REVIEW OF EARLY STORAGE MEDIA DEGRADATION FACTORS, PRESERVATION TECHNIQUES AND TRENDS IN ETHIOPIA Bisrat Derebssa Dufera School of Electrical and Computer Engineering, Addis Ababa Institute of Technology, Addis Ababa University [email protected]

ABSTRACT

Since the invention of the Gramophone by played back in 1877 by recording human in 1877 society has used voice on a tinfoil wrapped around a different storage media to record and store cylinder. Since then recorded sound has sound as important aspect of human life. been an important aspect of human life. Continued preservation of these data for the Now music can be heard at home privately generation to come has been regarded as and it became possible to hear the same important goal of archivist and libraries. However, since analog storage media are not “performance” multiple times. With the permanent, these storage media are under risk invention of sound recording, educators of degradation and damage. As a result, several could bring sound recordings in classroom preservation techniques and guidelines have to aid the teaching-learning process. been prepared and applied to prolong the Another important aspect of recorded sound shelve life of these analog storage media. These is the preservation of oral culture. Folklore preservation techniques slow down the rate of and ethnographic collections “provide audio degradation; they do not stop or reverse it. As a windows into a range of cultures and result, the long-term solution is the digitization geographical areas. Perhaps no other sound of these recordings and copying them into the medium has conveyed to listeners so much newest format whenever there is a format history and culture, through music, diverse change. A review of degradation factors affecting storage media, preservation entertainment programming, daily news and techniques, digital preservation guidelines and public affairs, and interviews” [1]. current preservation techniques employed in A survey conducted by Heritage Ethiopia are presented in this paper. From the Preservation Inc. in partnership with the review, it has been observed that even though U.S. Institute of Museum and Library there are some institutions in Ethiopia that have Services of public institutions estimated that understood the problem of degradation and have taken actions to decrease its effect, some there are around 46 million individual institutions have not taken proper analog and recordings in these institutions of which digital preservation actions. As a result, the 44% of audio collections in their library statuses of their archives are not known and were in “unknown condition” [1]. The significant portions of their archives are Music Archive of the Ethnological Museum expected to be degraded. (Germany) houses 354-cylinder collections with approximately 16,800 recordings on Keywords: Early sound recordings, wax slightly over 30,000 cylinders and cylinder, disc, , approximately 3,500 magnetic tapes. Ethiopian broadcasting corporation, Institute of Ethiopian Studies The condition of the recordings is not well known [2]. The British Library estimates INTRODUCTION that of the 6.5 million sound recordings in Thomas Edison was the first that successfully recorded sound that could be

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Bisrat Derebssa its archive, 1 million of them are in risk of permanent media. Tasks that need to be disappearing [3]. taken by libraries and archivists are preservation, digitization, and restoration According to [4], the history of electronic [5]. media in Ethiopia starts with the first provisional radio station in 1933 by an Even though the long-term solution to these Italian Company. To the author‟s set of problems is digitizing the archives knowledge, the most important audio-visual and storing it in the latest format, most libraries in Ethiopia are the Ethiopian estimates agree that institutions have only a Broadcasting Corporation (EBC) audio- small window of time in which to complete video library, National Library of Ethiopia, high-quality digitization depending on and the Institute of Ethiopian Studies (IES) storage conditions, the storage media used library of Addis Ababa University. It is and other factors [6]. difficult literature on the status to obtain To get a clear picture of the problem facing of storage media in these Ethiopian audio- these storage media in Ethiopia, literature video Libraries. This may stem from lack of review and library survey were conducted. understanding of the risks facing storage The literature review and library survey media, lack of funding or lack of when presented together are hoped to shed experienced staff that can undertake the task light on the current Ethiopian audio-video of preservation. archive risks in a single setting. These audio recordings are stored in LITERATURE REVIEW different audio libraries and museums in different parts of the world. Several types of The literature review focuses on research storage media have been used according to that was conducted worldwide related to advances in technology and demands of the storage media degradation, analog market. A brief chronology of recorded preservation and digital preservation. Its formats commonly found in libraries, sound aim is to review degradation factors for archives and private collections is as each storage media and state of the art follows [1]. preservation techniques. It will be used to assess the progress done in Ethiopia.  1889: Wax Cylinder  1893: Flat disc Library Survey: In the library survey,  1902: Black-Wax Cylinder audio-video libraries in Ethiopia were  1940: Wire magnetic recorders surveyed to assess the status of the stored  1948: Magnetic tape media and preservation techniques  1948: Flat Discs of PVC employed. Oral interviews and library visits were conducted to assess the libraries. The  1958: Stereophonic LP discs results of these observations are then  1964: Compact compared to the degradation factors and  1982: Digital recorded compact state of the art preservation techniques that discs are obtained in the literature review.  1990: Recordable The literature review showed the significant The stored data in these storage media is risk of archived media. Even though the faced with two important and unavoidable library survey conducted is only done in problems: deterioration due to „natural two institutions, by analyzing its findings aging and improper storage environment‟, from the literature review it showed status and format obsolescence. Therefore, of the two possible extremes of audiovisual libraries and archivists are faced with the libraries on efforts made to preserve the task of copying these contents into a more data stored in the storage media.

