Preservation and Conservation of Information
Preservation and Conservation of Information
PRESERVATION AND CONSERVATION OF INFORMATION
Information has been recorded throughout time in a wide variety of formats as human knowledge, ability, and skills developed. Cave paintings, papyrus scrolls, handwritten manuscripts, and visual or sound recordings in various languages and formats provide information to people and allow knowledge acquired by one generation to be passed to the following generation. Along with the oral tradition, images, sound, and text have assisted in the transfer of personal, educational, political, social, or cultural information. These materials comprise our collective memory and are valuable and necessary to a society or group of people.
It has been impossible to save all information created throughout the history of humankind. The beginning of the twenty-first century represents an era of unprecedented growth in the creation of recorded materials. Consequently, institutions that serve as custodians of cultural and historical information must make decisions regarding its collection, preservation, and conservation. Candidates for preservation encompass a variety of formats, such as paper, books, photographs, and sound recordings. The decision to save information is based on criteria that considers the uniqueness of the information, its intellectual content, its historical or cultural significance, and its value to future research and education. In addition, valuable items that are in danger of being destroyed are also candidates for preservation and conservation.
Items that comprise visual or artifactual information, rather than written information, may also be considered valuable. Materials such as books, archaeological artifacts, paintings, and other artistic works may not provide direct information in the traditional sense, but still have value due to the knowledge that can be derived from studying them. It is not uncommon that an object may have informational value in the traditional sense, through words, images, or sounds, and as an artifact. For example, a book generally contains information in the text, but it may also be an important artifact in that its structure and format provide information on the process of its creation.
Objects that show value for the information they contain or for the information they can provide are collected and preserved by institutions such as libraries, archives, and museums. These institutions make every effort to preserve objects in their original form. In addition, objects that are in bad physical condition, and therefore at great risk, become immediate candidates for preservation and conservation.
Conservation and Preservation
Preservation involves maintaining an object or information in a format that ensures the continued use and accessibility of the information provided. It includes developing criteria for selecting materials that have cultural or historical importance and assessing their preservation needs; halting the deterioration of materials by providing a stable environment and proper supplies and equipment for storage; developing and implementing policies for the safe use of materials; and providing the resources necessary to engage in an on-going preservation program committed to the continued existence of valued materials. Preservation also includes preparing for potential disasters such as floods, fires, tornadoes, and earthquakes. Conservation is a vital aspect of preservation. The goal of conservation is to stabilize and restore an object in its original form through various treatment methods. Professional conservators are trained to apply conservation treatment methods and make recommendations for long-term preservation of materials in suitable environments.
Preservation and conservation decisions are dependent on a variety of factors, the most important of which is the value of the information or intellectual content an object provides. Other factors that are considered include the uniqueness or rarity of an object; its connection with significant events, individuals, or places; its significance in relation to an institution and the mission of that institution; whether the information provided by the object is available elsewhere; and the consequences of the loss of the item or the information it contains. The current condition of an object, including its fragility and level of deterioration or wear that has occurred during its use serves as an important factor in preservation and conservation.
Conservators and preservation administrators often work with individuals who manage collections held in institutions such as libraries, museums, and archival repositories. Collections managers strive to meet the recommendations from professional conservators and preservation administrators and provide the ideal conditions for the media and artifacts housed in various institutions. Private collectors and individuals may seek similar advice and follow guidelines developed by professional conservators and preservation administrators to protect and preserve items they consider to be of value and to safeguard the information they contain.
While various materials and formats have special preservation needs, there are a few recommendations that are common to the long-term preservation of nearly every type of item. These recommendations deal with temperature, relative humidity, light, and air quality. High temperatures, high humidity, or large fluctuations or changes in temperature and humidity can damage most materials. High humidity encourages the growth of mold and mildew and affects the chemical makeup of items such as film, photographic prints, and audiotape or videotape. High temperatures often speed up the deterioration of materials. Although individual items have specific requirements for temperature and humidity, generally, a stable temperature of 70° Fahrenheit and a humidity range between 30 percent to 50 percent is recommended for proper storage. Light can fade ink and paper, and alter the appearance of photographs, paintings, and other types of artifacts. Air quality is also a consideration because dust, dirt, and other airborne pollutants can contribute to the deterioration of objects and artifacts.
