GENERAL

• Never leave recordings near sources of heat or light (especially ultraviolet light) as plastics are adversely affected by both.
• Do not place heavy objects on top of recordings. Recordings should never be placed on top of each other.
• Shelve recordings vertically; do not stack "off vertical" or horizontally.
• Do not use shelving units where supports put more pressure on one area of the recording or where supports are more than four to six inches apart.
• Do not interfile recordings of different sizes as smaller items may get lost or damaged, while larger items may be subjected to uneven pressure.

• Remove shrink-wrap on LPs completely. Shrink-wrap can continue to shrink, thus warping the disc.

• Do not drop tapes. The shock could partially rearrange the ferromagnetic particles, effectively attenuating high frequencies.
• Store tapes away from any sources of magnetic fields.
• Do not store reel-to-reel tapes in a plastic bag within tape box. The plastic bag will trap moisture.
• Handle reel-to-reel tapes by the hub rather than the flanges as the pressure on the flanges will damage them and ultimately damage the tape edges.
• Ten-inch reels should have supports in their boxes so that the hub bears the weight of the tapes rather than the flanges.
• Rewind (exercise) reel-to- reel tapes every 3-1/2 years to work out stresses which may have crept in through linear expansions and contractions.
• Store reel-to-reel tapes with an "archival wind". Wind tapes slowly so that air pockets between layers do not form causing successive layers to be placed unevenly on top of each other. The unevenness will cause stress, expose binder to air and exposes edges to possible physical damage by the flanges.
• A reel-to-reel tape deck with the heads removed can be used to rewind tape in the regular play mode. The tape tension might have to be readjusted to compensate for the removal of the heads.

A proper environment for the storage of sound recording is essential to retard degradation mechanisms. Elevated temperature and humidity can affect certain chemical properties of the plastics that make up recording media and can also create an environment that encourages the growth of fungus. Wide or rapid fluctuations of the environment are equally detrimental to the long term preservation of sound artifacts.

ACETATE DISCS

Shrinkage of the lacquer coating due to the loss of plasticizer is the primary destructive force of these discs. Excess moisture will accelerate plasticizer loss. Acetate discs decompose continuously, and over time react with water vapour or oxygen to produce acids that in turn act as catalysts for several other chemical reactions. One of these is the release of palmitic acid, a white waxy substance. Acetate discs are very susceptible to fungus growth. Excess heat will probably accelerate the loss of the coating adhesion.

VULCANITE DISCS

Vulcanite discs are adversely affected by elevated levels of light, heat and humidity. In response to light and heat, Vulcanite loses sulfur. Light induces oxidation and form oxides of sulfur and sulfuric acid in the presence of humidity. The acidity builds up to a level at which the degrading material is attacked and eventually decomposed. (see reference 15)

SHELLAC DISCS

High humidity levels accelerate the embrittlement of shellac discs. This embrittlement causes a fine powder to be shed from the disc after each playback, effectively scraping away groove information. The severity of the embrittlement is unpredictable, due to the wide combinations and variety of materials (and of material quality) that were used during their production. The average shellac content in a shellac disc is approximately 15 % with the remaining 85% composed of aggregates. Organic materials in the aggregates are susceptible to fungus attack, while shellac itself is said to be fungus-resistant.

VINYL DISCS

Vinyl discs are adversely affected by ultraviolet light and thermal cycling (heat fluctuation). The consequence of thermal cycling is that each cycle of temperature results in a small irreversible deformation, and these deformations are cumulative. (see reference 16) Vinyl discs are resistant to fungal growth and are unaffected by high humidity levels.

TAPES

Hydrolysis is the chemical reaction whereby the binder resin "consumes" water drawn from humidity in the air to liberate carboxylic acid and alcohol. Hydrolysis in magnetic tape results in the binder shedding a gummy and tacky material which causes tape layers to stick together and inhibits playback when it is deposited onto the tape recorder heads. Hydrolysis also causes a weakening in the bond holding the binder to the backing, which results in shedding or possible detachment.

Cellulose acetate backed tapes are very susceptible to linear expansion in humid and/or warm conditions. Because of the different properties of the binder and the base, the absorption of humidity and heat result in tape curling and edge fluttering. Repeated dimensional changes due to environmental fluctuations grossly affect winding tension (hence the need for periodic rewinding) and can promote binder fatigue, cracking, and finally, the irreversible loss of sound information (known as catastrophic failure).

Tape binder is somewhat susceptible to fungi growth though less so with modern tapes as fungicides are presently incorporated into the binder. The process of the break-down of acetate backed tape is exhibited by the release of acetic acid. It is accelerated by the presence of moisture and iron ferromagnetic particles in the tapes. When the acetate is degrading --giving off acetic acid odour-- it starts to take up more moisture. The process of self-destruction is autocatalytic.

CDs

The compact disc is a laminate of 4 different materials. The bottom of the disc is made of polycarbonate onto which the pits containing the digitized sound information are stamped. A thin layer of aluminum is then applied, covering the pits. A thin lacquer coating (which becomes the top of the disc) is then applied to cover the aluminum layer, and finally the ink for the labeling.

As with any laminated products, one must wonder how the aging characteristics of each material will interact with, and affect adjacent layers.

PROPER STORAGE ENVIRONMENT

• Store recordings at a maintained temperature of between no more than 15-20 degrees C. Fluctuation of temperature should not vary more than 2 degrees C in a 24-hour period.
• Maintain a relative humidity of 25-45%. Fluctuation of relative humidity should not vary more than 5% in a 24-hour period. (see reference 17)
• Maintain proper ventilation and air circulation of stacks at all times to avoid any micro climates.
• Keep sound recordings in dark storage when not being consulted. Fit light fixtures with fluorescent tubes which do not produce ultraviolet radiation in excess of 75 uw/lm (microwatts per lumen).
• Separate and isolate from tape vault, any acetate tapes exhibiting an acetic acid odour. Copy the tapes promptly.

Over the past century, recorded sound has become an intrinsic part of our culture. Upon hearing an early sound recording device in 1888, Sir Arthur Sullivan stated that he was "astonished and somewhat terrified at the result of this evening's experiments--astonished at the wonderful power you have developed, and terrified at the thought that so much hideous and bad music may be put on record forever." (see reference 18) Unfortunately, sound recordings are not "forever". These are ephemeral documents, both in their physical composition and consequently in the means by which the sound is ultimately retained. They can have their life span shortened considerably by both internal and external forces. By undertaking certain precautionary measures, custodians of the heritage of sound can lengthen considerably their collection's life span thus preserving a rich, invaluable world of sound.

BIBLIOGRAPHY

ANSI/AES Work Group II. -- Environmental Storage Conditions (Draft 2). January 25, 1991.