Re: [ARSCLIST] delamination of CDs

[Jerome Hartke <jhartke@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx] On Behalf Of George Brock-Nannestad
> Sent: Thursday, July 07, 2005 3:50 AM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: Re: [ARSCLIST] delamination of CDs
>
> From: Patent Tactics, George Brock-Nannestad
>
> Bev Lambert wrote:
> > >I am not a preservation scientist or even an knowledgeable audiophile,
> but an
> > >archives conservator charged with the task of researching best
> practises for
> > >digitization of magnetic media.  So, my question may seem naive: is it
> known
> > >whether CDs are laminated with an adhesive?  and if so, is it known
> which
> > >adhesive this is?  It seems to me that a different process. such as
> heat or
> > >pressure lamination would be more appropriate?
>
> ----- several persons responded - apparently correctly - that there are no
> adhesives used in the lamination process for CDs. However, for the CD-R to
> be
> able to tolerate handling, there has to be adhesion between the various
> layers. If the strength in the interface between layers (adhesion) or in
> the
> material internally (cohesion) is not sufficient for the purpose, then the
> laminate separates. That could potentially be the case in the
> phthalocyanine
> layer that separates the polycarbonate from the metallization. I have no
> reports of such a thing happening, but on the other hand, very few people
> have first-hand experience of phthalocyanine as a house building material.
> I
> have myself _unsuccessfully_ tried the Scotch-tape test (using a high-
> grade
> tape) to separate the polycarbonate sheet from the deposits.
>
> Kind regards,
>
>
> George

Although delamination is a potential risk, we have never observed it on
regular discs. Our lab has tested thousands of CD's over many years,
including storage at elevated temperature and humidity levels. We did
observe it once while evaluating an experimental coating for a manufacturer.
Needless to say, that coating was never used in production.

In reality, we have seen many, many examples of poor user handling.
Scratches, smears, fingerprints, and debris are frequently present on
surfaces of discs that "mysteriously" skip or have other read problems.

Storage in paper sleeves instead of jewel cases is another problem, since
paper is abrasive and induces very fine scratches every time the disc moves
within the sleeve. Although these scratches may not be apparent, their high
density can act as a diffraction grating that distorts the beam.

It is best to focus on issues that can be controlled by the user, and not
create others that cannot be controlled and may not be real. We often see
"bad" discs that result from a poor quality writer or have been recorded at
high speeds. Recording software often creates discs having volume and file
structures that do not conform with ISO 9660. Yet archivists seem to seek a
"magic" brand of disc that will solve all problems. This does not exist, and
confidence in interchange and longevity can only be achieved through
testing.

Jerry
Media Sciences, Inc.