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The paper has been organized in five moving the membrane. The vibrations are sections as follows. Section 1 briefly then amplified by the horn. discusses the problem and methodology to be used. Section 2 discusses the storage Cylinders may be divided into the following media that have been used in the past types and their degradation is also affected century from the point of view of their to a different degree. principle of operation and degradation Brown-Wax Cylinders factors. Section 3 discusses the different preservation techniques that have been used Brown wax is a "metallic soap," combined and applied for the different storage media. with natural waxes. This material is soft Section 4 discuss the findings of assessment enough to make a direct recording [10]. of EBC library and IES library on the status Playback of any wax cylinders at a of archived media in Ethiopia. Finally, temperature exceeding 25°C should be Section 5 concludes the paper by briefly absolutely avoided as wear may increase discussing the implication of each of the significantly with temperature [10]. In chapter and stating what needs to be done in addition, rapid temperature changes may the future and the current state of archived cause hairline cracks and total loss of a media in Ethiopia. record [10]. Because of their highly organic composition, they are unfortunately prone Storage Media Employed to fungus attack. Humidity and temperature Of the different media that have been used, significantly increase the rate of fungus the cylinder, flat disc, magnetic tape and infection. Often, they are found in an compact disc have the most of historical, unplayable condition because of this fungus cultural, entertainment and other data [1]. damage [10]. This is expected to be the case for Black-Wax Cylinders audiovisual media stored in Ethiopian libraries and archives. Of these, the compact Black-Wax cylinders are made from metal disc is the most recent and stable. A recent soaps (lead stearate) with carbon and study on accelerated aging test of compact additional hardening agents [10]. The main disc has reported the average life advantage of black-wax cylinders over expectancy of the compact disc under room brown-wax cylinder is that they can be mass temperature and controlled humidity to be produced by molding process [11]. Another 776 years [7]. Therefore, only the cylinder, advantage is that black-wax records can be flat disc and magnetic tape are considered played at higher speed than most brown- under significant risk and this review wax records. Therefore, they are louder and focuses only on these storage media. capable of better sound quality [10]. Black- wax cylinder is more brittle, and becomes Cylinder more so with age as compared to brown- Phonograph cylinders, classified as a wax cylinder. Similar to brown-wax mechanical carrier, are the earliest cylinder they are prone to microorganism commercial medium used for recording and damage. reproducing sound [8]. Sound, which is a Celluloid Cylinders function of air pressure variation was captured by a horn that moves a membrane Celluloid Cylinders were made from plaster which was connected to a cutting stylus [9]. core with celluloid plastic playback surface The stylus then carves these movements layer. Some of the advantages of celluloid into the surface of a rotating cylinder. records over wax records are: they are Playback worked in the opposite way – a rarely broken by mishandling, they are stylus was moved by the carved groove, durable and can be played repeatedly with

