RE: arsclist question concerning research

["Copeland, Peter" <Peter.Copeland@xxxxx>]

Dear Donna Campbell and all,
    Here in the United Kingdom I know no scientific studies of the longevity
of manufactured CDs, only of Kodak's CD-R discs which I have already
mentioned on this listserver.
    However, you might like to note this piece of "anecdotal evidence"
dating back to the earliest days of CDs. The Philips Dupont Optical factory
(PDO) in Blackburn, Lancashire, was the first to make compact discs in
Europe, having previously made analogue "Laservision" discs. From Day One,
they decided to use silver for the reflective layer (not aluminium), because
they thought a "noble metal" would have improved longevity. And indeed, the
standard laboratory tests (which always use a "standard atmosphere") confirm
this.
    Unfortunately, a "standard atmosphere" does not include any sulphur
(sorry about my English spelling!) There are literally millions of tons of
sulphur in the atmosphere, usually in the form of sulphur dioxide; but I
understand the critical compounds are sulphur trioxide and hydrogen sulphide
(which can occur naturally as a result of lightning strikes, let alone
modern industry). These gases eventually permeate between the molecules of
the polycarbonate, and turn the silver brown (silver sulphide). This begins
to turn a CD noticeably brown after five years or so, and it usually stops
playing altogether after about ten years.
    I must report that PDO realised this problem, and very promptly offered
a free replacement service for affected discs. In fact, once a particular
issue had been affected, they knew they would have to institute another
pressing-run; so they made a thousand (I think it was) of all reported
discs, so they could send a replacement by return of post. Consumers were
asked to retain the jewel-case and inlay-card. (As with LP discs, the
documentation cost much more than the audio)!
    This seems to affect CDs made in the years 1981-1983 or thereabouts;
PDO's initials usually appear near the centre-hole.
Peter Copeland
<peter.copeland@xxxxx>

-----Original Message-----
From: Campbell, Donna [mailto:drcampb@xxxxxxxxxxx]
Sent: 24 July 2001 19:38
To: 'ARSCLIST@xxxxxxxxxxxxxxxxx'
Subject: arsclist question concerning research


Hello,

Does anyone know of any published or on-going formal research focusing on
the longevity of CDs?  Since about 20 years have elapsed, I was wondering if
anyone was studying the quality of the earliest releases of compact discs.
I have conducted some preliminary research of literature and have found no
indications of such research.

Thank you,
Donna Campbell

~~~~~~~~~~~~~~~~~~~~~~~~~~<>~~~~~~~~~~~~~~~~~~~~~~~~~~
Donna Campbell
Library Catalog Specialist III
William & Gayle Cook Music Library
(812) 855-2970



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