Preservation of magnetic audiotape comprises techniques for handling, cleaning and storage of magnetic audiotapes in an archival repository. Multiple types of magnetic media exist but are mainly in the form of open reels or enclosed cassettes. Although digitization of materials on fragile magnetic media in library and information science is a common practice, there remains a need for conserving the actual physical magnetic tape and playback equipment as artifacts.
The first magnetic tapes were manufactured by BASF in Germany in 1932. They were designed with iron carbonyl as the magnetic pigment mixed into the cellulose acetate carrier. Production soon moved to iron oxide coated onto cellulose acetate rolls cut into uniform strips wound onto plastic or metal hubs. Recordists began recording sound on magnetic media in the twenties in the form of magnetic wire. After World War II, the advantages of tape in terms of sturdiness and the ability to edit by cutting and splicing made tape preferable to wire as the magnetic medium of choice. Tape consists of a coating of a magnetic pigment, typically iron oxide (Fe2O3), on a long strip of polyester (polyethelyne terephthalate) base film. This base film has been used since the mid-sixties as a replacement for acetate bases film that was prone to chemical instability.
A new problem with chemical stability became notable in the mid-seventies when two significant tape manufacturers changed their dispersion formulations by introducing a polyurethane binder that, in time, turned hygroscopic and broke down as it absorbed water molecules into the long hydrocarbon molecular chains. The tape coatings became sticky and shed oxide onto all tape recorder parts in their path, including heads, guides, rollers, and capstans. This is commonly called sticky-shed syndrome. Although the problem was confined to two of the four major tape manufacturers (neither BASF nor 3M studio tapes suffer from the problem because neither manufacturer used the hygroscopic binder), the reputation of all magnetic tapes has been tainted by the defect.
Information can be recovered from the "sticky-shed" tapes by heating them at a very low temperature in order drive the water out of the binders. [1] The baking method is a one-time solution to the problem because the binder remains unstable. Tapes that do not show the breakdown syndrome do not need any special treatment.
It is advised that open reels are handled by the center hub area or by the outer edges of the reel flanges, if necessary, and that the actual tape is not touched. If the outer flanges must be used, do not squeeze the edges of the reel flanges together, as it will damage the edges of the tape. If possible, handle by the center hub only. [2] Similarly, it is recommended that cassettes be handled by the existing outer plastic case and that fingers not be placed anywhere inside the cassette mechanism. [3]
Magnetic tape must be kept clean in order to prevent scratching and deterioration. Dust on the surface of tape will cause friction between the tape and the tape heads on the playback equipment, which will scratch the oxide layer. The website for sound preservation hosted by the National Library of Canada classifies dirt in two classes: Foreign matter (fingerprints, dust) and alteration of the original state (chemical reactions caused due to grime and dirt deposited on the tape surface). [2] In any event, the tapes must be properly cleaned.
Recommended methods for removing dust on tapes include using a small vacuum with a hose or wipe with 3M Tape Cleaning Fabric. Care must be used when using a vacuum if a hose attachment is available. If the motor of the vacuum is powerful enough, it can demagnetize the tape and the recording will be compromised. Many of the professional companies for tape restoration recommend professional help for proper care. They are generally correct to recommend this, as it is a delicate process that requires training if one plans to undertake serious chemical or physical repair. Vidipax, a professional tape restoration company, recommends using Pellon fabric or cloth as the safest and most efficient way to clean tapes. They warn against using solvents at all costs unless the tapes have already been submerged in water or another solvent (in the case of a flood). They also remind tape-owners or collections managers that baking tapes to reverse hydrolysis is rarely a permanent fix and permanently alters the make-up of the tape. [4]
As is the case with any collection, proper storage is extremely important. The general environment, including temperature and relative humidity is key. The proper levels vary depending on how long the materials need to be stored. The Library of Congress [3] recommends that any tapes needing preservation for a minimum of 10 years should be stored between 65–70 °F (18–21 °C) at 45-50% relative humidity (RH). Large fluctuations in either of these factors should be avoided at all costs. If the tapes need permanent preservation, they should be stored at 46–50 °F (8–10 °C) at 20-30% relative humidity. In the case of magnetic tapes, contrary to traditional preservation storage rules for books and photographic film, colder is certainly not better. If the collections are stored below 46 °F (8 °C), the tape lubricant can separate from the base, ruining the recording. The most important thing is to keep conditions consistent once desirable conditions are achieved.
