In conservation, library and archival science, preservation is a set of preventive conservation activities aimed at prolonging the life of a record, book, or object while making as few changes as possible. Preservation activities vary widely and may include monitoring the condition of items, maintaining the temperature and humidity in collection storage areas, writing a plan in case of emergencies, digitizing items, writing relevant metadata, and increasing accessibility. Preservation, in this definition, is practiced in a library or an archive by a conservator, librarian, archivist, or other professional when they perceive a collection or record is in need of maintenance.
Preservation should be distinguished from interventive conservation and restoration, which refers to the treatment and repair of individual items to slow the process of decay, or restore them to a usable state. "Preventive conservation" is used interchangeably with "preservation".
Fundamentals
Standard functions of preservation programs Risk management in collections is the preventive care of a collection as a whole. Preservation can include general collections maintenance activities such as security, environmental monitoring, preservation surveys, and more specialized activities such as mass deacidification. Disaster preparedness (RT: Disaster Plan / Business Continuation / Disaster Recovery / Disaster Mitigation Plan) is the practice of arranging for the necessary resources and planning the best course of action to prevent or minimize damage to a collection in the event of a disaster of any level of magnitude, whether natural or human-made. Digital preservation is the maintenance of digitally stored information. Some means of digital preservation include refreshing, migration, replication and emulation. This should not be confused with digitization, which is a process of creating digital information which must then itself be preserved digitally. Reformatting is the practice of creating copies of an object in another type of data-storage device. Reformatting processes include microfilming and digitization.
Media-specific issues and treatments Books - Sizing and Leather Binding Ephemera and Realia Paper - Acid-free paper, Japanese tissue, Mummy paper, Paper splitting, and Print permanence Parchment - Parchment repair and Preservation of Illuminated Manuscripts Moving image - Film preservation and Video recording Sound recording - Preservation of magnetic audiotape Oral history preservation Language Preservation Visual material - Color photography § Preservation issues and Architectural reprography, a variety of technologies and media used to make multiple copies of original drawings or records created by architects, engineers, mapmakers and related professionals. Optical media preservation Ink
Digitization
A relatively new concept, digitization, has been hailed as a way to preserve historical items for future use. "Digitizing refers to the process of converting analog materials into digital form."
For manuscripts, digitization is achieved through scanning an item and saving it to a digital format. For example, the Google Book Search program has partnered with over forty libraries around the world to digitize books. The goal of this library partnership project is to "make it easier for people to find relevant books – specifically, books they wouldn't find any other way such as those that are out of print – while carefully respecting authors' and publishers' copyrights."
Although digitization seems to be a promising area for future preservation, there are also problems. The main problems are that digital space costs money, media and file formats may become obsolete, and backwards compatibility is not guaranteed.Rieger, 24–25 Higher-quality images take a longer time to scan, but are often more valuable for future use. Fragile items are often more difficult or more expensive to scan, which creates a selection problem for preservationists where they must decide if digital access in the future is worth potentially damaging the item during the scanning process. Other problems include scan quality, redundancy of digitized books among different libraries, and copyright law.Rieger, 14
However, many of these problems are being solved through educational initiatives. Educational programs are tailoring themselves to fit preservation needs and help new students understand preservation practices. Programs teaching graduate students about digital librarianship are especially important.
Digital Preservation is related to digitization. The main goal of digital preservation is to guarantee that people will have access to the digitally preserved materials long into the future.
Groups such as the Digital Preservation Network strive to ensure that "the complete scholarly record is preserved for future generations". The Library of Congress maintains a Sustainability of Digital Formats web site that educates institutions on various aspects of preservation: most notably, on approximately 200 digital format types and which are most likely to last into the future.
Practices When practicing preservation, one has several factors to consider in order to properly preserve a record: 1) the storage environment of the record, 2) the criteria to determine when preservation is necessary, 3) what the standard preservation practices are for that particular institution, 4) research and testing, and 5) if any vendor services will be needed for further preservation and potentially conservation.
Storage environment Environmental controls are necessary to facilitate the preservation of organic materials and are especially important to monitor in rare and special collections. Key environmental factors to watch include temperature, relative humidity, pests, pollutants, and light exposure.
