Re: Re[2]: [AV Media Matters] Polishing of CDs

[lanyap@inlink.com]

Hi Mr. Iraci,

Would you be so kind as to briefly define or explain the terms BLER and E32
& how the measurements are made.  To date we have only subjective
evaluations showing very positive results with no reports of damage when
our minimalist polishing system is employed.  We'd be glad to send you
materials to evaluate in an objective manner upon request.

Thanks for your time,

Duane Goldman

At 07:00 AM 8/10/00 -0700, Joe_Iraci@pch.gc.ca wrote:
>I have performed some brief experiments on CD polishing as part of the work
>that
>I am doing on the disaster recovery of CDs.  One of the scratch remedies
>studied
>was the Fix-a-Disc polishing system.  Scratched and unscratched discs were
>examined with the results summarized as follows:
>
>Read-only disc with no scratches.
>The disc was unaffected by the scratch removal procedure.
>
>Recordable CD with no scratches.
>The disc showed an increase in BLER (1.8 to 12.9) and E32 (0 to 43494).
>Also, a
>3.5 minute portion of the disc could not be analysed at all.
>
>Audio CD with significant scratches and playability problems.
>With the scratch removal the disc got worse: BLER (44.6 to 59.9) and E32
>(648 to
>84013).  After a long polishing time all the scratches could not be
removed.
>
>Audio CD with significant scratches and playability problems.
>This disc showed improvement: BLER (72 to 59.9) and E32 (26332 to 1955).
>However, deeper scratches were still evident.
>
>A fifth disc initially could not be analysed but after scratch removal it
>could
>be studied.  However, the disc remained in poor shape with E32 at 10799 and
>deep
>scratches still evident.  Polishing the disc for several hours with the
>highest
>grit paper could not remove all of the scratches.
>
>Therefore, from this small study it is evident that polishing appears to be
>hit
>or miss.  It may improve scratched discs to some degree but may also make
>discs
>worse.  This was especially evident in the unscratched CD-R that was put
>through
>the process (as a control).
>
>Some other scratch removal solutions (plastic polishes, metal polishes,
>commercially available polishes for CD repair, and others) were also tried.
>The
>results for the mild abrasives were variable as indicated below:
>
>Of the 21 discs tested with the various remedies 33% showed no change, 24%
>showed an improvement and 43% were worse after treatment.  Essentially half
>the
>time the treatment resulted in a disc that was worse off than the original.
>Once again scratch removal treatment in this way should be used as a last
>resort.
>
>Joe Iraci
>Conservation Scientist
>Canadian Conservation Institute
--
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