Re: [ARSCLIST] Optical disc "repair"

[Tom Fine <tflists@xxxxxxxxxxxxxxxxxxx>]

If this sort of machine can buff out the kind of circular or "horizontal" gouge/scratch that makes a 
music CD partially unplayable (ie more errors than can be corrected) or data un-recoverable, than 
it's worthwhile to fix those discs and then COPY THE CONTENTS TO A MANAGED STORAGE SYSTEM AND/OR 
ANOTHER OPTICAL DISC. As far as using one of these machines, making the data recoverable/playable 
and then assuming "problem solved," well I think that's probably not a the best plan. Here are a 
couple long-term factors I'd be concerned about:

1. does the polishing process skim off some sort of an air barrier, this allowing quicker oxidation 
of the metal layer or contamination of the dye layer on a CDR? I'm not saying this would happen 
anytime soon but it might be an archival-length issue.

2. does the machine itself, either by how it holds the disc or by the vibration and pressure of the 
polishing process, in any way squash or damage the metal layer or alter the dye layer? Again, this 
may or may not be a short-term problem but might matter over years or decades. Also, even if 
immediate damage is done to one part of the disc -- for instance causing more correctable errors in 
region "a" -- but the problem of uncorrectable errors is solved in another part of the disc, then 
the net result is probably positive. Perhaps one safeguard would be to recover as much data as 
possible in a pre-buffing pass and then recover in a post-buffing pass and use some sort of software 
to compare results and keep least-corrected-error data.

I'll tell you, public library systesms sure could use this sort of machine. I get about 1/4 of 
circulated CD's with unplayable regions.

-- Tom Fine

----- Original Message ----- 
From: "Marcos Sueiro Bal" <mls2137@xxxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxxxxxx>
Sent: Thursday, February 07, 2008 11:01 AM
Subject: [ARSCLIST] Optical disc "repair"


> On my way to work this morning I was intrigued by a poster in the local game shop advertising CD 
> and DVD "mail-in" repair. I went to the web site listed. Take a look around; it is fascinating, 
> among other things because it is directed towards dealers selling the process.
>
> http://www.azuradisc.com
>
> I have heard at least one expert in optical media state that all of this burnishing systems are 
> actually damaging the polycarbonate layer and are harmful in the long run, but I wonder if there 
> are any papers showing any reduction of errors after this kind of process (good luck finding links 
> to such a paper in the web site above). If so, could process like this one be compared to, say, 
> baking of tapes? In other words, "get the data to another medium while you can"? (But note that 
> this is not what they advertise in the web site; they advertise actual repair of the disc... it 
> will be like new!)
>
> There are accessories sold by this company (e.g. foam for your jewel case?!?) that make me 
> suspicious, but I am not ready to condemn their whole process yet. I am curious to hear reactions 
> or comments from other posters.
>
> Cheers,
>
> Marcos Sueiro
> Columbia University