In general, the lower the temperature is, the better it is for the collection. However, since books and other materials are often housed in areas with people, a compromise must be struck to accommodate human comfort. A reasonable temperature to accomplish both goals is 65–68˚F (18–20 °C). However, if possible, film and photography collections should be kept in a segregated area at 55 ˚F (13 °C).Lull, W.P. (1990). Conservation environment guidelines for libraries and archives; with the assistance of Paul N. Banks. Albany, NY: The University of the State of New York, The State Education Dept., The New York State Library, Division of Library Development.
Books and other materials take up and give off moisture making them sensitive to relative humidity. Very high humidity encourages mold growth and insect infestations. Low humidity causes materials to lose their flexibility. Fluctuations in relative humidity are more damaging than a constant humidity in the middle or low range. Generally, the relative humidity should be between 30 and 50% with as little variation as possible, however recommendations on specific levels to maintain vary depending on the type of material, i.e. paper-based, film, etc. A specialized dew point calculator for book preservation is available."Dew Point Calculator." Image Permanence Institute. Retrieved May 16, 2011 from http://www.dpcalc.org/ >
Pests, such as insects and vermin, eat and destroy paper and the adhesive that secures book bindings. Food and drink in libraries, archives, and museums can increase the attraction of pests. An Integrated Pest Management system is one way to control pests in libraries.
Particulate and gaseous pollutants, such as soot, ozone, sulfur dioxide, oxides of nitrogen, can cause dust, soiling, and irreversible molecular damage to materials. Pollutants are exceedingly small and not easily detectable or removable. A special filtration system in the building's HVAC is a helpful defense.
Exposure to light also has a significant effect on materials. It is not only the light visible to humans that can cause damage, but also ultraviolet light and infrared radiation. Measured in lux or the amount of lumens/m2, the generally accepted level of illumination with sensitive materials is limited to 50 lux per day. Materials receiving more lux than recommended can be placed in dark storage periodically to prolong the original appearance of the object.Thomson, G. The Museum Environment. 2nd ed. London: Butterworths, 1986
Recent concerns about the impact of climate change on the management of cultural heritage objects as well as the historic environment has prompted research efforts to investigate alternative climate control methods and strategies that include the implementation of alternative climate control systems to replace or supplement traditional high-energy consuming HVAC systems as well as the introduction of passive preservation techniques. Rather than maintaining a flat line, consistent 24/7 condition for a collection's environment, fluctuation can occur within acceptable limits to create a preservation environment while also thinking of energy efficiency and taking advantage of the outside environment.
Bound materials are sensitive to rapid temperature or humidity cycling due to differential expansion of the binding and pages, which may cause the binding to crack and/or the pages to warp. Changes in temperature and humidity should be done slowly so as to minimize the difference in expansion rates. However, an accelerated aging study on the effects of fluctuating temperature and humidity on paper color and strength showed no evidence that cycling of one temperature to another or one RH to another caused a different mechanism of decay.
The preferred method for storing manuscripts, archival records, and other paper documents is to place them in acid-free paper folders which are then placed in acid-free of low-lignin boxes for further protection. Similarly, books that are fragile, valuable, oddly shaped, or in need of protection can be stored in archival boxes and enclosures. Additionally, housing books can protect them from many of the contributing factors to book damage: pests, light, temperature changes, and water. Contamination can occur at the time of manufacture, especially with electronic materials. It must be stopped before it spreads, but it is usually irreversible.
Preservation criteria Making a proper decision is an important factor before starting preservation practices. Decision making for preservation should be made considering significance and value of materials. Significance is considered to have two major components: importance and quality. "Importance" relates to the collection's role as a record, and "quality" covers comprehensiveness, depth, uniqueness, authenticity and reputation of the collection. Moreover, analyzing the significance of materials can be used to uncover more about their meaning. Assessment of significance can also aid in documenting the provenance and context to argue the case for grant funding for the object and collection.
Forms of significance can be historically, culturally, socially, or spiritually significant. In the preservation context, libraries and archives make decisions in different ways. In libraries, decision-making likely targets existing holding materials, whereas in archives, decisions for preservation are often made when they acquire materials. Therefore, different criteria might be needed on different occasions. In general, for archive criteria, the points include:
the characteristics of a record (purpose, creator, etc.); the quality of the information in the record; the record in context (part of a series or not); potential use and possible limitations; and the cost against the benefits from its existence.
For archival criteria, the following are evidence of significance:
uniqueness, irreplaceability, high level of impact – over time or place, high level of influence, representation of a type, and comparative value (rarity, completeness, integrity relative to others of its kind).
Standards