. Control of storage conditions is vital to ensure permanence of stored records.