ritzenthaler 19-43

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Ritzenthaler, Mary Lynn, Nature of Archival Materials, Preserving Archivesand Manuscripts, Chicago: Society of American Archivists, 1993, pp. 19-43

The material nature of the archival record is diverse and potentially limitless,depending upon what is seen as having archival significance and thus is accessioned into arepository. Most institutions have their share of strange and wonderful objects, such aspieces of wedding cake, portraits executed in macaroni, and letters written on two-by-fours(see Figure 3-1).1 Rapid changes in the technology of recording and transmitting

information will have a great impact on the archives of the future. Record materials that aretraditional by today's standards eventually may be largely replaced by electronic media. Inthe meantime, however, archivists must have an understanding of more common materialsand structures. This includes familiarity with (1) the support or base materials traditionallyused for collection items, such as paper, glass, plastic film, and animal skin, and (2) themedium, or manner, in which the information was recorded. Archivists must be able torecognize the material nature of the records in order to make informed decisions regardinghandling, use, storage, and preservation requirements.

Beyond recognizing the various materials that are most likely to be represented in acollection, the archivist also must understand how component materials work together.Most archival records are complex rather than simple assemblages. They may be composedof many materials, and also may have interdependent mechanical properties. A ledger, for

example, consists of paper, inks, boards, adhesives, thread, and covering material. Ideally,these components function compatibly and in unison to preserve and allow access toinformation. If any element breaks down, however, the archivist should be able to evaluatethe problem and select the appropriate preservation option.

Since archival records can be complex physical and chemical objects having veryspecific handling and treatment needs; a primary responsibility of the archivist is tobecome acquainted with the increasingly wide range of record materials, both historicaland contemporary. In order to plan deliberately for their storage and care, it is important toknow which processes, materials, and images are fragile, vulnerable, or ephemeral. Alsoessential is an understanding of how the structural elements of an object-book, scrapbook,film-relate to accessing and preserving its informational content (see Figure 3-2). The archi-vist must be able intellectually to break down a record into its component parts and toconsider its format and content as well as its physical condition, in order to developsystems to manage and preserve the (sometimes fragile) whole.

PaperPaper is the most common material found in archival collections. While the precise historyof its development is somewhat murky, the invention is attributed to the Chinese, andpaper samples have been found dating back to 200 B.C.2 Papermaking was primarily ahand process until the invention of the Fourdrinier papermaking machine, which was putinto operation in 1803.3 Paper may be defined very simply as fibers that have been reducedto pulp, suspended in water, and then matted into sheets. Although a wide range of fibrousmaterial may be used to form paper, it is made primarily from plant fibers, such as cotton,

wood, flax, straw, and mulberry, which are rich in cellulose. Cellulose, the most importantconstituent of paper, is composed of hydrogen, carbon, and oxygen. It is a stable, naturallyoccurring polysaccharide polymer that serves as the structural element for plants, formingthe walls of plant cells. Besides cellulose, plant fibers contain sugars, starches, carbo-hydrates, and lignin (the non-carbohydrate, non-fibrous substance in the cell walls of livingplants that is responsible for their strength and rigidity, but that in paper contributes to itsdegradation).

During the hand papermaking process, suitable fibers are soaked in water, cooked in


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Preservation Sampler #3: Archives, p. 2

caustic soda and ash, and often fermented. The fibers are then macerated or beaten so thatthey flatten out and small hairlike fibers called fibrils develop: The fibrils remain attachedto the fibers and provide a greater surface for bonding during sheet formation. Originally,beating was done by hand, as it still is today in some papermaking processes in variousparts of the world. However, the water-driven stamping mill, invented in the twelfthcentury, speeded up the process and still produced a relatively long fibered pulp throughthe use of wooden beaters (or stampers) in a wooden tub. Once the fibers are macerated toa pulp, they are added to a vat of water to form a dilute slurry. The water swells the fibers,distributes them evenly in the suspension, and promotes hydrogen bonding, which holdsthe dry fibers together. A paper mold is dipped into the vat vertically, lifted out hori-zontally, and shaken vigorously until an even layer of slurry rests on the porous screen ofthe mold (see Figures 3-3, 3-4). The slurry is retained by the surround, or top half of themold, called the deckle (see Figure 3-5). Excess water passes through the screen, whichtraps the fibers, and the remaining mat of fibers is laid (or couched) onto a piece of woolfelt. The paper sheet is formed by mechanical intertwining of the fibers, surface tensionbetween fibers, and chemical bonding of adjacent cellulose molecules (i.e., hydrogenbonding).

Once a stack of sheets has been made and layered between pieces of felt, additionalwater is removed by pressing and air drying (see Figure 3-6). Sizing is added to allow thepaper to accept writing and printing inks. Without sizing, paper behaves like a blotter and

inks applied to it feather and spread. Unsized sheets are known as water leaf. Traditionalsizing agents were animal glue and gelatin, which were applied by immersing dry sheetsinto tubs of hot size. Some contemporary handmade papers are still sized with gelatin,although synthetic sizing agents are also employed.4

Handmade paper generally does not have a dominant grain direction because thefibers are aligned randomly as the papermaker manipulates the mold after lifting it fromthe vat. This means that handmade paper will usually neither tear nor fold more readily inone direction than another. Since paper made by hand is formed individually sheet bysheet, no two pieces are exactly alike, nor is a single sheet of uniform thickness throughout.Unless handmade paper has been cut or trimmed (which is seen as sacrilege by some), ithas a distinctive deckle (or feathered) edge around all four sides, formed as slurry seepsbetween the deckle and frame of the mold. Papermaker's tears are another distinctive

characteristic of some handmade paper. These small roundish impressions in the paper,somewhat thinner than the surrounding area, result if a drop of slurry falls onto the newlyformed sheet, forcing the fibers to disperse slightly.


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Figure 3-1. This roll petition has both artifactual and informational value, and poses a greatstorage and access challenge. (Courtesy ofthe National Archives and Records Administration.)

Figure 3-2. This volume is of a size that almost defies standard handling and housingprocedures; it exemplifies the inability of some binding structures to support and protectlarge, heavy textblocks. (Courtesy ofthe Library of Congress.)

Handmade paper often contains a watermark, a design that can be seen in the

finished sheet through transmitted light. Watermarks were first used in Italy at the end ofthe thirteenth century and were commonly used throughout Europe by the fifteenth cen-tury. This bent wire design or symbol is attached to the grid of the mold. During sheetformation, fewer fibers settle over the design, resulting in greater translucency in thislocalized area. A smaller and subsidiary watermark known as the countermark, introducedin the seventeenth century and placed in the opposite half of the sheet to the mainwatermark, often contained the name or initials of the papermaker as well as the date andplace of manufacture. Watermarks are important bibliographic tools in identifying and


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dating paper.The process of making paper by machine is essentially the same as the simple hand

process outlined above, although the scale is obviously much larger and the steps aremechanized. Also, on the Fourdrinier-style machine, the paper is formed in a continuousroll rather than in individual sheets. The fiber mat is formed on a high-speed screen andcarried through successive steps to drying, calendering (i.e., running the paper betweenrollers to give it a smooth surface), and finishing (see Figure 3-7). If desired, a dandy roll isemployed when the fibers are still wet to impress a design (such as laid and chain lines tosimulate handmade paper) or watermarks into the newly formed paper as it passesbeneath the revolving roll. Machine-made paper has two deckle edges formed by strips ofsoft rubber along each side of the machine to prevent the slurry from running off, althoughit can be manufactured with four simulated deckle edges. Imitation deckle edges also canbe created on dry paper by various methods of tearing or cutting. Machine-made papershave a definite grain direction; the fibers align themselves in the direction of the movingscreen. Paper will fold and tear more readily with. the grain than against it. Also, whenmachine-made paper is dampened or pasted, the fibers swell or expand across their widthto a greater degree than along their length. This characteristic has implications for printers,bookbinders, and paper conservators, who must know the working properties of the paperwhen it is exposed to moisture or wet treatment.

Unfortunately, the quality of paper has steadily declined since the late eighteenth

century. Prior to that time, papermaking was primarily a handprocess using cotton andlinen rags as the source of cellulose. As noted above, the fibers were beaten in a stampingmill, which retained much of their length and resulted in the formation of fibrils that didnot separate completely from the fibers. Also, no additives were used that had adeteriorative effect on the paper. Paper from this period is generally still quite strong andflexible.

