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Within the group of documents commonly labelled audiovisual (photographic
still and moving images, audio and video recordings) are sound
recordings on cylinders and discs. The common factor with this
group of documents is the method of recording the information.
This is by means of a groove cut into the surface by a cutting
stylus and which is modulated by the sounds, either directly in
the case of acoustic recordings or by electronic amplifiers.
There are no official standards for the preservation of these
materials but there are, however, a number of standard reference
publications available. These are listed in the Bibliography that
follows. In addition, the Proceedings of the series of Technical
Symposia organised by the international archive federations (FIAF,
FIAT, IASA and ICA) on the preservation of sounds and moving images
contain many papers of interest.
Phonograph Cylinders
Cylinders, originally developed for use as dictating devices, have been used since around 1889 for original recordings in the academic world and later also as mass produced recordings for the entertainment industry in competition with early gramophone (shellac) discs. While industrial production ceased in the late twenties, they continued to be used for field recording until the
1950s (!). Most cylinders are made of wax; some of the mass replicated
cylinders are made from celluloid. There are about 300,000 cylinders
in the custody of recorded sound collections worldwide.
They are extremely brittle and fragile and if they have been stored
under conditions which are too humid, they suffer from mould.
Fortunately, most of these holdings have already been transferred
onto modern media and thus their contents, which are frequently
of unique historical value, are already safeguarded .
Shellac Discs
Coarse groove gramophone discs, commonly called shellacs or 78s,
were the main mass produced audio format of the first half of
our century. It is estimated that the worldwide stocks of
this format amount to 10 million discs. They were produced from
1898 until the midfifties. The discs consist of various
mineral substances bound together by organic substances like shellac
or similar binding materials. Although breakable if dropped, these
gramophone records are fairly stable and there are no reports
of a systemic instability problem.
Instantaneous Discs
Prior to the introduction of magnetic tape, which occurred in
the late 1940s and early 1950s, the "instantaneous discs"
- so called because they can be played immediately after recording
the sounds without the need for the lengthy processes required
for mass produced discs - were the only medium for audio recordings
that could be played back immediately. The total number in existence
amounts to about three million. Practically all of these discs
are irreplaceable originals, many of them of great cultural, historical
and scholarly importance.
Unfortunately, the largest group of these instantaneous discs,
the "acetate discs", are at the greatest risk. These
discs are laminates consisting of a core plate, usually of aluminium
but plates of glass, steel and card are also known, with a lacquer
coating of nitrate or acetate cellulose which is soft enough to
be cut by a recording machine, but hard enough to withstand several
replays. With age, the coating shrinks and becomes brittle by
a hydrolytic process: the stresses between the shrinking lacquer
and the stable core increase until, suddenly, the lacquer breaks
apart, and flakes off. By this means a considerable portion of
the holdings worldwide have already been lost. Even if programmes
to transfer the sounds were hastily established, further losses
of irreplaceable information cannot be prevented. Every day,
apparently intact records are being affected by this phenomenon.
Microgroove Discs
From the late 1940s onward microgroove discs (vinyl or LP records)
replaced shellac discs and only relatively recently (since about
1990) has this format been replaced by the compact disc (CD).
The total number of microgroove discs in sound archives worldwide
is estimated to be more than 30 million. They are made mainly
of polyvinyl chloride. No systematic stability problems on a
great scale have arisen so far, but their stability in the long
term, thinking in centuries, is unknown.
The Stability of Mechanical Carriers
The main factors related to instability of mechanical carriers
and retrievability of information can be summarized as:
Humidity, as with all other data carriers, is a most dangerous
factor. While shellac and vinyl discs are less prone to hydrolytic
instability, most kinds of instantaneous discs are extremely endangered
by hydrolysis. Additionally, all mechanical carriers may be affected
by fungus growth which occurs at humidity levels above 65% RH.
Elevated temperatures beyond 60°C
are dangerous, especially for vinyl discs and wax cylinders. Otherwise,
as with other carriers, the temperature determines the speed of
chemical reactions like hydrolysis and should, therefore, be kept
reasonably low and, most importantly, stable to avoid unnecessary
dimensional changes.
Mechanical integrity is of the greatest importance for
mechanical carriers. It is imperative that scratches and other
deformation caused by careless operation of replay equipment are
avoided. The groove that carries the recorded information must
be kept in an undistorted condition. Only specialist personnel
should, therefore, be allowed to handle and replay mechanical
carriers.
While shellac discs are very fragile, instantaneous and vinyl
discs are more likely to be bent by improper storage. Generally,
all mechanical discs should be shelved vertically. The only exceptions
are some soft variants of instantaneous discs.
Dust and dirt of all kind will deviate the pick-up stylus
from its proper path causing audible cracks and clicks. Fingerprints
are an ideal adhesive for foreign matter. A dust-free environment
and cleanliness is, therefore, essential.
Obsolescence of hardware is not yet a major issue for mechanical
carriers. Replay equipment for microgroove and 78rpm discs is
still available and several sound archives have constructed cylinder
replay machines which offer excellent performance for cylinders
of all formats. With the exception of instantaneous discs and
cylinders, mechanical carriers are not generally at risk. Because
the discs wear when played, migration to a modern digital format
will be necessary for items in frequent demand.
Because of the extreme risk to the future survival of instantaneous
discs, all existing holdings must be transferred with highest
priority.
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Operation areas (studios) should have the same climatic conditions
as access storage areas.
It is of utmost importance to control both temperature and
humidity simultaneously. Archivists are explicitly warned to not
to cool the storage environment without dehumidification because
such action will normally lead to an unacceptable rise of relative
humidity and may encourage the growth of moulds and fungi.
Standards and Recommended Practices
IASA TC03 | The Safeguarding of the Audio Heritage: Ethics, Principles and Preservation Strategy. 1997 |
Reference Literature
Burt, LS
Chemical Technology in the Edison Recording Industry.
In: Journal of the Audio Engineering
Society 1011/1977
Calas, MarieFrance, et Fontaine, JeanMarc
La conservation des documents sonores.
CNRSEditions, Paras 1996
Khanna, SK
Vinyl Compound for the Phonographic Industry.
In: Journal of the Audio Engineering
Society 1011/1977
Pickett, AG and Lemcoe, MM
Preservation and Storage of Sound Recordings.
Washington 1959. Reprint by ARSC, 1991
Schüller, Dietrich
Behandlung, Lagerung und Konservierung von Audio und Videoträgern.
In: Das Audiovisuelle Archiv, Das Audiovisuelle Archiv 31/32, 1992
(1993)
Schüller, Dietrich
Preservation of Audio and Video Materials in Tropical Countries.
In: IASA Journal 7/1996
St.Laurent, Gilles
The Care of Cylinders and Discs.
Technical Coordination Committee (Ed), Milton Keynes 1997
(available in English, French, German
and Spanish)
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