Paper and Books
Since the development of paper-making techniques, paper has been used to record and transfer information, and thus has influenced the cultural and social history of the world. Paper assisted in spreading ideas and information in a form that became increasingly prevalent as people became literate. The availability of paper led to the creation of books, which enhanced the spread of ideas and information. Books are considered one of the greatest achievements of humankind. The information in books assisted in the education of people and the dissemination of knowledge and ideas. Initially, books were handwritten, rare, and available only to the wealthy. However, with the development of movable type, books became available to all people who could read or sought higher levels of education.
Throughout time, as the demand for books and the information they contain increased, efforts were made to find cheaper components with which to create books. In the mid-1800s, in an attempt to lower production costs, paper manufacturers turned to the use of wood pulp (from trees) in the paper-making process instead of linen and cotton rags. The acids in wood pulp, however, cause paper fibers to lose strength, become brittle, and slowly disintegrate. A familiar example of acidic paper is newsprint, the paper used to print newspapers, which is highly acidic.
An awareness of the loss of vast amounts of printed information due to the acid content of paper resulted in an increased use of alkaline or acid-free paper by book publishers. The use of paper that is acid-free serves as a long-term solution for preserving information.
Institutions that hold valuable artifacts and maintain collections of rare and unique books or collections of primary source materials in the form of manuscripts and written records strive to maintain the ideal environmental conditions for long-term preservation of these materials. In addition to environmental controls, papers containing valuable information should not be subjected to direct sunlight, ultraviolet rays, or fluorescent light, all of which can weaken paper and fade writing. Also, paper should not be handled while eating or drinking, as food and drink near books can attract insects and rodents that may damage the paper. As with all types of media that contain valuable information, paper should not be stored in attics, basements, or places where mold and mildew may develop or already be present. Books should be stored on metal shelves or sealed wooden shelves and should be shelved upright. Retrieve books with care and use a bookmark, and avoid writing in books or using tape that can cause damage.
Photographs record and store information regarding events, history, and people and provide through study a basis for the development of new information. Photographs are also an art form, comprising images created with a variety of techniques, such as the daguerreotype, tintype, and black-and-white and color prints. The process used to create each format is unique, however, the basis for producing photographs remains constant: exposing a mixture of chemicals on paper, film, or glass to light. The outcome of photography is both an image negative and a positive print image. Photographs and photographic paper are chemically complex structures and as such are more fragile and susceptible to adverse conditions than paper. Many steps can be taken to assist in the preservation of the information provided in photographs.
Photographs are susceptible to destruction caused by excessive exposure to light and physical and environmental fluctuations and hazards. They should be stored in an environment that does not have high temperature and high humidity or excessive fluctuations in temperature and humidity. An ideal temperature is 68° Fahrenheit with a relative humidity range from 35 percent to 40 percent.
Direct handling of photographs or touching the surface of a photograph should be avoided because oils and chemicals on human skin can permanently damage a photograph. Photographs should be protected from airborne pollutants, improper handling, as well as fingerprints, abrasions, dirt, pencil or pen marks, paper clips, and cracked surfaces. Photographs should be stored individually in paper that is acid-free or in plastic enclosures that are chemically inert. Paper enclosures protect images from light and avoid potential moisture buildup. Plastic or polypropylene or polyethylene enclosures allow an image to be seen without removing the image from the enclosure. Photographs are best stored in a dark closet on the first or second floor of a house, never in a basement or attic.
Slides consist of a transparent base, made from glass or film, that allows an image to be projected onto a screen. Both black-and-white and color slides are affected by the same environmental factors as photographs on paper. When slides are projected, the image is exposed to a great amount of both heat and light that adds to the deterioration of the slide. Slides are also affected by the acid content of cardboard sleeves or by the type of plastics used in the sleeves for the transparent image. Slides, as well as negatives, need to be treated with the same care and environmental considerations as print photographs.