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Bisrat Derebssa less wear than wax records and they are provide the physical properties needed for resistant to fungus infection [9]. engraving the disk. The loss of castor oil causes shrinkage of the lacquer coating Camphor, a plasticizer in the celluloid, [12]. Because the coating is bonded to the evaporates over time causing the celluloid core and cannot shrink, the result is the tube to shrink in length and diameter. If the creation of internal stresses which result in celluloid cylinder is constrained by a core, cracking and peeling of the coating [12]. this can cause tears in the celluloid called Acetate discs are also affected by mold "end splits" [10]. Low temperature can be a [13]. high risk of breakage, as the celluloid will become significantly more brittle [9]. Shellac Discs Another problem is that core materials The shellac type disc is made of 70 percent (plaster and cardboard) can swell with or more of a mineral or cellulosic aggregate moisture and age. This may prevent the which is bound together and protected by cylinder from fitting on the phonograph resins and waxes as fillers [13]. The nature mandrel [9]. of the binder and fillers is important in Flat Discs determining the physical properties and A gramophone record, commonly known as response to aging of these discs, but these a disc, is a mechanical sound storage qualities are more dependent on the other medium in the form of a disc with an constituents than on the binder [12]. As a inscribed spiral groove. Its principle of result, it is quite difficult to determine the storage is by physically plotting the causes of shellac degradation. While the waveform of the audio signal on a disc [8]. shellac is fungus resistant, the organic The sound is collected by a horn that moves materials in the aggregates are susceptible a diaphragm, which vibrates the cutting to fungus attack. stylus. The resulting groove shape will be The curing process during shellac physical image of the movement of the manufacturing generates a condensation stylus. reaction between its organic compounds [5]. Discs may be divided into the following This reaction causes the shellac to shrink types and their degradation is also affected overtime, increasing its density and to a different degree. brittleness. This condensation continues at a much slower rate and this is the primary Acetate Disk degenerative force [5]. In storage these Instantaneous recordings were usually made discs suffer a slow, progressive on acetate discs until this medium was embrittlement of the shellac [5]. Due to this supplanted for this purpose by magnetic a fine powder is shed from the disc after tape. A lacquer coating, consisting of each playback. cellulose nitrate, carries the information. The substrate or support of the discs is Vinyl Discs usually made from metal or glass [8]. Vinyl discs are made of polyvinyl chloride Unfortunately, cellulose nitrate is an (PVC) and a small percentage of "fillers", unstable material. The most important stabilizer, pigment, anti-static substances, degradation reactions are thermal, photo- etc. [5]. The vinyl disc has been observed to oxidative, and hydrolytic decomposition be the most stable of the materials used in which result in chain scission or reduction the manufacture of discs. However, its life of molecular size. This results in is not indefinite. According to [14], no delamination and cracking of the lacquer systemic degradation of these materials is coating. Castor oil is used as a softener to expected in the near future. However, PVC

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Review of Early Storage Media Degradation Factors, Preservation Techniques… degrades chemically when exposed to Loss of lubricant (LoL): It is “the failure ultraviolet light or to heat [11]. Vinyl discs of a tape with sticky shed syndrome to be are prone to mechanical damage as they are restored to playability after a normal relatively soft compared with shellac discs. incubation or baking cycle” [6]. It has been recommended by Richard L. Hess [6] that Magnetic Tapes this terminology be properly referred as From its invention in Germany in 1935 and “Soft Binder Syndrome (SBS)” as the its rise to the primary medium for sound cause of the failure is not really a loss of recording worldwide, magnetic tape has lubricant. Playback is accompanied by earned a reputation as a reliable and high- squealing and the tape sticks to the fixed quality storage medium [15]. The recording surfaces that it may stop the playback. mechanism relies on a magnetic layer, binder, capable of „storing‟ the sound by Shedding and possible detachment is also retaining the magnetism impressed on them observed due to hydrolysis. It causes a by the recording head. This layer is weakening in the bond holding the binder to supported by the base film, which provides the base [16]. structural support [12]. Magnetic Tape Base The shelve life of magnetic tape is The base, the structural support of the tape, dependent on the formulation of magnetic must cope with stresses imposed by tape which is prone to degradation in playback and storage without becoming storage due to several factors; such as: type permanently deformed, or losing of magnetic tape, acidity, humidity and dimensional stability. The base film consists temperature of the storage environment. of, in historical sequence, acetate cellulose, These factors affect the binder and base PVC and polyester terephthalate, generally differently. called polyester, which has been in use since the late 1950s [17]. Magnetic Tape Binder Some of the factors that affect audio The following are some common quality, tapes aging properties, tape-to-head degradation effects that involve the contact and noise level are, binder chemical mechanics of the physical tape [6]. composition, uniformity and smoothness of Country laning: a tape deformation in which application [6]. The most common binder the tape does not lie straight but, rather, is resin used is polyester polyurethane. The wavy. This is usually the result of bad most common ferromagnetic particle used is slitting during manufacture or by a poor gamma ferric oxide (Fe302) [5]. According wind. to [6], two major binder coating failure modes are the following. Winding defects: “introduced by sloppy winding, the tape can have popped strands, Sticky shed syndrome (SSS): The binder have a portion of the pack slip, or be resin, which is made of ester, reacts with jammed against a flange” [18]. water from humidity to release carboxylic acid and alcohol. This results in the binder Edge frilling: “Tapes can frill or lose chips shedding a gummy and tacky material of oxide or base film at the edges of the which causes tape layers to stick together tape. This seems to be caused by [16]. This degradation is sometimes mechanical damage or possibly heat temporarily treated with incubation or damage during storage or playback” [18]. baking. Storage at high temperature and/or relative humidity levels may lead to fungus infection [17].

