4. Handling, storage and preservation
In presenting the arguments for high standards in recording we saw that sound recordings, unlike written records, contain no superfluous matter but that every detail is a source of information. In a book, a spot of fungus on a page will generally not hinder the reader and at worst may reduce the volume's commercial value, but the slightest damage to a sound recording immediately results in a loss of information. Its physical vulnerability dictates the precautions which we need to take if we are to ensure the preservation of acoustic source material. 1
Before considering other risks to sound carrying media we must first consider the problems of decrease in quality as a result of normal use. Disregarding the damage done to recordings by careless handling, the loss of quality through normal use is relatively high in the case of mechanical sound carrying media. Because of the friction between stylus and record, with time the groove becomes worn and the signal distorted. The degree of wear and tear involved depends on various factors, but above all on the condition and adjustment of the record player. The recorded signal and the material of which the record is made are also important factors, so that no matter how careful one might be the risk of damage can still be relatively high. These risks are appreciably less in the case of magnetic recordings and, provided excellent playback facilities and modern tapes are used, it is safe to say that changes in the signal in normal playback will be minimal. There is always the danger that tape oxide might sometimes be rubbed off, especially when older tapes are wound at high speed. In particularly bad cases one must take special care by making safety copies, but generally it is sufficient simply to wind at a slower speed.
The effects of temperature on sound carrying media depend on the material involved. In the case of shellac and modern vinyl records and the nowadays rather rare PVC tapes, temperatures above 500 C are considered a risk. The old acetate tapes, which are no longer produced, and the modern polyester tapes can withstand temperatures well over l000C. High temperatures, however, will increase print-through on tapes and continual changes in climatic conditions are also to be avoided; the optimum temperature for an archive is 200 ± 30 C, although print-through can be kept to a minimum in rarely used stores for security copies by keeping temperatures at a level of 100C. It should also be noted that heating devices, lighting and sunlight can also be damaging, even when temperature controls are used. The field researcher operating in tropical climates can provide some protection for his tapes and films by keeping them in polystyrene containers.
Only shellac records are immediately at risk from high humidity. The old acetate and cellulose tapes, on the other hand, shrink and warp if storage conditions are too dry. Micro-organisms such as fungus thrive in high humidity and quickly attack both magnetic and mechanical sound carrying media altering the surfaces to such an extent that the record content may be partially or even totally ruined. Relative humidity should therefore be kept to a level of 50% ± 10%. Humidity is particularly important to researchers working in tropical regions, where valuable original recordings can be protected by frequently exposing them to the air and storing them together with moisture absorbent silica gel.
On records, dirt in its many forms produces the well-known crackle effect. With tapes it leads to 'drop outs', as the contact is lost between tape and tape head. Dust should, therefore, always be avoided and, equally, one should never touch the surface of a record or tape as this can also cause dirt to stick to it. Adhesives of all kind, especially inadequate splicings, should be removed if present and otherwise generally avoided. Before adopting a particular method of cleaning record or tape surfaces, one should always make a thorough check of the available literature on the subject and test the methods properly beforehand. Good packaging, properly sealed work rooms, archive areas which can be easily cleaned and with dust filters fitted to climate controls should provide a good protection against dust.
Defective spools and uneven winding can cause tape warping as also can bad packaging and incorrect storage. Both records and tapes should be stacked absolutely vertical when in store; if they are kept in a leaning position for long periods, they can become permanently warped and so this too should be avoided. Records may also be stored in suspended position, while any inserts - such as textual material - which can cause them to warp, should be kept separately.
A well-known and, as we shall see, over-rated cause of damage to tapes in store is the occurrence of print-through. This term is used to describe the echo effect resulting from magnetic interaction between two adjacent layers of tape on a reel, thus producing the effects known as pre-echo and post-echo. The degree of print-through mainly depends on the characteristics of the individual tape, on tape thickness, temperature and period of storage. However, the echo signal - unlike the basic recording signal - is unstable and can easily be greatly reduced by mechanical means, such as rapidly rewinding the tape. This is confirmed by the results of recent tests. 2 The problem of print-through, therefore, is one which can be ignored as long as tapes are chosen and stored correctly, are rewound once a year and kept alternately on the take-up spool (or 'tails out' position) and the feed spool (or 'tails in').
One should not underestimate the dangers to tapes from magnetic fields. Tapes should, therefore, be kept well away from dynamic microphones and headphones, as well as from loudspeakers and electronic measuring instruments. Permanent magnetic fields, which are a particular risk to tapes during play-back, can also build up on tape heads and tape guides. Regular demagnetisation is, therefore, a vital part of any service schedule. One should also make certain when fitting out storage areas that there are no high voltage electricity cables, power transformers or lightning conductors in the vicinity which might be dangerous sources of magnetic fields.
To complete the picture, it must also be said that one should consider not only the specific problems mentioned above, but also the more general ones such as security against theft, fire and flooding.
- Because this chapter is only meant to serve as a basic guide, only the most important sound carrying media have been mentioned. These are:
Mechanical recording media (records):
shellac records (78 rpm records)
vinyl records (LP records)Magnetic recording media (tapes) with the following base materials:
acetate-cellulose (AC, no longer used)
polyvinylchloride (PVC, rarely used)
polyester (PE)
- Schüller, D. 'Archival tape test' in Phonographic Bulletin, No. 27; 1980
