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Nimbus Records finds a problem with CDs, and recommends that manufacturers change the way CDs are made to keep them from breaking down chemically.
  technofile
Al Fasoldt's reviews and commentaries, continuously available online since 1983

Research shows vulnerability of CDs


By Al Fasoldt
Copyright © 1990, The Syracuse Newspapers
   Diamonds are forever, but compact discs might self-destruct in about eight years.
   That's the startling conclusion reached by one of the world's most respected recording companies, Nimbus Records of England.
   Nimbus did some research on the materials used in making compact discs and reached its estimate of an eight-year lifetime based on calculations, not on actual observations. (CDs haven't been around long enough to test the theory.)
   The problem, according to Nimbus, comes from the need for a reflective layer beneath the surface of the compact disc. This shiny layer is often made from a substance that chemically breaks down, the British company says.
   When that happens, the layer becomes rough or cloudy. This keeps it from bouncing the laser beam back to a window where a tiny eye counts the digital on-and-off pulses picked up by the laser. These pulses make up the digital bit stream of the recording.
   Researchers for other companies have not confirmed these findings, but representatives of two of the largest manufacturers of CDs explained privately that they are taking Nimbus very seriously. Both said they are considering a change in the way they make compact discs, to replace the reflective compound with another substance.
   Nimbus says it has already done that, and has recommended that other companies do the same.
   If Nimbus is correct, many audiophiles are in for a disappointment. For thousands of sound lovers, the primary attraction of the CD medium is not sound quality but the permanence of CDs themselves.
   Compact discs often seem to have an "edgy" taint to their sound, as if the higher frequencies are distorted. But since CDs have been considered virtually indestructible, they are the first choice of collectors who value long-term storage of recordings, even though many hi-fi buffs prefer the sound of carefully made records and tapes.
   Ironically, it may be that vinyl discs, long considered the most fragile current method of storing sound, will last far longer than most experts had suspected. As long as they are kept upright in a dry environment and out of direct heat, phonograph records are now thought likely to last at least a century.
   Even cassette tapes are far sturdier than they used to be. In research carried out in Japan, premium tapes from the three or four major tape manufacturers withstood an amazing amount of abuse without any noticeable effect on the recording. The tapes shrugged off excess heat, shaking, dropping and even stray magnetic fields.
   Researchers credited improved cassette shells and better guidance systems -- rollers, wheels, arms and pins -- inside the shells. They also said the plastic coating that binds the magnetic particles on the tape is more stable than previous formulations.
   Previously, experts at Ampex Corp. had estimated the useful life of magnetic tapes at about 80 years, if they are carefully stored. Even if current cassette tapes last only that long, they could be around 10 times as long as the compact discs in the Nimbus scenario.
   Clearly, if Nimbus is right, it might be wise to record your prized CDs onto cassette and then store the cassettes as insurance. If Nimbus is wrong, at least you'll have copies of those compact discs that you can play while jogging.