The National Library of Canada recommends that one and a half rounds of a previously unused tape should be cut off, so as to remove any adhesive at the end, which could later be transferred to the tape or machinery. They also recommend not storing any paper labels in the box with reel-to-reel tapes to prevent chemical transfer from the paper and/or printing processes used on the paper to the tape. [2]
The Library of Congress recommends that tapes with water repellent plastic containers be stored vertically on edge, not flat, and that reel-to-reel boxes need not be separated, but should be stored vertically with bookends, so as not to fall. Also, it is always important to remember that these collections will be very heavy and should be shelved on strong, non-acidic shelving.
Tapes should only be rewound just before the next play. When rewinding, if possible, use a slower archival wind technique. Although super-speed rewinders may seem convenient, they will warp and damage tapes over time. Professional media librarians at the National Library of Canada suggest that the best way to achieve an archival wind for reel-to-reel tapes is to remove the heads on the player and play backwards at normal play speed. However, the tape tension may need to be adjusted after removing the heads.
Sometimes, a tape may be so fragile that the only long-term method for preservation is to transfer the media to a digital format. However, all of the above precautions still must be taken with collections in order to achieve a proper transfer. The materials must be in good enough condition to play in order to be digitized; therefore, one should not count on digitization as a safety net.
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic tape could with relative ease record and playback audio, visual, and binary computer data.
An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present-day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal. Tape-recording devices include the reel-to-reel tape deck and the cassette deck, which uses a cassette for storage.
Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the supply reel containing the tape is placed on a spindle or hub. The end of the tape is manually pulled from the reel, threaded through mechanical guides and over a tape head assembly, and attached by friction to the hub of the second, initially empty takeup reel. Reel-to-reel systems use tape that is 1⁄4, 1⁄2, 1, or 2 inches wide, which normally moves at 3+3⁄4, 7+1⁄2, 15 or 30 inches per second. Domestic consumer machines almost always used 1⁄4 inch (6.35 mm) or narrower tape and many offered slower speeds such as 1+7⁄8 inches per second (4.762 cm/s). All standard tape speeds are derived as a binary submultiple of 30 inches per second.
Preservation of documents, pictures, recordings, digital content, etc., is a major aspect of archival science. It is also an important consideration for people who are creating time capsules, family history, historical documents, scrapbooks and family trees. Common storage media are not permanent, and there are few reliable methods of preserving documents and pictures for the future.
The conservation and restoration of photographs is the study of the physical care and treatment of photographic materials. It covers both efforts undertaken by photograph conservators, librarians, archivists, and museum curators who manage photograph collections at a variety of cultural heritage institutions, as well as steps taken to preserve collections of personal and family photographs. It is an umbrella term that includes both preventative preservation activities such as environmental control and conservation techniques that involve treating individual items. Both preservation and conservation require an in-depth understanding of how photographs are made, and the causes and prevention of deterioration. Conservator-restorers use this knowledge to treat photographic materials, stabilizing them from further deterioration, and sometimes restoring them for aesthetic purposes.
A film base is a transparent substrate which acts as a support medium for the photosensitive emulsion that lies atop it. Despite the numerous layers and coatings associated with the emulsion layer, the base generally accounts for the vast majority of the thickness of any given film stock. Since the late 19th century, there have been three major types of film base in use: nitrate, acetate, and polyester.
The conservation and restoration of vinyl discs refers to the preventive measures taken to defend against damage and slow degradation, and to maintain fidelity of singles, 12" singles, EP’s, and LP’s in 45 or 33⅓ rpm 10" disc recordings.
Oral history preservation is the field that deals with the care and upkeep of oral history materials, whatever format they may be in. Oral history is a method of historical documentation, using interviews with living survivors of the time being investigated. Oral history often touches on topics scarcely touched on by written documents, and by doing so, fills in the gaps of records that make up early historical documents.
