Preservation
Preservation is a broad, overarching concept that encompasses all managerial, financial, and policy considerations necessary to prevent deterioration and ensure the longevity of library and archival materials and the information they contain. It is a generic term that includes all activities associated with maintaining resources and preserving their information content. The goal of preservation is to ensure that materials, regardless of their format, remain in an accessible form for as long as possible.
The need for preservation became a major concern in the mid-20th century, particularly after discovering that books published from the 19th century onwards were printed on acidic, wood-pulp-based paper, which was inherently self-destructive. This concern is now heightened by the fragility and technological dependency of digital materials.
1. Preservation of Print Materials:
- Causes of Deterioration: Print materials face threats from both internal and external factors.
- Internal Causes: The primary internal cause is the acidity of paper made from wood pulp, which contains chemically unstable lignin and acidic sizing agents like alum. This leads to hydrolysis and oxidation, making the paper brittle. The ink used from the 19th century, made of iron gall, can also form sulphuric acid and cause text to fade. Similarly, leather used for binding can become dry and break up over time.
- External Causes: These include environmental factors like light (especially ultraviolet and infrared radiation), which causes photochemical deterioration; fluctuations in temperature and relative humidity; air pollutants like sulphur dioxide that cause acid attacks; and biological agents such as mould, insects, and rodents. Human handling, negligence, theft, and vandalism are also significant external threats.
- Preservation Strategies: The main strategy is preventive preservation, which aims to create an ideal environment by controlling light, temperature, humidity, and pollutants. This also involves disaster management planning to protect against fire and water damage. When the physical artifact is too deteriorated, preservation focuses on saving the intellectual content by reformatting it into another medium like microfilm or a digital file.
2. Preservation of Non-Print (Analog) Materials:
- Causes of Deterioration: Non-print materials have their own unique vulnerabilities.
- Photographs and Films: These are subject to complex chemical decay. Cellulose nitrate films are highly flammable and emit destructive nitrous gases. Cellulose acetate films emit acetic acid vapour, which accelerates their decay.
- Magnetic Media (Audio/Video Tapes): These can be damaged by stray magnetic fields from equipment like speakers or microphones, which can erase the recorded information. Dust and dirt can prevent proper contact with replay heads and cause damage. Mechanical deformation during playback can also occur.
- Preservation Strategies: Strategies include storing these materials in controlled environments, away from magnetic fields. Originals of valuable items like photographs are often kept in passive storage at low temperatures, while surrogates (copies) are made available for active use. Careful handling by specialized personnel is also crucial.
3. Preservation of Electronic/Digital Materials:
- Causes of Deterioration: The greatest threat to digital materials is not physical decay but technical obsolescence.
- Digital data can be lost due to accidental erasure, viruses, and power failures.
- The primary challenge is the short life cycle of hardware, software, and storage media. Data can become inaccessible simply because the technology required to read it is no longer available, a problem exemplified by the BBC's 1986 Doomsday Book project.
- Digital materials are often "ephemeral" and require purposeful management to be retained.
- Preservation Strategies: Digital preservation requires active and continuous management. The UNESCO Charter on the Preservation of the Digital Heritage emphasizes international consensus on this issue. Key strategies include:
- Technology Preservation: Preserving the original software and hardware required to access the data.
- Digital Migration: Periodically re-encoding digital information into new, current formats before the old ones become obsolete.
- Emulation: Using software to mimic the original hardware and software environment to render the digital object.
- Digital repositories like DSpace are designed to preserve digital assets over the long term by managing the files (bitstreams) and their associated technical metadata.
Conservation
Conservation refers to the specific policies and practices involved in protecting library materials from damage and decay, including the specific treatments and techniques used by technical staff. While preservation is about overall management, conservation is about the direct, hands-on intervention to treat an artifact and extend its usable life.
Conservation activities for print materials include:
- Repair: Mending torn pages, patching damaged areas with strong, acid-free paper (like Japanese paper), and using archival-quality adhesives.
- Binding: Binding loose periodical issues or rebinding old, worn-out books in a durable "library style" to withstand heavy use.
- Refurbishing: A thorough, periodic cleaning of the collection and stack areas, during which each item is inspected for damage and identified for necessary treatment.
Archiving
Archiving is the process of selecting records for permanent or long-term preservation based on their enduring cultural, historical, or evidentiary value. While libraries primarily collect published materials, archives consist of records that are normally unpublished and unique, such as official files, manuscripts, and personal papers. An archive is also the institution or repository that houses these collections.
1. Archiving of Print and Non-Print Materials:
- Institutions like the National Archives of India act as repositories for the non-current records of the government, holding them in trust for administrators and scholars.
- Specialized archives exist for specific media, such as the National Film Archives of India, which safeguards the heritage of Indian cinema. Other examples include the Archives of Indian Labour.
- The fundamental mission is to preserve and make accessible these unique records of human endeavor.
2. Archiving of Electronic/Digital Materials:
- In the digital realm, archiving involves creating and maintaining repositories of digital content. Institutional Repositories (IRs) are a prominent example, serving as digital archives for the research output of an institution, including pre-prints, theses, and reports.
- Software such as DSpace and EPrints are used to build these repositories, which are designed to capture, store, distribute, and preserve digital assets.
- Archiving is a key function of many digital libraries, such as the Networked Digital Library of Theses and Dissertations (NDLTD), which archives electronic theses globally.
- Publishers and service providers also engage in digital archiving. For example, e-journal consortia often negotiate for archival rights to backfiles to ensure perpetual access to subscribed content. OCLC offers its members digitisation and archival services to protect and share their collections.
- Effective digital archiving requires robust preservation metadata (e.g., PREMIS) to support the long-term viability and authenticity of digital objects.