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Re: arsclist question concerning research

AES38-2000 AES standard for audio preservation and restoration -- Life
expectancy of information stored in recordable compact disc systems --
Method for estimating, based on effects of temperature and relative humidity
[2000-04-07 printing]


This standard specifies test methods for estimating the life expectancy of
information stored in recordable compact disc systems. Only the effects of
temperature and relative humidity on the media are considered.

----- Original Message -----
From: "Copeland, Peter" <Peter.Copeland@xxxxx>
To: <ARSCLIST@xxxxxxxxxxxxxxxx>
Sent: Wednesday, July 25, 2001 2:37 AM
Subject: RE: arsclist question concerning research

> Dear Donna Campbell and all,
>     Here in the United Kingdom I know no scientific studies of the
> 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
> (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),
> they thought a "noble metal" would have improved longevity. And indeed,
> standard laboratory tests (which always use a "standard atmosphere")
> 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
> (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
> 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
> 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
> 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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