As the demand for paper increased, forcing greater mechanization, processes andmaterials were introduced that resulted in much poorer quality paper. By the mid-seventeenth century, alum (potassium aluminum sulphate) was added as an agent toharden the gelatin sizing as well as to control the growth of mold and bacteria in the hotgelatin. The presence of alum, a hydrated double salt that in the presence of moisturebreaks down to-form several products, including sulphuric acid, greatly diminishes the

useful life of paper. The Hollander beater was invented in the Netherlands in about 1680 tomacerate the fibers mechanically using metal blades against a metal bed plate. TheHollander beater, which replaced the water-driven stamper, speeded up the pulpingprocess but also produced a shorter rather than the more desirable longer fibered pulp. Theaction of the metal blades against the metal plate also left small metallic particles in thepulp. Metallic traces in paper can catalyze deteriorative chemical reactions and maycontribute to the formation of foxing. The water used in the papermaking process can beanother source of trace metals. In 1774, chlorine was introduced to bleach colored rags to atone considered acceptable for paper. If not completely removed, residual chlorine-a strongoxidizing agent-reacts in the presence of moisture to produce hypochlorous acid, which isdamaging to cellulose.

In the decade between 1840 and 1850, alum rosin sizing became widely used as a

replacement for gelatin, because it could be added directly to the vat rather than appliedafter sheet formation, making the process faster and more economical. Alum was used inconjunction with rosin (the actual sizing agent) to insure that the rosin was precipitated onthe paper fibers. Alum also aided in the dispersal of plant fibers in the slurry."Papermaker's alum" (aluminum sulphate), developed in the late nineteenth century foreconomic reasons, was even more acidic than the earlier alum compound and thereforecontributed even more to the decline in paper stability.

In the late eighteenth century, increased literacy and recordkeeping surpassed the


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availability of rags for paper, and other sources of plant fibers were sought that would beboth plentiful and cheap. Experiments were made with a wide range of curious andwonderful fibers, from potatoes to wasps' nests; but by the middle of the nineteenthcentury wood pulp was being used extensively to create inexpensive papers.5 Wood is theprimary source of cellulose fiber for paper being produced today. Depending upon species,wood consists of approximately 45 percent cellulose, 6 20-25 percent hemicelluloses,7 16-34percent lignin, and less than 5 percent of other substances. Groundwood pulp, which isproduced by mechanically grinding or macerating wood into separate fibers as its nameimplies, does not produce stable paper. After the bark is removed, logs are ground on arevolving stone. The resulting pulp retains all of the components of wood, except forwater-soluble materials, which wash away during the grinding process. The fibers areshort, and a large amount of lignin (which is unstable, light-sensitive, and breaks downinto acid compounds as it ages) is retained.8

While groundwood paper is always unstable, it is possible to obtain relatively strong,high-quality paper from wood pulp that has been chemically treated to remove as much ofthe lignin and other non-cellulosic material as possible.9 Chemical wood pulp is created bycooking chips of wood in various chemical solutions under pressure at high temperature.The cellulose fibers are left in an aqueous suspension and then bleached and washed toremove lignin and other undesirable materials. The soda process employs caustic soda tocook the wood chips and produces a soft, short-fibered, and relatively weak paper. The

sulphite process uses a solution of calcium bisulphite for cooking the wood and creates astronger, longer-fibered paper than does the soda process. The sulphate or kraft process,which is now the dominant chemical pulping process, employs sodium sulphide as theprimary cooking agent, and produces the strongest of the chemical wood pulps. The chemi-cal wood pulping processes preserve a much longer fiber than does the mechanical woodpulping process, which is a contributing factor to paper strength and durability.

Figure 3-3. This demonstration of Japanese-style sheet forming at the University of IowaCenter for the Baok papermaking facility shows the technique of building up layers of pulpon the su, or flexible papermaking screen. (Courtesy ofthe UI Foundation.)


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Figure 3-4. Having formed the sheet, the vatman lets excess water drain away beforeremoving the deckle from the mold. (Courtesy ofthe author.) -

Figure 3-5. Paper mold with watermarking wires. (Drawing by Pamela Spitzmueller.)


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Figure 3-6. A stock of newly formed sheets of paper layered between felts is placed in onhydraulic press to remove additional water and compress the fibers. (Courtesy ofthe author.)

Figure 3-7. A continuous web of paper is made on a papermaking machine. (Courtesy oftheauthor.)

Paper made today is much more complex than at produced in previous centuries.

Many substances in varying combinations are added to the pulp to achieve desired results,in addition to the sizing agents described above. For example, fillers are added to improvethe color (often whiteness) of the paper, to achieve a smooth sheet that has good printingqualities, and to improve the dimensional and chemical stability of the paper. Fillers maybe natural, such as clay, talc, or ground limestone (i.e., chalk), or they may bemanufactured, such as titanium dioxide or precipitated calcium carbonate. Opticalbrighteners and fluorescent dyes are added to enhance paper brightness. "Wet-strength"additives (various resins) are added to the pulp to achieve a paper that will retain itsstrength when wet. All of these additives, and the various finishing processes, have a directbearing on the chemical and physical properties of the paper, as well as on its appearance,texture, and surface characteristics.

Paper technology and the paper industry are ever-changing, in response to technical

innovations, the availability of natural resources, environmental concerns, economics, andconsumer requirements. Since the 1960s, whole trees have been converted to chips at theharvest site, which has resulted in less waste. Hardwoods are increasingly being used for apulp source as softwood forests become depleted, and the use of recycled fibers from wastepapers and sawmill waste has also increased. In the pulping process, grinding stones arebeing replaced by disk refiners that can digest wood chips and sawdust, thereby achievinga high yield. Thermomechanical pulp (TMP), produced by heating wood chips under pres-sure and passing the softened chips through a disk refiner, achieves a stronger fiber than


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does traditional ground wood pulp, although lignin is retained. Chemithermo mechanicalpulp (CTMP), another recent innovation, also contains lignin but not groundwood. Suchinnovations have a direct impact on the physical and chemical properties of the paperproduced, and must be considered in efforts to achieve standards for permanent paper.Changing methods of pulping, the use of different pulp combinations, the addition ofvarious nonfibrous additives, and the evolution of physical and chemical treatmentscarried out during paper manufacture, combine to make contemporary paper wonderfullydiverse and complex. While papermaking relies greatly on science, art and craft (andperhaps a little magic) still have a place in the process.

Acidity in Paper

The period from 1850 to the present has often been considered "the era of bad paper."The quality of paper progressively declined, primarily as a result of the increased use ofalum rosin sizing and groundwood pulp, both of which introduced a high degree of acidityinto paper. Other sources of acid include residual bleaching chemicals, inks, sulphurdioxide and other acid-forming pollutants, and migration. Acid migration (or transfer)refers to the ability of acid to move from an acidic material to items of less or no acidity.This transfer takes place through direct contact with adjacent acidic materials (for example,secondary materials such as manila file folders as well as poor quality papers such asnewspaper clippings), or through exposure to acidic vapors in the surroundingenvironment (such as a closed box or file drawer). Acidity is one other primary causes of

paper deterioration. Acidity causes paper to lose its strength by hydrolysis of its cellulosemolecules; the polymer chains gradually break down and the paper becomes weak, brittle,and discolored. Much of the paper produced today has a life expectancy of less than fiftyyears, unlike the handmade paper produced three hundred years ago, much of which isstill in very usable condition today.

Acidity and alkalinity are measured on the pH scale (see Figure 3-8).10 This is anarbitrary numerical scale ranging from 0 to 14, 7.0 being the point of neutrality. Allnumbers above this point represent increasing alkalinity, and all numbers below 7.0 indi-cate increasing acidity. Since the scale is logarithmic, each numerical whole unit representsa ten-fold change in acidity or alkalinity. Thus, a pH of 5 is ten times more acidic than a pHof 6, and a pH of 4 is one hundred times more acidic than a pH of 6. While the greatestconcern is for acidity in paper, brought about by modern manufacturing processes and theenvironment, high alkalinity-pH 11 to 14-is potentially equally destructive. Consider, forexample, the effect of a strong alkali such as sodium hydroxide (lye) that is used to pulppaper for testing purposes. Although the chemical reactions are different, both strong acidsand strong bases are damaging. Acid hydrolysis leads to chain breakage and a loss in thedegree of polymerization in the cellulose molecule, while strong bases cause the chains to


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break or shorten from the ends rather than the middle.The concepts of paper permanence and durability developed as efforts were made to

produce papers that were free of acid and that would resist the effects of aging. William J.Barrow was a leader in research and development in this area; the reports of the W. J.Barrow Research Laboratory (see Bibliography, Appendix B) document his pioneeringefforts. Permanence relates to the chemical stability of paper and its ability to retain initialchemical properties over time. Durability relates to the degree to which paper retains itsoriginal strength, especially under conditions of sustained use. A paper may be permanent(i.e., chemically stable) but not durable, and vice versa. It is possible to produce paper thatis both permanent and durable by controlling the following factors: quality of source fiber;fiber length and degree of fiber-to-fiber bonding; contamination of the pulp by residualchemicals, bleach, metals, and other impurities; pH; and sizing. Groundwood papersshould be avoided when creating archival records, for preservation applications (such asfolders, interleaving sheets, or photocopies), or for any paper that must sustain heavy use.

