CD-rom longevity

Rab Jackson <pr258rj [at] admin__nls__uk> writes

>I have had a request from a colleague who is concerned about the longevity
>of CD ROM.

There are two issues here. Factory pressed CD-ROMs will last about
as long as a similar quality factory pressed music CD. There are
differing projections as to the life of CDs. A common figure spoken
of by manufacturers is 100 years. A study from a couple of years ago
by Australia's National Film and Sound Archive (NFSA) suggested a
minimum of about 38 years and a maximum of about 77.

At the Joint Technical Symposium (JTS--joint meaning the technical
committees of the international associations of Sound, Film and TV
archives) in London in January 1995 a paper was delivered on the
breakdown of conventional CDs and the French specialists who
delivered the paper believed that it was the "plastic" coating that
was the greatest danger. Earliest coatings were nitro-cellulose and
it was suggested that these would last 15-20 years. More recently
polyacrylic and UV-cured polyacrylic coatings have been used--these
would last longer they said. Unfortunately the proceedings of the
conference have not been published and I was not at the JTS.

Recordable CD-ROM (ie. CD-R) uses a different manufacturing process.
Manufacturers claims vary. Kodak say that their accelerated ageing tests
indicate that their Infoguard CD-Rs will last 219 years. TDK on the other
hand say that their discs will last as long as a conventional
CD---i.e. "about 100 years". There has not been a lot of independent research. Work
done by West Deutsche Rundfunk in Germany supports the claims of CD-R
hardware and software manufactures, though they were thinking more in terms
of the claims made 2 or 3 years ago of 10-20 years as the life of a CD. The
NFSA's study was not as generous as some, suggesting a life expectancy of
10-20 years.

Just as--to use an Australian advertising slogan--"oils ain't oils",
neither are all CD-Rs the same. Dye technology is a crucial factor in CD-R
manufacture and I believe that Kodak have a very good proven track record
in dye technology. But more and more R & D money is being poured into CD-R.
This augurs well for its future I believe.

But how long is the CD-ROM format going to last? This is perhaps a more
important question.

John Spence
Head, Radio Archives
Australian Broadcasting Corporation
Sydney NSW
Australia

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                  Conservation DistList Instance 9:11
                 Distributed: Wednesday, July 19, 1995
                        Message Id: cdl-9-11-010
                                  ***