Motion Picture Film, Audiotape, and Videotape
Films provide information in visual and audio form and are also considered to be artistic works. Motion picture film, both black-and-white and color, is composed of multiple layers that, due to their chemical components, can react to bad environmental and physical factors. Motion picture film is plastic that is made of nitrate, acetate, or polyester. Each of these types of film is coated with a chemical emulsion that holds the actual images.
Nitrate-based film, used prior to the 1950s on 35-mm format, is particularly unstable and can deteriorate rapidly in most storage conditions. It is highly flammable and the gasses emitted from the nitrate can invade and affect surrounding films. Because of these factors, nitrate film should be stored separately from all other materials in a collection. It should never be stored in an area that also serves as a living, working, or archival storage space for other materials. The deterioration of nitrate film can be slowed through stable cold storage at a temperature of less than 25° Fahrenheit. However, the best preservation option is to transfer nitrate film to modern, chemically inert polyester-based film.
Acetate has been used for 8-mm, 16-mm, and 70-mm film formats. Acetates are known as "safety" film because, unlike nitrate, they are not combustible. The plastic of the film can react with the atmosphere and create an acidic byproduct that gives off a vinegary odor, a form of deterioration known as "vinegar syndrome." This cannot be reversed and can spread to other films. Again, the best preservation method for nitrate-based film is transfer to polyester film.
Polyester is chemically inert and does not exhibit the same problems as nitrate-based and acetate-based films. All films are best stored horizontally, in chemically inert canisters, and in a controlled environment. High or fluctuating temperature and relative humidity can damage film by attracting mold, separating the emulsion layer of a film from its base, and accelerating chemical deterioration. Motion picture film should always be protected from light, dust, dirt, and fingerprints. All motion picture film is fragile and its base and emulsion layers can be easily damaged with improper handling or use in either a viewer or projector. For this reason, alternative copies may be produced for greater access to the information or content of the film.
Videotape, another common format for moving images and sound, may contain information that is considered highly popular, such as a copy of a popular movie, or may contain personal information, such as home videos. Videotape is an electromagnetic medium and as such is also highly affected by fluctuations in temperature and humidity, dust and dirt, use in poorly maintained playback machines, and magnetic fields. Videotape is not considered an appropriate medium for long-term preservation. Each time a videotape is played it loses some of the picture quality or signal. One way to ensure that the content of a videotape is not lost is to transfer it to polyester motion picture film and store it accordingly.
Audiotape, commonly found in cassette and reel-to-reel format, is subject to the same environmental and handling concerns as videotape. Analog reel-to-reel tape offers high-quality sound reproduction and is still considered the best preservation format for recordings on magnetic media. Audio-cassettes, which also consist of a magnetized plastic ribbon, are more accessible and less easily mishandled that reel-to-reel tapes, but their sound quality is significantly inferior. The temperature and humidity should not fluctuate and a temperature range from 60° to 70° Fahrenheit and a range of 20 percent to 30 percent relative humidity is best for storage. As with any audiovisual format, the equipment used to play tapes should be maintained in proper condition, kept free of dust and dirt, and the tape ribbon should be aligned properly on the reels to avoid distortion. It is also best to create copies of original tapes for access and use.
Preservation of moving images on film and videotape and of sound recordings on audiotape is important due to the unique information these formats contain. Yet their chemical and magnetic components, and their dependence on machinery that may become difficult to maintain or become obsolete, makes the preservation of the original format a challenge. For these reasons, audiovisual materials become candidates for transfer to a new format.
Sound recordings or phonograph records preserve information through music and recorded voice and allow such material to remain accessible over time. Recordings have been made on wax and metal cylinders, and on disks made of aluminum, glass, and vinyl. The sound signal is stored within the grooves of recording and is released through a stylus or needle when it is played. It is particularly important to protect these grooves from dirt, dust, and oil, which act as abrasives. In order to protect the grooves of a record and to decrease abrasions, phonographs should be housed in inner sleeves made of either an inert plastic, such as polyethylene, or acid-free paper. They should be stored vertically to avoid warping. Phonograph recordings should be stored in an environment that has a temperature of 68° Fahrenheit (plus or minus 5° Fahrenheit), and a relative humidity that ranges from 40 percent to 55 percent. In addition, a record should be handled by supporting the edge of the record and the paper cover in the center. Phonograph records can be cleaned with a soft lint-free cloth or brush.