As discussed previously, the chemical properties of paper greatly affect its quality andpotential for long-term preservation. Some of the paper types described briefly below aremanufactured today to specifications that result in permanent paper that is ideally suitedfor archival and preservation applications. Acid-free and alkaline papers made from fullypurified pulp should be specified for all preservation applications, including all papersupplies coming into direct contact with archival records (such as folders, envelopes,

sleeves, interleaving sheets, cross-reference forms and other administrative inserts).Archivists also must share their technical knowledge regarding paper, its preservation, andthe economic benefits accruing from using alkaline papers, in order to influence recordscreators to require (via administrative mandate or legislation) that permanent records becreated on alkaline papers.11

Acid-free Paper. Contains no free acids and has a pH of 7.0 or greater. Care is taken inthe manufacturing process to prevent residual acidity. Cotton, chemical wood pulp, orsimilar fibers may be used. Unless treated with an alkaline substance capable ofneutralizing acids, papers that are acid-free at the time of manufacture may become acidicthrough contact with acidic storage materials or atmospheric pollutants. "Acid-free" hasbecome almost a generic term used to denote a broad range of desirable characteristics ofarchival storage materials. While the term is convenient, it is often used casually to imply

that paper and board stock have an alkaline reserve and all other good qualities, whetheror not this is actually the case. The shorthand use of "acid-free" is probably a necessity inmany institutional situations; to instruct staff to use acid-free folders is much easier thanadding a great number of other qualifiers to describe the intended folders more precisely.However, when writing specifications, ordering supplies, evaluating supply catalogs, andwriting internal guidelines or procedures, terminology should be used that preciselydescribes the pH range and other characteristics of the paper and paperboard materialsrequired for various applications.

Alkaline Buffered Paper. Contains an alkaline reserve (an alkaline earth salt likemagnesium carbonate or calcium carbonate) and-for most preservation applications-has apH in the range of 8.5-10.0. The alkaline earth salt counteracts or neutralizes acid thatmight later enter the paper from the surrounding air or nearby acidic materials. Papers

intended to resist acid for a long period should have approximately 2-3 percentprecipitated carbonate by weight of paper. Except when otherwise specified, archivalstorage materials-folders, boxes, wrapping and interleaving papers, etc.-should befabricated from stock having an alkaline reserve.

Due to a desire for increased commercial availability of permanent papers for printingand recordkeeping, as well as to concern for environmental issues (air and waterpollution), agitation for greater production of alkaline papers has increased during the lastdecade.12 Lobbying groups and alliances (composed variously of publishers, librarians,


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archivists, and environmentalists) have been formed to promote this through economic andlegislative means. Creators and custodians of published works and historical materialshave expressed concern about problems associated with acidic papers and the high costs ofpreserving and reformatting information recorded on them (see Figure 3-9). To meet theseconcerns, standards for permanent paper are being developed and legislation has beenpassed establishing a national policy on permanent papers.13

Figure 3-9. This brittle and water damaged paper typifies problems associated with poorquality paper stored under adverse conditions. (Courtesy oftheMinnesota HistoricalSociety.)

Archivists have been actively involved in building awareness of these issues within theirconstituencies, and must continue to make strides to influence change. Legislative bodies atfederal, state, and local levels must be informed of the high costs of creating records onimpermanent materials, and corporate bodies must be made similarly aware. Prospectivedonors of manuscript collections also should be encouraged to use permanent papers asthey conduct their affairs. Since many donors are already convinced of the importance oftheir work and its place in history, they should need little persuasion to use permanentpaper. They will, however, need information on types of paper available and sources ofsupplies.

Types of PaperPaper is available in a wide range of size, weight, color, finish, and texture; each

variety is designed to meet specific writing, printing, artistic, and storage or packagingneeds. Thus, paper of virtually any historical and contemporary type is likely to find itsway into an archives. Handmade papers will be found in repositories that contain materialsdating prior to 1850 as well as contemporary fine press books or works of art on paper.Japanese papers with long, strong fibers are commonly used for mending archivaldocuments; such papers also have been used for woodblock printing and other artisticworks. A wide variety of paper and paperboard is used to fabricate storage enclosures forarchival materials: folders, boxes, sleeves, and envelopes. By and large, however, machine-


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made papers are the prevalent substrate for modern archival records. The following are themost common paper types:

Bond. Strong and durable paper having good writing and erasing qualities, as well asgood printing qualities, as many bond papers have printed letterheads. Commonly usedfor typed manuscripts, correspondence, printed forms, and electrostatic copies. Originallyreferred to paper produced for government bonds and securities.

Carbon Paper. First made in the early nineteenth century by immersing thin paper inoil-based printing ink. The ink was retained on both sides of the paper so that two copiescould be made at once. Carbon paper made to be used with the typewriter (developed inthe early 1870s) was coated with carbon black pigment in oil and naphtha. Later, carbonblack pigments were at times replaced by oil- or wax-soluble coal tar dyes, and more recentcarbon papers contain a pigment or pigment combinations (not always black as the nameimplies), mineral oils, and wax emulsions. The quality of the paper carrier varies, whichaffects the desired properties of firmness, toughness, pliability, and durability. Pigment isimparted to the copy paper by impact or pressure of a typewriter or writing instrument.Carbon copies made with carbon pigment are stable in light but are susceptible to erasingand smudging.

Carbonless Copies. Papers that contain pressure-sensitive recording media thattransfer an image to receptor sheet(s) through pressure exerted by a writing instrument orimpact typewriter or printer. There are both physical and chemical systems, with many

commercial variations, although chemical pressure-sensitive media are dominant. Theseemploy image-forming dye contained in microcapsules that rupture in response topressure and react with chemicals in the receptor sheet to form an image. Carbonless copiescannot be considered permanent.

Coated. Paper that has had a coating (such as clay or other pigments, adhesivematerials, etc.) applied to the core or base paper to improve its finish for printing or otherend use. The core of a coated paper may be acidic, neutral, or alkaline, and one or bothsides of a paper may be coated. Coatings control ink absorption and enhance graphicreproduction, especially with multiple colors and half-tone illustrations. Coatings increasethe opacity and gloss of paper, and alkaline coatings can enhance its preservation. Ifexposed to very damp or wet conditions, coated papers can block-together, which is ofconcern in disaster planning and recovery.

Copying Paper. Thin tissue of the type found in letterpress copy books that is used toreceive copies of text written in copying ink. Paper is unsized and strong in proportion toits weight.

Cover. Heavy paper stock used as covers for pamphlets or brochures to provideprotection for text. Generally strong with good folding qualities.

Decorated. Papers (originally decorated by hand, but now often printed) used forbook and pamphlet covers or endsheets. Marbled, paste, embossed, and stencil papers areoften found in ledgers, journals, and daybooks; quality varies depending upon paper,pigments, process, and skill of the artist. Decorated papers can provide useful bibliographicclues and are a subject of study in themselves.

Kraft. Strong flexible paper made via the sulphate or kraft process. If the pulp isunbleached, the paper is usually light brown in color and is typically used for wrapping

paper, shopping bags, and envelopes. Such paper is durable but not chemically stable.Historically has often been used to wrap or house archival materials, but is not suitable forthis purpose. Fully bleached and purified kraft pulp can be used to make a chemicallystable paper, such as archival bond.

Ledger. Paper originally used for handwritten ledgers and account books; now usedfor printing. Heavily sized (traditionally tub-sized with gelatin), strong, durable, anderasable, with a uniform surface for writing and ruling lines. Also known as account bookpaper.


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Manifold. Thin translucent tissue, which may be glazed, used for duplicating andespecially as interleaving with carbon paper. Term formerly used to refer to "carbonized"paper.

Manila. Originally applied to paper stock made from manila hemp or jute. The termnow refers not to the pulp source (which is frequently unbleached chemical wood pulp),but to paper that has a brownish color resembling that of the original. The term "manilafolder" is often used to refer to commercial or office quality folders that do not meetpreservation requirements.

Newsprint. Generic term commonly used for the type of paper used in printingnewspapers. A soft paper with short fibers, largely composed of groundwood pulp. Notpermanent. Often found in archival holdings as second (carbon) sheets, forms, receipts,invoices, telegrams, pamphlets, and newspapers.

Onionskin. Lightweight, durable, highly glazed, nearly transparent paper used forcarbon copies of typewritten material and for airmail letters. Made from cotton fibers,bleached chemical wood pulp, or combinations.

Parchment Paper. Vegetable or imitation parchment, made by passing unsized paperthrough a bath of sulphuric acid, followed by thorough washing in water, immersion indilute ammonia to neutralize the acid, and sometimes a coating or bath of glycerine orglucose, followed by drying. Strong, durable, translucent paper with a good writingsurface. Often used instead of genuine parchment (made from animal skin) for legal

documents and certificates.Text or Book. Range of papers with varying characteristics (appearance, texture,finish) to meet printing requirements for books. Usually a high grade uncoated paper.

