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Acetate Phonograph Recordings: Preservation, Storage and Playback
The coating on this "acetate" has been destroyed by corrosion of the aluminum base that got started from a chip or crack. Poor storage conditions and moisture may have accelerated the damage to the point where it likely is not recoverable.

Before the introduction of magnetic tape, radio shows and most recordings intended for broadcast were made on acetate coated discs called "soft cuts" or "instantaneous" discs, or simply "acetates". Most often these were on an aluminum base, but during wartime, many were made with a glass base and were, as a result, extremely fragile, and usually marked as such.

In the case of phonograph records intended for mass distribution, they were plated and metal "stampers" were made from which multiple pressings were produced...the common 78s that we are all familiar with.

Where discs were not intended for more than a few plays, the "acetate" disc was ideal, although they were not as durable as a shellac disc and were easily scratched or otherwise audibly damaged. They were available in the common sizes of 10" and 12" in diameter, but a 16" version was more commonly used for recording radio program material, since they could record over 15 minutes per side at 33-1/3 RPM. A complete show usually was recorded over two separate discs to allow "cueing" the second part of the program for "seamless" playback. Often two separate half-hour shows were contained on the two discs to simplify distribution to the stations. Where masters were required for pressing, an even larger disc of 17-1/4" was used to provide a gripping edge for the equipment that would handle it during manufacture.

To preserve acetates for a long period, they require a little more care than a vinyl or shellac phonograph record. Often they were not given the best of care and many suffer from "cold flow" damage, caused by being piled on top of each other and stored under improper conditions, often in unheated areas where temperature extremes allowed them to freeze and thaw many times during a winter, and summer temperatures could rise to well over 120 degrees. Surface pitting, scratching, chipping, corrosion and other problems all add up to clicks and pops and swishing noises during playback, although for the most part these problems occur near the edges of the discs.

The freezing and thawing causes the acetate to "effloresce", releasing some of its component ingredients in the form of a grayish, greasy, powdery substance that coats the surface and must be removed before any attempts to play the disc. Start with washing the disc in luke warm water with a non-abrasive dish-washing detergent and carefully rinsing and drying, followed by wiping with a folded paper towel pad lightly wetted with household lighter fluid or a dry cleaning solution called perchloroethylene. Wipe with the grooves, never across them, and wipe dry. You may notice a light bluish tinge on the paper towel, particularly if you use perchloroethylene...it is the dissolved efflorescence along with some surface material that you are removing. (It is recommended that you wear latex gloves while doing this to protect your hands since both are powerful solvents and will remove skin oils, and this should be done in a well ventilated area with no open flames or other sources of sparks or fire.)

The chip in the coating of this "acetate" is near the edge of the disc and goes down to the aluminum base and spans 11 grooves. Although it looks bad, it can be tracked with the appropriate cartridge and stylus.

Where poor storage conditions are not an issue, cleaning an acetate disc for playback is easy, assuming that it has been stored carefully in an environment that humans would be relatively comfortable with. Just luke-warm water with a little non-abrasive dish- washing detergent is enough to get accumulated dirt out, and rinse it well to remove any detergent residue. (And remember to always wipe with the grooves, never across them.) A small velvet pad can be used to dry-wipe with the grooves to pick up accumulated dust. Sometimes a light spray of distilled water along with wiping will keep dust and static accumulation down.

Store "acetates" only in a vertical position, never stack on top of each other. Acetate discs are very heavy and the weight, under certain conditions, can cause the "cold flow" damage already mentioned. The relatively soft acetate is distorted by the weight of the discs stacked above them. You may be able to see just such damage on the outside grooves of some discs, caused by the flap of the protective storage envelope being "pressed" into the disc, distorting the surface near the edge, causing a "swishing" noise when played. This noise will be more or less proportional to the amount of "cold flow" that occurred and it cannot be repaired or removed...itís as though it was there at the time of recording.

Play "acetates" with a 2.5 or 3 mil standard stylus. Although you can use a stylus intended for LP records ó and that includes .5 mil, .7 mil and 1 mil styli ó these are mostly too small and ride the bottom of the grooves, often producing a lot of noise and much lower output than the recommended styli. If you are playing "acetates" with a stereo cartridge using the recommended 2.5 or 3 mil stylus, you will often find that playing only from the left channel provides lower noise than either the right channel or both channels played simultaneously.

When you care for an acetate disc as described above,it will last for an undetermined length of time. The writer has acetate discs, cut well over 50 years ago, that play as well today as when they were first cut, and perhaps better, since modern playback equipment can get more out of the grooves than the best equipment available at the time the recordings were originally made.