Computer Disks, Compact Discs, and DVDs
Computer disks and compact discs have superseded other types of recording formats for information and data. For example, compact discs (also knows as CDs) have essentially replaced phonograph records for recording and distributing music. DVDs (digital video discs or digital versatile discs) have been introduced as a replacement for videotapes and as a way to store large amounts of information. Computer disks, compact discs, and DVDs store information in a digital format. Compact discs and DVDs are created using lasers that burn a sequence of binary code (composed of 0s and 1s) onto the bottom of a disc. Lasers both record and read information from the compact disc or the DVD without direct contact with the surface of the disc.
Computer disks and compact discs are composed of a variety of materials that affect the permanence of the information they hold. They can be affected by high fluctuations in temperature and humidity, as well as dirt and dust. These types of environmental hazards can cause the loss of part of the digital code. Both should be stored away from high temperatures or direct sunlight, and should be housed in dust-free containers. For compact discs, a soft, clean, dry cloth can be used to remove dirt, dust, or fingerprints from the surface of the compact disc. Water, solvents, or sprays are not necessary in order to clean a compact disc. Care must be taken to not scratch or damage the surface of a compact disc or the surface of a computer disk. Compact discs, DVDs, and computer disks should be kept away from magnetic field sources that may corrupt or destroy the information that they contain.
As with video and audio media, computer disks, compact discs, and DVDs are dependent on machines to read or access the information they contain. There is also information or computer data that is dependent on a specific type of software for retrieval and access. This means that it is essential to preserve the media as well as the computer equipment and software necessary to access the information. Computer equipment is susceptible to an adverse environment. High temperatures, dampness, and humidity, as well as dust and dirt, can damage computer equipment and destroy the information or data it contains.
Computer technology is constantly changing and many storage formats are no longer in use or available; for example, punch cards and 8-inch and 5-inch floppy disks. An option to ensure survival of the information stored on a computer disk, compact disc, or other type of media dependent on a computer is to convert or migrate the information to a new format every three to five years without the loss of intellectual content or the integrity of the information. Creation of digital media mandates a commitment to the maintenance of the format over time.
Facsimiles and Reformatting
The artifactual value of an object, or its value in its original form, may make it a candidate for conservation and preservation through the creation of a surrogate or facsimile. The use of surrogates prevents further damage to the original item, in whatever form, by allowing the surrogate to be used in place of the original. An object presenting information often has historic or intrinsic value and must be preserved in its original form. Other issues that contribute to the preservation of an artifact in its original form are its age and rarity. Sometimes, and for many reasons, objects or materials cannot be maintained in their original format and in such cases it may be acceptable to copy the content onto an alternative format that preserves the information but not the original format.
Reformatting original materials onto a new media ideally provides an accurate and quality reproduction of the original and allows the information it provides to be accessible over time. This also assures that deteriorating materials are no longer required for use, and those materials that are of significant value but also have the potential to experience further damage will be protected.
If a source of information, such as a book or a paper document, cannot be maintained in its original format, conversion to another medium is considered an option. Microform technology is an alternative format that preserves information and the intellectual content of materials. Micro-forms are considered to be one of the most stable preservation mediums for long-term access to information and materials that are not intrinsically tied to their original form. These types of materials most often consist of serials or periodicals, newspapers, and books that are valued for research and scholarship.
Microforms include microfilm, microfiche, and microprint, which are composed of microimages that are magnified through a lens provided in a microform reader. Due to the size of the images on microforms, a large amount of information can be preserved on microforms, which require a limited amount of storage space. Microfilm used for preservation is composed of a photosensitive emulsion made of silver halides. Microfilm made with silver halide and kept in stable, environmentally controlled storage can last for several hundred years. The proper temperature for the storage of microforms is 65° Fahrenheit, with a relative humidity of 35 percent (plus or minus 5 percent). Preservation of microforms also includes the creation of several copies. Silver halide 35-mm microfilm, usually the master copy or first generation of microfilm created, is considered the archival or permanent copy. A printing copy of microfilm is also produced and this copy is used to provide additional service copies that can be distributed for use and access to the information it contains. Service copies of microfilm are made of diazo or vesicular microfilm, which allows the materials to be used at a greater rate, while the master copy is preserved under proper environmental conditions. Microfilm is also considered a relatively inexpensive preservation option.