Transparent or Tracing. Thin paper with ahard, smooth surface having excellent optical transmission properties. Prepared tracingpaper is made by impregnating paper with gums, oil, and/or resin to transparentize it.Natural tracing paper is made by highly beating the fiber during the papermaking processto increase its surface area, then compressing and compacting the formed sheet. Preparedtracing papers may become brittle and discolored as they age, while modern naturaltracing papers, which are free of impregnating agents, tend to remain in good condition.

Colored Papers

Colored papers contain dyes or pigments to achieve the desired shade and hue, orthey may be naturally colored as a result of the stock material used. (Dyes are also used toalter the natural tone of the pulp to achieve the desired shade of white in the finishedpaper.) Dyes are usually added to the pulp in the beater, or they may be added to thesurface of the finished sheet in a suitable medium. While it is possible to achieve coloredalkaline papers, there are inherent limitations because some dyes will function in the acidrange; but not in the alkaline. Also, the calcium carbonate in alkaline papers tends to makethe colors less intense.

The three types of soluble dyes are acid, base, and direct. Since they vary in theiraffinity to cellulose fibers, various systems are used to retain them (such as alum and sizeor a mordant containing tannic acid). Generally, acid dyes achieve less brilliant shades than

basic dyes; both are usually fugitive to light. Direct dyes have a great affinity for celluloseand do not require a mordant (fixative); while their shades are somewhat dull, they arerelatively lightfast. Finely divided pigment particles (which do not dissolve) are retainedon cellulose fibers with the aid of alum. Inorganic pigments, such as Prussian blue orcarbon black, can be used to achieve colors that are lightfast.

Preservation problems posed by colored papers relate to potential acidity, degree oflight or colorfastness, and degree of solubility if exposed to water. It is safe to assume thatmost colored papers currently found in archival holdings are not very stable for any


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combination of the above reasons. Information recorded on colored paper can be difficultto duplicate because of limited contrast between the text orimage and the background.Record materials (such as colored writing paper) should be protected from exposure tolight, while internal archives forms printed on colored stock should be replaced by paperstock of known stability that is alkaline and that contains no colors that will bleed or fade.

Unstable Copy Papers

Many techniques have been used over time to generate copies of written or graphicmaterial as a means of disseminating information. Such copies may eventually find theirway into archival and manuscript holdings, where they reside-for all practical purposes-asthe copy of record, even if they were created by impermanent processes for ephemeral pur-poses. Copy stability relates to three factors: quality of the paper used, stability of themedium, and adhesion of the medium to the paper. As with most technical innovations,quick copy processes were not created with a view to long-term permanence. Therefore, ar-chivists must be able to recognize the dominant copying processes and initiate steps topreserve their informational content. The processes described below are commonly foundin archival holdings and represent classes of similar processes that were marketed undervarious trade names.14

Gelatin Dye Transfer. Employs a light-sensitive matrix (gelatin containing dye and

developed silver halides) from which prints are obtained by physical transfer. Copies aremade by exposing the matrix in direct contact with the document to be copied, activatingthe exposed matrix in an alkaline solution, and transferring the image to copy paper via aroller or squeegee. Copy paper is uncoated, but absorbent to allow it to take up image dye.Image tone is dark grey at maximum density but changes to brownish grey. Copies arerelatively stable.15 Example: Verifax1i> (Eastman Kodak Company).

Thermographic. Employs heat-sensitive coated paper, with which text to be copied ISexposed to infrared radiation. The text, which must be recorded in a pencil or inkcontaining carbon or a metallic compound, absorbs infrared radiation. The heat is sufficientto convert the chemical compounds in the sensitized paper, forming a visible imagecorresponding to the text. Thermographic papers continue to be heat-sensitive and willdarken with age and exposure to elevated temperatures. Example: Thermo-Fax (3M

Company; introduced in 1950; produced only letter and legal size copies).The above copying processes, which were designed for making single copies or amodest number of multiples, may be contrasted with duplication or edition processes. .

Mimeograph. Stencil duplication. The stencil is typewritten or cut by hand with a stylus,and then printed using a rotary-type duplicating machine. The mimeograph image isgenerally black, but other ink colors can also be used. Stability is related to paper quality;image quality is sometimes poor depending. upon crispness of stencil and quantity of inkemployed. Example: Mimeograph (A.B. Dick Company); but the term has taken on genericconnotations.

Hectograph. Spirit duplicating. The image is typed or drawn on a carbon master.Copies are produced by solvent action and pressure on a press that moistens the surface ofthe copy paper and brings it into contact with the carbon master. A thin layer of carbon

from the master is thereby transe_rred and adhered to the copy paper. Since the masterbecomes depleted, each edition is limited to about 500 copies. Image color of copies ispurple. Trade names: Ditto, Speedograph.

Xerographic Copies

The first commercial xerographic copier was introduced in 1959-60 by the Haloid (nowXerox) Corporation, based on the work of the inventor of xerography, Chester F. Carlson,


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and others. Xerographic copiers produced by many companies have proliferated sincethen, with an ever greater number of copies finding their way into archival repositories.16

Typically, xerographic copies are made on a bond paper of any color; for permanent copies,the paper must be alkaline and carbon black toner must be completely fused to the paper.(See section on "Photocopying," Chapter 9.)

Also called the transfer or indirect electrostatic process, xerography (formed from theGreek words for "dry" and "writing") is based on the principles of static electricity-that is,materials having opposite electrical charges attract while materials with the same chargerepel.17 Xerography employs selenium (or other photo conductor material), which iscapable of holding an electrostatic charge and dissipating it upon exposure to light. Aselenium coated surface (drum or plate) is given an electrostatic charge and then, via a lenssystem, exposed to a projection of the document to be copied. Upon exposure to light, theelectrostatic charge remains only in the image areas (electrostatic latent image). Developer,a fine powder that consists of a carrier (minute spherical particles or beads composed ofmagnetized iron, steel, or iron oxide, with a polymer coating on the surface) and toner, athermoplastic pigmented powder (usually carbon black dispersed in a resin binder), iscaused to fall evenly over the charged surface where it clings by electrostatic attraction tothe image area. The carrier does not become part of the final toner image, but is simply aphysical vehicle to disperse the toner particles, and is reused. Uncoated (plain) paper isgiven a positive electrostatic charge, which attracts the toner. The thermoplastic toner is

then physically fused to the paper by heat and/or pressure, causing it to adhere and fix theimage to the paper. This basic technology is realized in many commercial xerographiccopiers that use a variety of photoconductors and toner systems.

Color xerography employs the same charge-expose-develop process, but rather thancarbon black, it uses color developer materials (pigments or dyes, or a mixture of the two,in a thermoplastic polymer). Since this technology is proprietary and is changing sorapidly, there is no way to predict the stability of color xerographic images found inarchival holdings. Complicating the issue is the fact that what may appear to be a colorxerographic copy may in fact be produced by some other non-impact imaging process,which cannot necessarily be considered permanent. All materials of suspect stabilityshould be copied onto alkaline paper using the xerographic process with carbon blacktoner.

Facsimile Copies

Capabilities for telefacsimile (fax) transmission are proliferating in offices everywhere,and fax copies, like their historical counterparts, are beginning to appear in archivalcollections. This is yet another area where technology is rapidly changing and commercialsystems are competing to meet immediate needs for information. The first facsimiletransmission was achieved by an American, Alexander Bain, in 1842, while the precursor tocontemporary fax machines was invented in 1850 in England by Frederick Bakewell. In1922, a machine similar to Bakewell's was used to transmit pictures over Western Uniontelegraph lines; in 1971, the first modern facsimile machine, the Xerox Telecopier, wasintroduced.18

Telefacsimile machines transmit an exact copy of a document, in a matter of seconds,over standard telephone lines, where it is received on another machine. At the transmittingend, a scanner reacts to light and dark areas on the paper by generating correspondingelectronic pulses that are transmitted; at the receiving end, another facsimile machineconverts the pulses to signals that activate a printing device. Obviously, commercialpriorities relate to speed and quality of transmissions, not to possibilities for longtermretention of the copies generated.

The three most common non-impact printing technologies for facsimile copies are:


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thermal printing on paper with a heat-sensitive coating, thermal transfer printing on paperusing a pigmented medium that is transferred from a ribbon by heat, and electro-photographic printing on paper using an electrostatic charge to transfer the pigmentedmedium which is then fused by heat. Thermal facsimile copies (as opposed to plain paperelectro-photographic copies) are currently dominant due to their lower cost. They aresensitive to heat and light, can react with chemicals typically found in an officeenvironment (such as markers, hairspray, and polyvinylchloride [PVC] plastic folders), andcontain impermanent dyes. For these reasons, text on thermal copies is likely to fade,become illegible, and/or the paper may darken overall in a relatively short period of time.They cannot be considered permanent. While the paper quality of electrophotographiccopies should be satisfactory, the adhesion of the image to the paper, and thus its long-termstability, is unknown. Given the difficulty of differentiating between potentially stable andunstable facsimile copies, all should be photocopied onto alkaline bond paper.

