Re: [ARSCLIST] New CD Report NIST

[Jerome Hartke <jhartke@xxxxxxxxxxxx>]

As mentioned before, BLER alone gives misleading results for accelerated
aging as reported at http://www.mscience.com/longev.html

Jerry
Media Sciences, Inc.

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx] On Behalf Of Joe_Iraci@xxxxxxxxx
> Sent: Monday, December 13, 2004 10:07 AM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: Re: [ARSCLIST] New CD Report NIST
>
> 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