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Acetate: Acetate tape is generally robust and libraries to preserve the media can fall and it breaks cleanly rather than stretching into either of the following categories [14]. significantly prior to breaking when overstressed. These tapes rely heavily on Improvement of methods to identify and plasticizer additives for flexibility that treat endangered media, Improvement of evaporate and crystallize over time. This methods and material to decrease the rate of results in brittleness and drying. Acetate degradation, and Digital preservation tapes are prone to linear expansion in the Identification of Endangered Media presence of warm conditions or humidity. Due to the different properties of the binder There are different factors determining the and base, humidity and heat cause in tape life expectancy of a media. Some of the curling and edge fluttering [5]. High factors are storage media type, age, and temperature, high humidity levels, the storage history. It is reasonable to expect presence of iron oxide and the lack of any older recording to be in a more risk of ventilation lead to vinegar syndrome, which degradation and information loss than a occurs as acetate decomposes and forms recent one. Even though this assumption acetic acid [17]. Once it has started it can holds in most cases, other factors should only be slowed down, not reversed [17]. also be considered. For magnetic tape, age This is usually observed in tapes stored in by itself is not considered a major concern metallic containers. by archivists and preservation engineers [17]. Those that experience problems are Polyester: Polyester came into use in the usually plagued by issues unrelated to the early 1960s, and it quickly replaced acetate aging process by itself. Such issues are for magnetic tape backing [17]. Accelerated storage in metallic container in the presence aging tests have found polyester to be a of high temperature and humidity leading to stable material. This is due to the fact that it sticky-shed syndrome or improper handling undergoes hydrolysis degradation at a much before storage leading to winding defects, slower rate than the binder, polyester laning and others. Considering its longest polyurethane [19]. However, polyester- age, it is straightforward to deduce that the based tape has a high tensile strength that wax-cylinder is the most endangered media can cause it to stretch irreparably instead of of the three media formats [12]. The reason breaking cleanly. Such stretched tape can‟t for this can be fast degradation with age, be repaired as easily as acetate-backed tape instability of the material used and format which breaks cleanly [19]. obsolescence, Preservation Methods Considering the significant impact of Preservation, as defined by [5], is “all humidity and temperature on the actions taken to retard deterioration of, or to degradation of almost all storage medium, it prevent damage to, cultural property. is reasonable to expect a recording stored in Preservation involves controlling the an environment with reliable climate control environment and conditions of use, and may to be in a better condition than a recording include treatment to maintain a cultural that is stored in uncontrolled environment. property, as nearly as possible, in an As such, the presence of the humidity, unchanging state.” Since audiovisual temperature, magnetic fields, light and dust recordings are stored on storage media that in the storage history is important identifier cannot retain the data on them permanently, of a recording in risk [12]. digitization and continued copying of the digital files is necessary to ensure the long- time survival of the recordings [14]. The tasks that should be undertaken by archivist