Inks and Other MediaA variety of ink types are encountered in archival and manuscript holdings. Inks have

been made for centuries, either by hand or commercially manufactured, for variouswriting, drawing, recording, and printing purposes. Qualities and characteristics of inksvary depending upon their composition and method of formulation. Very simply, inksconsist of pigments or dyes (to impart color) in a carrier or vehicle (to transmit and adhere

color to paper); various additives affect fluidity, speed of drying, penetration, and otherrequirements of specific inks. The degree to which various inks are stable (chemicallybalanced, lightfast, soluble, acidic, etc.) will have a bearing on their long-term effect onpaper and should affect decisions regarding exhibition, treatment, and housing of recordmaterials. Archivists thus should be aware of common inks and their characteristics,although inquiry in this area is complicated by several factors. Commercial formulations ofinks are not static and there is some tendency toward industry reticence on the entiresubject (see Figure 3-10). In addition, there has been little research undertaken that bearsdirectly on specific archival concerns. Since the possibility of definitively identifying agiven ink on paper is limited at any rate without analytical means, archivists shouldapproach all inks as though they may be vulnerable in various situations. For example, it isappropriate to assume that all inks have the potential to fade if overly exposed to light, and

that all inks have the potential to bleed or transfer if exposed to moisture.


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Figure 3-10. Unfortunately, records carved on stone do not last forever and not all inkssurvive the ravages of time, despite manufacturer's claims. (Courtesy ofthe author.)

Carbon Inks. The earliest inks (sometimes known as India or Chinese ink) were madeof carbon soot mixed with a glue size and molded into sticks. A stick would be dissolved inwater for use as ink, usually applied with a brush. Fluid carbon inks are suspensions oflampblack or ivory black in water and gum arabic (a water-soluble binding agent obtainedfrom the acacia tree). Carbon inks were used widely until the nineteenth century (with quillpens) and are still used today primarily for calligraphy and art work. In their purest form,carbon inks are permanent, lightfast, and nondamaging to paper.

Iron Gallotannate (commonly called iron gall) Inks. Made by combining ferroussulphate (copperas) with gallic and tannic acid derived from nut galls. The liquid wasthickened with gum arabic to give the ink enough body to flow properly from a pen.Initially, the ink is almost colorless on paper, but upon exposure to air, it oxidizes and

becomes dark. In this chemical reaction sulphuric acid is formed. An especially acidic inkcan "burn" into paper, 'resulting in a lacy effect where the paper is perforated or exhibitslosses. By contrast, some inks are less acidic and fade over time. One reason for this is theuse of insufficient quantities of gallic and tannic acids in the ink formulation. (Theformulation of ink was not scientific, due to a lack of analytical techniques for determiningthe chemical composition of the components. In addition, individuals compounded theirown inks, using a variety of home formulas that incorporated such ingredients ashydrochloric acid, wine, and vinegar.) Today, iron gall inks may range in color from darkblack to light brown. Many are still quite legible. The manner and rate in which iron gallinks age depend on the formula used to make the ink (and therefore the degree to whichthe ink is acidic), the concentration of the ink on the document, the quality of the paper,and the conditions under which the paper has been stored. Iron gall ink was important to

Europeans because it had a good "bite" on vellum and parchment and, therefore, could notbe erased or removed easily without leaving evidence of the alteration. Iron gall inkcontinued to be used after the introduction of paper, despite the fact that it was lesssuitable for this material. In the United States, iron gall inks were used almost exclusivelyduring the seventeenth and eighteenth centuries. Iron gall ink was sometimes reduced to apowder and reformulated with water as needed.

Copying Inks. Inks that allow a direct offset copy to be made from an originaldocument. Many inks will produce a "copy" if a damp sheet of paper is pressed against the


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original document soon after it is written and before the ink thoroughly dries, although-due to transfer of color from the original to the copy paper-only a limited number of copiescan be produced before the legibility of the original is affected. Therefore, iron gall inksmade especially for copying documents onto thin moistened paper in a letterpress bookbecame common in the 1870s. Such inks were formulated with sufficient colorant to pro-duce multiple, legible copies without diminishing the original, and dextrin or gum arabicwas added to assist in adhering the ink to the copy paper. To keep these concentrated inksfrom drying out too quickly, glycerine or some other humectant was added. Copying hadto occur before the iron gall ink completely oxidized and became insoluble. Iron gall ink towhich soluble dyes (like the soluble blue aniline dye developed in the early 1860s) wereadded could produce copies even after the ink completely oxidized. A press copy containsbut a small part of the color from the original document; the image is more intense on theback of the tissue (which was in direct contact with the original) than it is on the front (fromwhich side the image is read).

Modern Manuscript Inks. Early fountain pen inks were essentially iron gall inksmade with less iron content and more dyes (originally vegetable dyes). Thickeners such asglycerine were added to insure that the ink would flow properly from a pen. Since theintroduction of aniline dyes in the 1860s, most inks have been made from synthetic dyes,generally as aqueous solutions with preservatives and thickeners added to make the inksufficiently viscous. While stability has improved, most inks made with synthetic dyes tend

to be acidic and impermanent.Porous Pens. Known variously as felt-tip and fiber-tip pens and "magic markers"; penpoints have been made from such materials as tightly glued plastic spheres or filamentsand treated bamboo. The inks used in such porous pens are water- and/or solventsoluble(depending on the material needed to dissolve the dye) and are usually highly susceptibleto feathering or bleeding if exposed to water or moisture. They are generally notpermanent, are often acidic, and-depending upon the color-are quite fugitive uponexposure to visible light and ultraviolet radiation. Such temporary markers consist usuallyof synthetic dyes dissolved in a mixture of isopropyl alcohol and water, although morestable pigment pens are now available.19 "Permanent" markers (capable of writing on suchsurfaces as plastic and metal as well as paper) consist of dyes dissolved in a solvent(usually xylene). The current widespread use of porous pens and markers has implications

for archives wishing to exhibit records written or signed in such inks; and archives staffshould be prohibited from using such writing instruments when labelling boxes and filefolders.

Printing Inks. Traditionally made of carbon or lampblack (soot) in boiled linseed oil,which hardened or dried by oxidation. These inks produced a very stable permanentimage. Modern printing inks often contain both pigments and dyes, may substitute mineraloils for the more costly linseed oil, and utilize drying agents to speed up oxidation, whichis necessary for modern high-speed printing processes. They are less permanent than earlyprinting inks, which had no unstable additives. Printing inks vary widely in quality andare manufactured to have different properties (such as viscosity, rate and method of dry-ing) for various printing applications.

Typewriter Ribbon Inks. Pigments or dyes in a slow-drying oil carrier; they dry by

absorption into the paper. Fabric ribbons that carried the ink in a typewriter replaced earlymethods of inking that brought the type into contact with inking pads or inking rollers.Ribbons were made of silk or cotton; the inks were composed/of carbon black, dyes, or amixture in an oil carrier. Modern ribbons are made from fabric or plastic, and the inks arecombinations of pigments, dyes, solvents, fatty acids, and a wetting agent. Conventionally,an image is transferred via impact of the character against an inked ribbon into paper (seeFigure 3-11). Typewriter inks that can be lifted off by correcting ribbons are made withfewer solvents and oils, so that the ink remains on the surface of the paper and is not easily


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absorbed into it.

Figure 3-11. Typewriters were once hailed as a technological wonder. (Courtesy of MoonRabbit'M Post Cards.)

Non-impact Printing Inks. A wide variety of proprietary inks are used in non-impactprinting processes that create computer hard copy.20 In liquid ink jet printing, a stream ofink droplets is released from a nozzle and deposited on paper (or other surface) to form animage. Non-impact printing inks, which are generally aqueous, contain dyes, binders,

humectants, defoamers, solubilizing agents/dispersants (to keep nozzles from clogging),and corrosion inhibitors, among many other substances. In addition, bubblejet inks(thermal inkjet technology) must be able to withstand temperatures over 300C. Solid (hot-melt) ink jet inks have also been developed that are solid at room temperature but liquid atoperating temperature; they are extremely fast drying. Specially coated paper is required toachieve high quality ink jet prints, although it is possible to print on non-coated but heavilysized paper. Stability of non-impact printing inks is unknown.21

Ballpoint Pen Inks. Developed for commercial use by the 1930s and originallycomposed of dye dissolved in an oil base, which dried by absorption of the oil into thepaper. These early inks were retained on the surface of the paper and had a tendency tosmudge. Contemporary quick-dry or glycol inks consist of colorants (soluble dyes orinsoluble pigments) in an alcohol solvent base with other additives (such as polyethylene

glycol) that control the viscosity of the ink and its ability to turn the ball bearing in thepoint socket. Glycol inks dry by absorption into the paper and evaporation of the solvent.Metalized dyes are used that are lightfast and highly solvent-soluble. Water-based inks forballpoint pens are also made that flow well from the pen and dry quickly. They containwater soluble dyes or water dispersable pigments, water, wetting agents, gums, and asolvent that helps the ink to dry more quickly.

