Re: [ARSCLIST] Gold CDs

[Joe_Iraci@xxxxxxxxx]

Stability of CD-R media is dependent on three variables:  metal reflective
layer; top protective lacquer layer; dye type.

A good quality lacquer layer applied properly will provide physical
protection for the vulnerable metal layer beneath it and prevent or at
least slow significantly penetration of oxidizing reagents from the
atmosphere into the disc structure.

Gold will not corrode and therefore is recommended for optimum stability.

The third variable is the dye.  Phthalocyanine is the most stable dye and
therefore, along with the other two criteria mentioned above  -- is a must.

Some recent accelerated aging experiments I have performed (paper to be
published soon) ranked the CD-R with phthalocyanine dye more stable than
any other CD-R or DVD-R format.

Joe Iraci
Senior Conservation Scientist
Canadian Conservation Institute



             Steven Smolian
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             23/09/2004 05:14
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I'd like to propose an archival practice.

The weakest spot regarding the longevity of recordable CDs is the lacquer
surface.  Fissures allow oxidization of the reflective surface.

Reinforced lacquer surfaces have become available.  This reduces the
surface vulnerability somewhat.

Gold does not oxidize.  All other products used to reflect the laser light
will oxidize.

Recordable CDs are available with gold reflective surfaces and hardened
lacquer surfaces.

It seems to me that a gold reflective surface should be the accepted
practice for any CD-R made for preservation purposes.

Lacquer reinforcement of the top surface is an added protection.  Gold,
however, should be considered essential.

Labeling of CDs should be clear when indicating if gold has been used or
merely gold coloring added to another reflective product.  I saw some of
the latter in a computer store recently.

Steve Smolian