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Methods to Decrease the Rate of read/write error reporting via error detection Degradation and correction coding. To decrease the rate of degradation, the Preserving digital audio recordings requires storage environment should be controlled to the active maintenance of the recordings. avoid degradation risks. Audio collections The Technical Committee of the should be stored in locations with the International Association of Sound and following conditions. Audiovisual Archives (IASA) has published Reliable climate control: Audio recordings two guides to audio preservation, “TC-04” should be kept at a low temperature and [20]. These guidelines, have become the humidity. However, magnetic tape should benchmark of digital audio preservation best practices. Even though there are still not be stored below 8°C, and no audio format should be stored at or below freezing issues that remain to be resolved and gaps temperatures [11]. For long-term storage it to be bridged within the audio preservation is recommended between 8–12°C and 25– community, there is agreement in principle 35% percent relative humidity on the following seven points [1]. Good ventilation: to filter out any dust and Digital storage medium is the preferred foreign matter that may accumulate. medium of preservation. Analog formats degrade over time – both physically and Sufficient floor loading capacity: to avoid sonically – even if they are stored under any physical damage to the medium due to ideal conditions of temperature and structural damage of the storage shelve. humidity. IN addition, analog formats cannot be copied without signal loss and Fire suppression systems Security some additional of noise. Recordings should also be protected against damage from light and magnetic fields. Digital audio files should be transparent, i.e., audibly indistinguishable from the Light: materials made of PVC are original. Linear pulse code modulation susceptible to degradation in the presence of (PCM) file format is the preferred encoding light especially UV light. Magnetic fields: method. It is the standard form of digital magnetic fields may disrupt magnetic audio audio in CDs, computers, digital telephony recordings. and other digital audio applications. Digital Audio Preservation Preservation transfers must be flat without Any medium used for sound recording will any equalization of the frequency range or deteriorate overtime. The process of use of restoration techniques. Flat digital preservation using analog video tape was files contain the most information that may through analog migration which is not an be used for restoration or post preservation exact copy. Digital preservation via high- reprocessing in the future, especially when quality digital audio files makes subsequent improved restoration approaches are copies produced by digital migrations bit- developed. for-bit identical with their predecessors. Digital audio preservation files must be This makes digital migration retain the recorded at high sampling and bit rates, and quality of the original . without any compression. Though there is However, there are some risks in digital no consensus on the exact sampling and bit preservation and migration: bits can be lost rates, they should be selected as the largest during storage or when files are migrated value the digitizer and storage space allows. [1]. These risks can be mitigated by good data-management practices such as Storage must be planned for the long term. Long-term preservation requires the

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Bisrat Derebssa migration of digital files over time and Ethiopian Broadcasting Corporation creation of digital-repositories. The last 130 years of audio archival experience shows us 1. Types of Storage Media that they get more precious they older they The audio-video media in EBC library are get. stored in magnetic tape, CD/DVD or . None of the data was stored in Rich metadata related to content, format, phonograph cylinder or flat disc formats, as and other attributes of the audio files must magnetic tape was the dominant storage accompany preservation files. Without media format when the corporation started systematic collection of structured operation. Of these media, only the information of the audio files it will be quite magnetic tape is in significant risk of difficult if not impossible to use them after degradation. some time where there may be change of personnel, organizational structure and 2. Storage History other factors. The storage age of the recordings ranges Professionalism is an essential component from few months to 70 years. The following of audio preservation. The continuous were observed about the audio-video training of staff to the latest techniques library. should be considered as a critical part of The recordings are well documented and digital preservation. catalogued. This is in line with one of the Ethiopian Context most important principles of archival – metadata management is a critical part of From the discussion thus far, it is clear that archival. all storage media that have been used worldwide are under significant risk of The storage media are stored in cardboard degradation and total loss of the data stored. boxes and plastic boxes. No recordings This is also true for the case of storage were stored in a metallic container that media used in Ethiopia. As such, the storage would increase the risk of degradation of history and preservation efforts that are magnetic tape. This is observed to have implemented in audio-video libraries in increased the shelf life of the magnetic tape Ethiopia, in combination with the – sticky shed syndrome has been avoided. degradation risks reviewed, can shed light on the status of the archived audiovisual Analog migration has been conducted history of the country. periodically. Even though analog migration is not a perfect migration, it has To understand the current condition of the considerably increased the shelf life of the storage media in Ethiopia, EBC library and magnetic tape storage media. In addition, IES library were selected for assessment. even though there is a significant age The libraries were visited to assess their difference on when they were recorded, the facility in terms of types of storage media, periodic analog migration has made them type of data, preservation efforts, much closer in storage age. assessment methods, and ongoing digitation efforts. A brief finding on the visit has been The audio/video library does not have air categorized into types of storage media conditioning. However, considering the average temperature and humidity in Addis employed, storage history and current 0 preservation efforts Ababa is 16.3 C and 60.7% respectively [21], the absence of air conditioning doesn‟t pose a significant degradation risk. For continued storage of these recordings, the