Graphite. Graphite is a naturally occurring crystalline form of carbon, which is alsomade artificially by a furnace process. For use in pencils, pure graphite with some added


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clay is consolidated and hardened by firing at high temperatures. It has been confused withlead (also used as a writing material); thus graphite is commonly referred to as a "lead pen-cil" Graphite is chemically stable but capable of smudging; not affected by exposure tolight.

Animal SkinsLeather, parchment, and vellum are made from animal skin that is treated in a series of

complex steps to make a stable and durable material used for a variety of purposes.Archival repositories contain parchment used as surfaces for printing and writing, as wellas many types of leather used as book coverings or fabricated into clothing or functional ordecorative objects.

Vegetable tanned leather was the most common covering material for books until thenineteenth century. During processing, skins are taken through a series of steps to removethe outer layer of the skin, hair, grease, and other unwanted material through scraping andsoaking in chemical solutions. The skins are then chemically stabilized, or tanned, withvegetable tannins (obtained primarily by cooking tree nut galls in water) to prevent decay.The most stable leathers were produced through the sixteenth century by a slow tanningprocess that left protective salts, known as non-tans, in the skins. These early vegetabletanned leathers were resistant to decay and acid deterioration. During the late seventeenthto the nineteenth centuries, the demand for leather increased and shortcuts were

introduced into the tanning and dyeing processes; they introduced strong acids to speedup the processes and also eliminated the beneficial non-tans that protected the leather fromacidic decay. The resulting leathers quickly deteriorated because of residual sulphuric acid,which was present in the skins as a result of the manufacturing process or was absorbedfrom the environment.

Leather is naturally acidic by virtue of the tanning process. However, excessive acidityin leather results in a condition known as "red rot," which eventually can cause leather tobecome hard and brittle so that it deteriorates to a crumbly reddish-brown powder. Leatherin such a state cannot be restored or revitalized. For many years, the most satisfactoryleather for bookbinding and conservation was considered to be that meeting therequirements of the test developed by the Printing Industries Research Association of GreatBritain (PIRA), which determined the resistance of vegetable tanned leather to sulphur di-

oxide in the air. However, research has shown that there is little correlation between theleather's actual performance and the performance predicted by the PIRAtest.22

Many bound volumes in archival collections are covered partially or fully in leather:account books, ledgers, diaries, and presentation volumes in particular. Leathers thatcommonly have been used for bookbinding include:

o Calf-Used predominantly until the end of the eighteenth century. Calf has littlenoticeable grain and thus is easily decorated. The surface of calf is delicate and soft;it readily scratches and mars. Calf is often found on account books and ledgers aswell as on sets of law books.

o Goat-Soft, pliable, and strong. The grain is distinctively textured with small ridgesand furrows in an all-over pattern. Goatskin has traditionally been used for fine

bookbinding since the seventeenth century. It is also known as levant, niger,morocco, and oasis.o Pigskin-Strong and durable; suitable for large books. Hair follicles, which are

arranged in triangular groups of three, create a distinctive grain pattern, which is anidentifying characteristic.

o Sheepskin-Soft, porous leather, usually grained to imitate higher quality and moreexpensive skins. Not very strong. Natural colored "law sheep" was used to cover lawbooks.

o Suede-Leather (calf, goat, etc.) that has been buffed on the flesh (inner) side to


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produce a nap. Often used for blank books in the nineteenth century.The process of chrome tanning was developed in 1858. It is essentially a chemical

process by which skins are treated with basic chromium sulphate. While durable, chrometanned leathers are not very supple (and thus resist such bookbinding procedures asturning-in, or wrapping the leather around the edges of the boards to the inside). They alsoresist embossing and gold tooling. Chrome-tanned leathers are used for fine binding inFrance, but are not used extensively in the United States.

Vellum and parchment were used extensively in the Middle Ages as writing surfacesfor manuscripts; vellum also has been used since this period as a covering material inbookbinding. Traditionally, true vellum is the unsplit skin of a young calf, whileparchment is made from split sheepskin. The method of producing both is the same,however. Skins are preserved by soaking them in a lime (strong alkali) solution, cleanedand scraped to remove the hair, and dried under tension on a wooden frame. While stillunder tension, skins are smoothed or finished by shaving them with a knife and rubbingthem with pumice. Today, both vellum and parchment are made from the skin of any smallanimal, such as calf, sheep, or goat. Both skins are strong and long lasting (due in part tothe lime, which is not removed during processing); they also are very reactive to changes inthe moisture level. They will cockle (contract to form wrinkles and puckers) whendampened and allowed to dry without restraint, and many books covered in vellum havewarped boards as a result of changes in the relative humidity.

Vellum and parchment are not in common use today in the United States, except byartists and book conservators (although parchment is occasionally used for legaldocuments and certificates). These skins will be found, however, in archival collections thatcontain early manuscripts and legal documents, as well as in college and universityarchives that have parchment diplomas (the proverbial sheepskin). Both skins appearsmooth and hard; depending on thickness, they may be translucent or opaque, with a colorranging from creamy white to ecru. Vellum and parchment can be stained any color, butusually are not; many skins have faint vein and hair markings. It is difficult fornonspecialists to differentiate between parchment and vellum, and parchment is the termoften used generically to refer to either material. What is most important in an archivalcontext is to recognize that a material is either parchment or vellum, as their handling andtreatment needs are the same.

Tawed skins may appear in some repositories, especially on seventeenth- oreighteenth-century books. Tawed skin is not tanned (and thus, like vellum and parchment,is not leather), but is preserved in solutions of alum and salt (and sometimes other mate-rials, such as egg yolk or flour). After air drying, the skin is flexed over a blade to soften it.Tawed skins (generally pigskin and goatskin) are tough, flexible, and usually white inappearance; they are used today primarily for conservation bindings.

TextilesA variety of textiles may be found in archival collections, including flags, needlework,coverlets, uniforms, ribbons, dresses, and other types of clothing and accessories. Suchitems, especially if they have had an active life of normal use, may be weak, damaged, anddirty. No attempt should be made to clean textiles. They require special care and storage

(separate from other archival materials), and advice should be sought from a textile curatoror conservator.

Other textiles that may be found in archival collections include linen-which was oftenused as a support or backing for maps and architectural drawings-as well as silk, cotton,and muslin-all used as linings to support fragile paper documents (see Figure 3-12).


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Figure 3-12. Although tracing cloth (architectural linen) is a stable support, it must be keptaway from moisture because of its starch coating. (Courtesy ofMoon Rabbit TM Post Cards.)

Book cloths are likely the most common textiles found in archival holdings.Historically, a number of fabrics have been used to cover books, including silk and velvet.Calico came into use as a book cloth in England in the 1820s; early book cloth was starch-filled muslin that was colored and glazed. Since then, different materials and coatings havebeen used to make book cloth, and various finishing techniques have been employed (oftenpassing the finished cloth through engraved rollers) to impart the desired pattern and

texture to the cloth. Book cloth is sometimes embossed to imitate leather, and care must betaken to properly identify the covering material so that appropriate cleaning and treatmentprocedures are applied. Buckram is a heavy book cloth made from either cotton or linen;the term formerly referred to starchfilled cloth but now is used also for pyroxylin coated orimpregnated cloth. Book cloth, which is available in a wide variety of types and weights, isclassified as follows by the coating material used.

o Starch-filled-Still in use today. Chemically stable but not durable; susceptible toabrasion, insect damage, mold, water spotting, and soiling. Easy to use andaesthetically pleasing. A slurry of water, starch, and clay is added to pigment(s),cooked, and then applied to the cloth.

o Pyroxylin-treated-Thebase of the coating is cellulose nitrate (also known asnitrocellulose or gun cotton). Pyroxylin compound is composed of gelatinizedcellulose nitrate, a plasticizer, pigment, and an organic solvent. Pyroxylin treatedfabrics were introduced in the late nineteenth century; in 1922 DuPont introducedpyroxylin filled or impregnated cloth. Though it is relatively durable, pyroxylintreated cloth may stiffen in low temperatures and may become tacky in hightemperatures. It is "washable" (i.e., can be wiped with a damp cloth), and is resistantto moisture and insects, but-given the presence of cellulose nitrate-pyroxylin treatedbook cloth is not as stable as starch-filled cloth.

o Acrylic-Chemicallystable and resistant to moisture, mold, and insects. Not yet in


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common use and durability not tested. Environmentally, better than pyroxylin sinceproduction is water-based rather than solvent-based.