The conservation and restoration of parchment constitutes the care and treatment of parchment materials which have cultural and historical significance. Typically undertaken by professional book and document conservators, this process can include preventive measures which protect against future deterioration as well as specific treatments to alleviate changes already caused by agents of deterioration.
Cellulose acetate film, or safety film, is used in photography as a base material for photographic emulsions. It was introduced in the early 20th century by film manufacturers and intended as a safe film base replacement for unstable and highly flammable nitrate film.
The conservation and restoration of textiles refers to the processes by which textiles are cared for and maintained to be preserved from future damage. The field falls under the category of art conservation, heritage conservation as well as library preservation, depending on the type of collection. The concept of textile preservation applies to a wide range of artifacts, including tapestries, carpets, quilts, clothing, flags and curtains, as well as objects which "contain" textiles, such as upholstered furniture, dolls, and accessories such as fans, parasols, gloves and hats or bonnets. Many of these artifacts require specialized care, often by a professional conservator.
Sticky-shed syndrome is a condition created by the deterioration of the binders in a magnetic tape, which hold the ferric oxide magnetizable coating to its plastic carrier, or which hold the thinner back-coating on the outside of the tape. This deterioration renders the tape unusable. Some kinds of binder are known to break down over time, due to the absorption of moisture (hydrolysis).
Collection maintenance is an area of collections management that consists of the day-to-day hands on care of collections and cultural heritage. The primary goal of collections maintenance or preventive conservation is to prevent further decay of cultural heritage by ensuring proper storage and upkeep including performing regular housekeeping of the spaces and objects and monitoring and controlling storage and gallery environments. Collections maintenance is part of the risk management field of collections management. The professionals most involved with collections maintenance include collection managers, registrars, and archivists, depending on the size and scope of the institution. Collections maintenance takes place in two primary areas of the museum: storage areas and display areas.
The conservation and restoration of books, manuscripts, documents, and ephemera is an activity dedicated to extending the life of items of historical and personal value made primarily from paper, parchment, and leather. When applied to cultural heritage, conservation activities are generally undertaken by a conservator. The primary goal of conservation is to extend the lifespan of the object as well as maintaining its integrity by keeping all additions reversible. Conservation of books and paper involves techniques of bookbinding, restoration, paper chemistry, and other material technologies including preservation and archival techniques.
Conservation and restoration of objects made from plastics is work dedicated to the conservation of objects of historical and personal value made from plastics. When applied to cultural heritage, this activity is generally undertaken by a conservator-restorer.
The conservation and restoration of time-based media art is the practice of preserving time-based works of art. Preserving time-based media is a complex undertaking within the field of conservation that requires an understanding of both physical and digital conservation methods. It is the job of the conservator to evaluate possible changes made to the artwork over time. These changes could include short, medium, and long-term effects caused by the environment, exhibition-design, technicians, preferences, or technological development. The approach to each work is determined through various conservation and preservation strategies, continuous education and training, and resources available from institutions and organization across the globe.
Conservation-restoration of bone, horn, and antler objects involves the processes by which the deterioration of objects either containing or made from bone, horn, and antler is contained and prevented. Their use has been documented throughout history in many societal groups as these materials are durable, plentiful, versatile, and naturally occurring/replenishing.
The conservation and restoration of paintings is carried out by professional painting conservators. Paintings cover a wide range of various mediums, materials, and their supports. Painting types include fine art to decorative and functional objects spanning from acrylics, frescoes, and oil paint on various surfaces, egg tempera on panels and canvas, lacquer painting, water color and more. Knowing the materials of any given painting and its support allows for the proper restoration and conservation practices. All components of a painting will react to its environment differently, and impact the artwork as a whole. These material components along with collections care will determine the longevity of a painting. The first steps to conservation and restoration is preventive conservation followed by active restoration with the artist's intent in mind.
The conservation and restoration of film is the physical care and treatment of film-based materials. These include photographic film and motion picture film stock.
The conservation and restoration of photographic plates is caring for and maintaining photographic plates to preserve their materials and content. It covers the necessary measures that can be taken by conservators, curators, collection managers, and other professionals to conserve the material unique to photographic plate processes. This practice includes understanding the composition and agents of deterioration of photographic plates, as well as the preventive conservation and interventive conservation measures that can be taken to increase their longevity.