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Review of Early Storage Media Degradation Factors, Preservation Techniques… usage of climate control should be on the recordings that were too degraded to considered. be digitized. The audio-video library does not have air Video/TV filters. This poses degradation risk as the library is adjacent a main road. Fumes and Of the 35 thousand hours of video data in dust particles from vehicles may cause the audio-video library 11 thousand hours accelerated degradation as discussed in has been digitized and ingested into the section 2. For prolonged storage and digital archive. The remaining video data is preservation, the use of air filters should be in the process of digitization. considered. Similar to the audio/radio archival, the metadata management system is not Current Preservation Techniques Used comprehensive. The management of For continued usage, preservation and to aid metadata should be considered seriously as in easy access, EBC is digitizing all the it is a critical part of archival. media in its libraries. There are 35 thousand hours of analog video data and 82 years‟ worth of audio/radio broadcast data. The The video is stored in MXF format using radio and video digitation are carried out encoders to change different file formats, separately. The digitization efforts and their flv, avi, mp3, mp4 and others. Encoding and alignment with international guidelines on compression techniques that are used in digital preservation are discussed below. archiving should be carefully considered as Audio/Radio changes in technology may render the data unreadable. All the radio broadcast analog media data has been digitized and ingested to a central There are some video recordings that are digital archive along with important degraded and were difficult to read and metadata. digitize. It was not possible to obtain the exact figure of those that were degraded. Even though there is a metadata Restoration efforts should be considered on management system implemented, it is not these recordings. comprehensive. The management of metadata should be considered seriously as There are some recordings that couldn‟t be it is a critical part of archival. digitized because of format obsolescence. More efforts in obtaining spare parts or new The digital files are stored in WAV format professional equipment that can play these without compression. The WAV format recordings should be investigated. uses linear PCM which is in line with IASA guidelines. Institute of Ethiopian Studies (IES) Most of the analog media were in a good IES inherited its audio-video library from condition and as a result most of the digital Emperor Haile Selassie I, as such the some audio files have good quality. However, of the audio-video media are as old as there are very few recordings that could not almost 100 years old. be digitized due to significant degradation Types of Storage Media and format obsolescence. It was not possible to obtain the exact figure of those The audio-video media in IES library are that were degraded. In addition, there are stored in Phonograph Cylinder, Flat Disc some recordings which have low quality and Magnetic Tape (Open-reel, 35 mm due to degradation. Further investigation video film, High 8 film, VHS, Mini DV, and restoration efforts should be considered Unidentified magnetic tape media). The

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Bisrat Derebssa storage media in its archival are more Current Preservation Efforts susceptible to degradation as compared to The audio video media have not been EBC as they are older. Furthermore, digitized. The media are stored in their considering they have been in storage for as original storage media. Considering their far as a century ago, all the storage media age and uncontrolled environment they are are under significant risk of degradation. stored in, the audio-video media are in great Storage History risk of damage. It is anticipated that most of the recordings have some if not significant The following were observed about the amount of degradation. The quality and library where the audio-video media were extent of degradation of the media is not stored. known at this time. The recordings are not well documented IES is in pre-digitization. It is identifying and catalogued. It is not possible to the following factors that should be distinguish which of the recordings are in investigated before digitization. which format. As such, it is quite difficult Preservation efforts are being carried out and time taking to identify endangered currently. media which is the first step in any preservation effort. Conclusion and further work The storage media are not stored Over the past 140 years, humanity has systematically. The storage media are stored vast amounts of sound recording in scattered in different rooms and the storage different types of storage media. history in each of these rooms is not well Degradation factors on each of the storage documented. This makes determination of media have been reviewed. None of the quality of the recordings and identifying media are permanent and are under risk of degradation risk very difficult. degradation and data loss. Several preservation techniques and guidelines that No analog or digital migration have been increase the shelve life of these media have conducted. Furthermore, the recordings been reviewed. These preservation have not been copied to newer media techniques merely decrease the rate of periodically to retain their quality. degradation; they do not stop or reverse it. The main audio-video library has air As time goes by, the impact of these conditioning. However, not all rooms where degradation will be significant even if the the audio-video recordings are located have best preservation techniques are applied. air conditioning. For continued storage of The storage history and preservation these recordings, the usage climate should techniques used in Ethiopia have been be considered. reviewed. Even though the library survey None of the libraries have air filters. The conducted is not comprehensive, it shows main library is cleaned frequently and there status of the two possible extremes of was no noticeable dust on the shelves. audiovisual libraries on efforts made to However, the other rooms where the audio- preserve the data stored in the storage video recordings are located are not cleaned media. Considering the age of some of these frequently. As a result, the recordings in recordings and the lack of systematic these rooms are in significant risk of preservation techniques applied in some degradation and air filtering should be libraries, it is expected that there are considered in the future. significant number of recordings in libraries and archives that have been degraded.

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