Photographic MaterialsPhotographic images are formed by the action of light on chemical compounds. Very

simply, a photograph (print, negative, or positive transparency) may be defined as asupport upon which an image-bearing layer is applied. The most common binder in whichparticles that make up the image resides is gelatin; however, albumen and collodion were

common binders used in the nineteenth century. The image in most black-and-white printsis finely divided metallic silver, but other final image materials include platinum,pigments, and dyes. There are a number of possible support or base materials, includingmetal, glass, paper, and plastic film (cellulose nitrate, cellulose acetate esters, andpolyester). Various layers (such as anti-curl and anti-abrasion layers), adhesives, coatings(such as wax or varnish), and applied color may also comprise the structure of aphotograph, depending upon the particular process and its date and place of fabrication.The baryta layer, which rests between the binder and the paper support on some prints,provides a consistent surface for the emulsion and also contributes reflectance to the image.

As photographs have evolved from relatively simple structures made essentially byhand (typified by salted paper prints) to contemporary manufactured materials, they havebecome progressively more complex. Thus, problems with or failure of any of the

component elements can mean damage to or loss of the image. For example, not only maythe image bearing layer be susceptible to such damage as fading, scratches, flaking, orstaining, but the support may fail (i.e., glass may break or plastic may shrink).

Long believed to be inert and chemically stable, glass is in fact subject to deteriorationdepending upon its chemical composition. Under conditions of high relative humidity,unstable photographic glass supports are subject to corrosion, which can cause softening ofthe emulsion and varnish layers as well as image fading. The glass/emulsion interface isphysically vulnerable to low relative humidity, which can result in tension between the twolayers and eventual lifting or delamination of the gelatin emulsion as it contracts.23

Historically, fine paper (such as writing paper) has been used for photography.Contemporary photographic papers, which are manufactured to exacting specifications tomeet processing and finishing requirements, are high in alpha-cellulose content andcontain no metallic impurities. Thus, support papers are extremely stable and do notcontribute to image degradation. Resin-coated (RC) papers, which are coated on both sideswith polyethylene, were introduced in the 1960s. Unlike "fiber-based" papers, which canreadily absorb processing chemicals, RC papers inhibit or control absorption and thus pro-cessing times are reduced. Early resin-coated papers tended to develop cracks in the plasticcoating that disrupted the image; although the stability of more recent RC papers hasimproved, they do not yet meet requirements for archival purposes.

Cellulose nitrate film, introduced for commercial use in 1889, was manufactured invarious roll and sheet formats until the early 1950s. It is inherently unstable, flammable,and emits oxides of nitrogen, which, in the presence of moisture, convert to nitric acid asthe film deteriorates. Beginning in the 1930s, cellulose nitrate film was gradually replacedby various cellulose ester safety films (diacetate, triacetate, acetate propionate, acetatebutyrate). While the flammability problem of nitrate was solved, some cellulose ester filmshave proved to be chemically unstable. Many cellulose acetate esters shrink as they age,causing distortion and buckling of the emulsion; acetic acid is among the by-products oftheir deterioration (see Figure 3-13).24 Cellulose triacetate is the most common film basemanufactured and used today. Until recently it was thought to be chemically stable, butthere is increasing evidence that it does not have good long-term keeping properties.Periodic inspection of archival holdings of cellulose triacetate film is recommended, and,when undertaking negative duplication projects, polyester film should be specified.25


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Polyester (polyethylene terepthalate) is dimensionally and chemically stable and shouldsupplant cellulose triacetate film in all archival applications.

Figure 3-13. These two cellulose diacetate film negatives exhibit early and advanced stagesof fissuring that exemplifies the deterioration of this material. (Courtesy ofSarah S.Wagner.)

The long-term stability of photographic materials relates to a number of interrelatedfactors: 1) the inherent stability of the component materials; 2) the quality of original

processing, including proper or improper fixing and washing; 3) exposure to an uncon-trolled environment, including high temperature and relative humidity, light, andpollutants; 4) physical and chemical suitability of enclosure materials; and 5) handling anduse procedures. Photographs are extremely sensitive to adverse environmental conditions.The laminate structure of most photographic materials makes them susceptible tofracturing, splitting, or extreme curling as disparate materials (such as gelatin or albumenon a thin paper support) respond differently to changes in relative humidity. Image silveris degraded by exposure to oxidizing gasses and atmospheric moisture, which can result inimage discoloration, fading, and "silver mirroring" (the appearance of a metallic blue sheenon the surface of a photograph). Residual processing chemicals (thiosulphate complexes)also react with image silver and can cause yellow and brown staining. Exposure toadhesives (especially those containing sulphur) and poor quality enclosures and mountsalso can result in image staining. All of these reactions are exacerbated by elevatedtemperature and relative humidity. Such conditions will also accelerate the rate of deterio-ration of chemically unstable materials, such as cellulose nitrate and cellulose acetate films.

Most archival repositories possess a diverse sampling of photographic materialsrepresenting the entire range of the technological development of photography, from thedaguerreotype (announced to the world in 1839) through present color processes. Archi-vists must be able to recognize the dominant types of photographs in order to care for themproperly. Preservation of photographs involves responding to the physical needs of the


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format and structural materials, as well as to the requirements of auxiliary or secondarymaterials such as mounts, cases, and albums, which are integral to the photographic record(see Figures 3-14, 3-15). The creation of preservation reproductions (duplicates and copies)of inherently unstable as well as frequently requested images plays an important part indeveloping a preservation program for photographic materials.26

Figure 3-14. This original presentation mount has artifactual and association values thatrender it worthy of retention, although for preservation purposes it might be appropriate tostore it separately from the photograph. Note deterioration across the upper third of theimage caused by writing that is coming through from the back of the photograph.(Courtesy of the Library ofCongress.)


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Figure 3-15. The intrinsic value of this Potter Palmer real estate album containing albumenprints renders it necessary to retain it in original format. (Courtesy ofthe Chicago HistoricalSociety.)Adhesives

Adhesives are organic or synthetic substances that are capable of holding two surfacestogether by achieving an appropriately strong interface between the two surfaces (i.e.,adherends) through chemical and/or mechanical means. Adhesives vary in theircomposition, setting characteristics, bonding strength, flexibility, aging characteristics, andreversibility. Fillers, extenders, plasticizers, hardeners, anti-oxidants, preservatives, and-inthe case of animal glues-even perfumes to mask unpleasant odors, are among the manyadditives employed to achieve desired properties. There are many classes of adhesivetypes, and a great variety of adhesives specifically formulated for different end purposes,from mending paper or china to joining aircraft components. The degree to whichadhesives are stable and capable of retaining their original characteristics over time relatesto their composition and the conditions to which they are exposed.

Adhesives are a concern in archival settings for several reasons. First, they are oftenmisapplied and thus cause damage to a wide variety of materials (see Figure 3-16). Well-meaning people mend treasured letters and photographs with pressure-sensitive tape, ' forexample, and scrapbooks often seem to be virtual catalogs of every known adhesive.Adhesives may break down over time, losing their adherent properties; they also maypermanently stain documents and initiate harmful chemical reactions that hasten thedeterioration of paper (see Figure 3-17). Archivists must contend with these problems andalso ensure that only appropriate adhesives are used in conjunction with records in the

context of conservation treatment, exhibit preparation, and for fabricating enclosures andhousings for archival records.Adhesives used to construct housing must be suitably strong, chemically stable, and

incapable of initiating chemical reactions that could have an adverse affect on archivalrecords with which they are in proximity. However, such adhesives should not, byextension, be considered suitable for direct application to record materials. Each adhesiveand adhesive application must be evaluated individually. Adhesives should never beapplied directly to (nor removed from) archival records except by a qualified conservatorduring the course of conservation treatment; adhesives used in the context of treatment are


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evaluated in terms of their composition, physical and chemical stability, aging properties,strength, flexibility, color, and reversibility. Adhesives should not be applied directly torecords during the performance of preservation tasks. There are many nonadhesivepreservation options available to protect and support weak or damaged materials, as wellas many ways to avoid adhesive contact with records in exhibit preparation and mounting.Such approaches will be covered in the following chapters.

Adhesives are applied in a fluid state and cure or set by converting to a solid orhardened state. Adhesives can be described by their setting characteristics:o Cooling of a thermoplastic-Adhesives that will repeatedly become soft and pliable when

heated and will harden and set upon cooling without any change to their inherentproperties, and that thus usually remain soluble. Commonly (but inaccurately)referred to as "heat-setting." Includes waxes, resins, some classes of acrylics, and"heatset" tissue.27

o Release of solvent-Starches (vegetable pastes), dextrins, protein glues (hide, bone, fish,gelatin), polyvinyl acetate emulsions, acrylics, and natural and synthetic rubber. Theadhesive component is in a water or organic solvent carrier that evaporates, leavingthe adhesive layer.

o Chemical reaction (polymerization in situ)- Thermosetting adhesives, including epoxies,polyesters, urethanes, and some classes of rubber-based adhesives. Bonding occurs

when two reaction-sensitive adhesives are brought into contact with one another withapplied or contact pressure.


