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Preservation of magnetic audiotape comprises techniques for handling, cleaning and storage of magnetic audiotapes in an archival repository. Multiple types of
magnetic media Magnetic storage or magnetic recording is the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetisation in a magnetizable material to store data and is a form of non-volatile memory. The information is ac ...
exist but are mainly in the form of open reels or enclosed cassettes. Although
digitization DigitizationTech Target. (2011, April). Definition: digitization. ''WhatIs.com''. Retrieved December 15, 2021, from https://whatis.techtarget.com/definition/digitization is the process of converting information into a digital (i.e. computer-r ...
of materials on fragile magnetic media in
library and information science Library and information science(s) or studies (LIS) is an interdisciplinary field of study that deals generally with organization, access, collection, and protection/regulation of information, whether in physical (e.g. art, legal proceedings, et ...
is a common practice, there remains a need for conserving the actual physical magnetic tape and playback equipment as artifacts.


Structure of magnetic tape

The first magnetic tapes were manufactured by
BASF BASF SE () is a German multinational chemical company and the largest chemical producer in the world. Its headquarters is located in Ludwigshafen, Germany. The BASF Group comprises subsidiaries and joint ventures in more than 80 countries ...
in
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...
in 1932. They were designed with iron carbonyl as the magnetic pigment mixed into the
cellulose acetate In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and ...
carrier. Production soon moved to
iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of wh ...
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 Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is co ...
. After
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, 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 Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of wh ...
( Fe2O3), on a long strip of
polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natura ...
(polyethelyne terephthalate) base film. This base film has been used since the mid-sixties as a replacement for
acetate An acetate is a salt formed by the combination of acetic acid with a base (e.g. alkaline, earthy, metallic, nonmetallic or radical base). "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called ...
bases film that was prone to chemical instability.


Sticky-shed syndrome

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 Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...
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 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 de ...
. 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 "stick-shed" tapes by heating them at a very low temperature in order drive the water out of the binders. 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.


Handling

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.(1997, October 29). Preservation of Recorded Sound Materials. Retrieved April 9, 2007, from Music Division: National Library of Canada Web site

/ref> Similarly, it is recommended that Compact Cassette, cassettes be handled by the existing outer plastic case and that fingers not be placed anywhere inside the cassette mechanism.Library of Congress, (2006, December 11). Cylinder, Disc, and Tape care in a nutshell. Retrieved April 9, 2007, from The Library of Congress: Preservation Web site

/ref>


Cleaning

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 An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
layer. The website for sound preservation hosted by the
National Library of Canada Library and Archives Canada (LAC; french: Bibliothèque et Archives Canada) is the federal institution, tasked with acquiring, preserving, and providing accessibility to the documentary heritage of Canada. The national archive and library is ...
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). 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.Vidipax, (2007). Magnetic Tape Restoration. Retrieved August 2, 2008, from the Vidipax Web site:


Storage

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 recommends that any tapes needing
preservation Preservation may refer to: Heritage and conservation * Preservation (library and archival science), activities aimed at prolonging the life of a record while making as few changes as possible * ''Preservation'' (magazine), published by the Nat ...
for a minimum of 10 years should be stored between at 45-50%
relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...
(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 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 , the tape
lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
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 Library and Archives Canada (LAC; french: Bibliothèque et Archives Canada) is the federal institution, tasked with acquiring, preserving, and providing accessibility to the documentary heritage of Canada. The national archive and library is ...
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. The
Library of Congress The Library of Congress (LOC) is the research library that officially serves the United States Congress and is the ''de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The libra ...
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.


Digitization

Sometimes, a tape may be so fragile that the only long-term method for preservation is to transfer the media to a
digital format Digital data, in information theory and information systems, is information represented as a string of discrete symbols each of which can take on one of only a finite number of values from some alphabet, such as letters or digits. An example is ...
. 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.


See also

*
Magnetic tape sound recording 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- ...
*
Sticky-shed syndrome 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 de ...


References

Additional Sources: *Schüller, D. and Häfner, A. 2014
''Handling and Storage of Audio and Video Carriers''
International Association of Sound and Audiovisual Archives. *Stauderman, Sarah
''Pictorial Guide to Sound Recording Media''
Preservation: Sound Savings, preserving Audio Collections. Association of Research Libraries. *National Recording Preservation Board, Capturing Analog Sound for Digital Preservation: Report of a Roundtable Discussion of Best Practices for Transferring Analog Discs and Tapes. Washington DC: Library of Congress, 2006 *Hess, Richard L.. "The Jack Mullin/Bill Palmer Tape Restoration Project." Journal of Audio Engineering 49 (2001): 671-674 *Hess, Richard L.. "Tape Degradation Factors and Challenges in Predicting Tape Life." ARSC Journal 39 (2008): p. 240-274. *Engel, Fredrich, and Peter Hammer. A Selected History of Magnetic Recording. New York: 2006. *Cohen, Elizabeth. "Preservation of Audio." Folk Heritage Collections in Crisis (2001): 20-31. {{DEFAULTSORT:Magnetic audiotape preservation Audio storage Audiotape preservation Sound recording Tape recording