Almost every format and medium mentioned above, from books, sound recordings, videos, and microfilm, can be digitized. Digitization is recognized as a viable option for access to information and for the conversion of information into new formats. Transferring information from its original format to a binary code allows for greater manipulation of materials and the information they contain. Digitization provides greater access to information than any other type of format.
Reformatting and converting materials to a digital format assists in providing access to materials that are fragile, deteriorating, and still valuable based on the information or intellectual content they contain. Digitization provides a high-quality facsimile or surrogate of an original object or artifact. Transferring information to digital formats can assist in preservation because the original item, which is retained, is protected from additional handling that will further damage it. Digitization, however, does not constitute a long-term preservation method of information that is not preserved in its original form and it does not guarantee long-term access and authenticity of the information. It does not replace microfilming or other methods of preservation that can ensure long-term access and preservation. Digitization is preferred for improved access to materials rather than as a replacement of an original object or format that is best preserved in its original form.
Digital media, like magnetic media, requires machinery and software to read the binary code and present it to a user. Hardware and software components and human assistance is necessary to access digital information. Digital information must be migrated from outdated storage formats and software formats to current technology in order to ensure access to information considered to have long-term value.
Preservation assists in keeping information accessible and useful over time. Conservation treatments help to ensure the longevity of objects that have value for their content, so information can be learned from them as artifacts. Preservation and conservation efforts assist in research and scholarly activity but also affect daily life. Access to architectural records provides safety information for building and construction details that may prove useful during a natural disaster. State or municipal records that outline information on the storage of waste can ensure that housing developments are not placed in areas that once held waste materials. Photographs, maps, and other visual documents can help with the revitalization of neighborhoods and business districts. The records of organizations may help them plan community programs for the future.
The existence of information in its myriad forms, maintained or preserved over time, has benefits for all generations. It continues to provide the foundation for development of new information, knowledge, and skills. Societies and groups of people throughout history have sought to document their experience. It is from recorded information that we have learned about past cultures and peoples, how they lived, what they thought, what they placed value on, be it ideas or objects, and even what may have led to their demise. Information stored on paper, in books, through still and moving images, on sound recordings and electronic media, and in works of art, in original or surrogate form, help to define our culture and society, drives economic and political decisions, and should remain essential to our global heritage and cultures. Libraries, archives, local and state historical societies, conservation labs, museums, and related institutions serve as the custodians of these resources and as such make the effort to preserve information for generations to come.
DePew, John N. (1991). A Library, Media, and Archival Preservation Handbook. Santa Barbara, CA: ABC-CLIO.
Feather, John. (1991). Preservation and the Management of Library Collections. London: Library Association Publishing.
Greenfield, Jane. (1988). The Care of Fine Books. New York: Lyons and Burford.
Higginbotham, Barbra Buckner, ed. (1995). Advances in Preservation and Access, Vol. 2. Westport, CT: Meckler.
Lesk, Michael. (1992). Preservation of New Technology: A Report of the Technology Assessment Advisory Committee to the Commission on Preservation and Access. Washington, DC: Commission on Preservation and Access.
Ogden, Sherelyn, ed. (1992). Preservation of Library and Archival Materials. Andover, MA: Northeast Document Conservation Center.
Ritzenthaler, Mary Lynn. (1993). Preserving Archives and Manuscripts. Chicago: Society of American Archivists.
Smith, Abby. (1999). Why Digitize? Washington, DC:Commission on Preservation and Access.
Swartzburg, Susan G. (1995). Preserving Library Materials: A Manual. Metuchen, NJ: Scarecrow Press.
Task Force on Archiving of Digital Information Commission on Preservation and Access Research Libraries Group. (1996). Preserving Digital Information: Report of the Task Force on Archiving Digital Information. Washington, DC: Commission on Preservation and Access.
M. E. Ducey