Re: [ARSCLIST] New CD Report NIST

[Joe_Iraci@xxxxxxxxx]

I have performed a similar study that will be published in Restaurator in
early 2005 (I will pass on the reference to the list once it is published).
Accelerated aging was performed on CDs, CD-Rs (various dye types), CD-RWs,
DVDs, DVD-Rs, DVD-RWs.  Many (much more than the NIST study) different
types from different manufacturers were tested.  Results were based on BLER
changes.  Conclusion was that the CD-R with phythalocyanine dye
outperformed all other disc formats.  A relative stability ranking of the
various formats was produced.

The goal of the study was to assist individuals in making choices when it
comes to optical media.  Making a  lifetime prediction is time consuming,
expensive, and usually contains a lot of uncertainty.  I believe a more
practical approach is examining relative stabilities.  Any study that
provides information on how this media reacts is useful.  Granted reactions
are occurring at higher temperatures and there is no guarantee that those
same reactions will occur at room temperature, but if you had to choose
would you trust media that withstood harsh accelerated aging (80 degrees
Celsius and 85% relative humidity for intervals up to 84 days) and still
had no E32 errors and low BLER or media that failed within the first 21
days under these same conditions.

Yes, there are other factors to consider like writing speed and
compatibility issues, but the focus is on media stability in this case.

In the above study, using either BLER or E32 errors would have led to the
same conclusions.  BLER alone can sometimes be misleading, but generally
not when it comes to monitoring degradation via accelerated aging.   As
long as both are monitored I do not see a problem using BLER. This
observation is based on the experience of aging and analyzing several
hundred discs.  Same applies to PI errors for DVDs.

Joe Iraci
Senior Conservation Scientist
Canadian Conservation Institute