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Figure 3-16. Band-aids were used creatively-if inappropriately-to cover sharp fasteners onthis volume. To make the problem more interesting, the paper label referring to the Band-aids was attached with pressure-sensitive tape! (Courtesy ofthe National Archives and Records

Administration.)


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Figure 3-17. Pressure-sensitive mending tape has caused embrittlement and disfiguring

staining of the paper. (Courtesy of the Minnesota Historical Society.)

o Pressure-sensitive-Adhesives that will adhere to a surface by means of slight pressure atroom temperature, such as cellophane tape, masking tape, and "archival" mendingtape. Any of a number of adhesive types (including classes of acrylics and rubber-based), generally on a cloth, paper or plastic film carrier, that is thin, flexible, andconforms to the surface to which it is applied. Unlike other adhesives that harden,pressure-sensitive adhesives remain permanently tacky and have relatively low bondstrength. Depending upon the adhesive and its formulation, the carrier often fallsaway or can be easily removed, while the adhesive mass is often difficult to removeand can cause permanent staining of the paper or other substrate. Organic solvents are

often required to remove or reduce residual adhesive. Pressure-sensitive adhesives arenot appropriate for use with permanently valuable archival materials.

Adhesives that are likely to be associated with records (either as part of their originalfabrication or applied later by their creator or donor) or used inhouse in an archivesinclude the following:

o Acrylic- Synthetic resin used as a fixative, consolidant, adhesive, and coating. Acryliccopolymer adhesives are strong, flexible, durable, and resistant to ultravioletdegradation and oxidation. Available in different formulations and applications,including solutions and as thermoplastic pressure-sensitive adhesives. Acrylicadhesives are recommended for fabricating enclosures and sealing taped polyesterfilm encapsulations. Acrylic dispersions are used in formulating "heat-set" tissue.

oAnimal glues- Proteinaceousadhesives produced from animal hides, skins, and bones,such as hide glue, parchment size, and gelatin (various grades used for sizing paperand photographic emulsions). Soluble in water. Traditionally used as an adhesive inbookbinding, though now replaced by polyvinyl acetates. Dries to a hard brittleconsistency; sometimes yellowish in appearance.

o Cellulose acetate- Producedby the reaction of cellulose with acetic acid in the presenceof a catalyst, usually sulphuric acid. Now considered unstable, cellulose acetate filmhas been used in laminating documents, and in solution as a consolidant for flakingmedia. Soluble in acetone. Cellulose acetates have also been used extensively as a


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photographic film base.o Cellulose nitrate-Formed by the reaction of cellulose with nitric and sulphuric acids.

The first synthetic plastic; used extensively as a photographic film base as well as aconsolidant and an adhesive. Also used as a coating, as with pyroxylin coated bookcloth. Unstable.

o Methyl cellulose-Semi-synthetic adhesive; one of many cellulose ethers. A relativelyweak adhesive, sometimes used for minor paper mends. Sets slowly; flexible;reversible with water. Also used as a poultice or sizing agent, and sometimes added topolyvinyl acetate or other adhesives to improve their working properties. Relativelylong shelf life; resistant to but not incapable of supporting mold growth.

o Starch paste- Mixtureof vegetable (generally wheat or rice) starch and water. Strongtacky adhesive used in paper and book conservation. Sets slowly; moderately flexibleif applied in a thin coat; reversible with water. Since pastes are susceptible to moldgrowth, fungicides are sometimes added. Dextrins are modified starches that havebeen widely used for stamps, envelopes, and similar uses where the adhesive ismoistened for application.

o Polyvinyl acetate (PVA)- Strong,flexible, synthetic polymer adhesive used especially inbookbinding and box making. Fast-drying white liquid that dries white to transparent,although certain formulations yellow with age. PVA can be diluted with water. Noteasily reversible; when dry, PVA will swell in water and some other solvents but will

not dissolve. Polyvinyl acetates can support mold growth; maximum shelf life ofabout one year. Should not be subjected to freezing temperatures, which hasimplications for the time of year PVA is shipped in or to cold climates. Not anappropriate adhesive for mending paper.

o Rubber-based-Originally,natural rubber dissolved in naphtha. Today, rubber-basedadhesives may be composed of natural or synthetic rubber and any of a wide varietyof plasticizers, resins, tackifiers, and other substances. They are relatively low-strengthand can cause permanent staining of paper. Rubber-based adhesives oxidize fairlyreadily, especially in the presence of light, and lose what little strength they have.Vulcanized rubber is chemically reacted with sulphur to increase its strength.Available in a number of forms, including rubber cement and pressure-sensitivesurgical, masking, and cellophane tapes. Should never be used with archivalmaterials; are especially damaging to photographs.

It can be difficult to learn about the composition and potential stability of adhesivessince most are commercial, proprietary products whose formulations are ever subject tochange. Therefore, it is important to proceed cautiously in specifying adhesives for dif-ferent applications and to contact the manufacturer for as much information as possibleregarding composition and aging properties. These data should be confirmed, however, byreviewing the preservation and conservation literature, and by contacting conservators,conservation scientists, and institutional research and testing laboratories.

This brief overview provides an introduction to materials that an archivist is likely toencounter with textual and graphic collections. Chapters 6 and 7 provide information on

the material nature of machine dependent records and resultant storage and handlingrequirements. The readings in the bibliography will provide further guidance in all of theseareas. However, reading books and articles must be combined with practical experiencewith the records themselves. It takes time to train one's eye and hand to discern subtlephysical differences between materials. Careful examination and handling of many, manyitems will help. Advice also should be sought from knowledgeable colleagues(conservators, preservation administrators, archivists, curators, and librarians). To adegree, self-education in this area must correct the deficiencies of most formal archival and


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library training programs. The goal is to approach and understand archival materials in away that combines intellectual interest in their content with a curiosity regarding theirphysical nature. A number of records appraisal decisions legitimately, and of necessity, re-late to considering archival materials from purely physical perspectives; an integratedrecognition of historical value and physical need is required. Further, the technicaldevelopment of record materials and the trades associated with them have a fascinatinghistory all their own. Archivists who are capable of understanding and appreciating therecords on this level as well will be better overall custodians of collections.


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1 The institutions holding these items shall remain anonymous, but the objects cited are actualexamples of non-traditional records!

2 During the hand papermaking process, suitable fibers are soaked in water, cooked incaustic soda and ash, and often fermented. The fibers are then macerated or beaten so that they

flatten out and small hairlike fibers called fibrils develop: The fibrils remain attached to the fibersand provide a greater surface for bonding during sheet formation. Originally, beating was doneby hand, as it still is today in some papermaking processes in various parts of the world.However, the water-driven stamping mill, invented in the twelfth century, speeded up the pro-cess and still produced a relatively long fibered pulp through the use of wooden beaters (orstampers) in a wooden tub. Once the fibers are macerated to a pulp, they are added to a vat ofwater to form a dilute slurry. The water swells the fibers, distributes them evenly in thesuspension, and promotes hydrogen bonding, which holds the dry fibers together. A paper moldis dipped into the vat vertically, lifted out horizontally, and shaken vigorously until an even layerof slurry rests on the porous screen of the mold (see Figures 3-3, 3-4). The slurry is retained by thesurround, or top half of the mold, called the deckle (see Figure 3-5). Excess water passes throughthe screen, which traps the fibers, and the remaining mat of fibers is laid (or couched) onto a

piece of wool felt. The paper sheet is formed by mechanical intertwining of the fibers, surfacetension between fibers, and chemical bonding of adjacent cellulose molecules (i.e., hydrogenbonding).

3 The first papermaking machine was invented by a Frenchman, Nicholas-Louis Robert, butwas named after Henry and Sealy Fourdrinier, London papermakers who provided the necessarycapital for the project. Bryan Donkin, an engineer, constructed the first operational machine,which was built after Robert's model; it was in use at the Frogmore Mill, Hertfordshire, in 1803.See Papermaking: Art and Craft (Washington, D.C.: Library of Congress, 1968), 55-56. In the UnitedStates, the first Fourdrinier machine was put into operation in 1827 in Saugerties, N.Y., whilepaper made by machine was first produced on a cylinder machine in 1817 near Wilmington, Del.,at the Gilpin Mill. The cylinder machine, patented in 1816 by Thomas Gilpin, involves a revolvingmold that is immersed in a vat of slurry; as the mold comes out of the vat, the fibers aretransferred to a couch roll. The paper is thus formed sheet by sheet, rather than in a continuous

roll as on the Fourdrinier machine. See Edwin Sutermeister, The Story of Paper

ritzenthaler 19-43

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