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Hi
This is based on research made at the National sound archives in Israel by
the late Engineer Avi Nachmias and myself. It was sparked by errors showing
up on CD's that were supposed to be archival grade (Mitsui) and others like
TDK, etc. Different dyes. Too late for me to go into all our findings, and
I'll be happy to present it at ARSC if invited, but yes, some CD's have a
life span of less than two years. Others will last longer, but most will
fail sooner than later. Basically, CD's that are kept in total darkness
with no label attached, that were burnt at X8, or X4 speed will last
longer.

בברכה,
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Cheers
Shai Drori
Expert digitization services for Audio Video
3K scanning for film 8mm-35mm
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On Mon, May 14, 2018 at 9:22 PM, John Schroth <[log in to unmask]>
wrote:

> Hopefully the people at IPI (Image Permanence Institute) at The Rochester
> Institute of Technology are following this thread. I believe they have done
> some longevity laboratory testing on this very same topic. I've written
> them on this thread just in case.
>
> From what I know, optical disks with a gold reflective layer are somewhat
> of a misnomer. A gold reflective layer only helps to keep the reflective
> layer from oxidizing if there is separation of the disk layers that lets
> air get to this layer and oxidize it (some call this disk rot). What's more
> important is the chemical composition used for the photo-sensitive dye
> layer and to what level of permanence will this layer have.
>
> I've also come across quite a few disks, both DVD and CD writable, where
> contamination of oils/other substances have leached through the protective
> underside layer and rendered the disk unplayable either in part or in
> total. So one might have the best disks you can buy and mishandling the
> disk unknowingly, may effect the life of the data on the disk.
>
> I believe this is the report I saw years ago on this topic. An interesting
> read: http://www.stilcasing.com/pdf/CDandDVDCareandHandlingGuide.pdf
>
> Kind Regards,
>
> John Schroth
>
> MTS
>
>
>
> On 5/14/2018 1:34 PM, Eli Bildirici wrote:
>
>> I'm very far from an expert but I was under the impression that it's
>> difficult to generalize. There are 'known good' stocks that last longer
>> than avg - beyond the sort billed as medical grade, archival, gold, etc -
>> and the converse. And of course this has been a moving target over the
>> years because dye compositions change, companies go out of business or get
>> acquired (most recently JVC-Taiyo Yuden) or give up on the market, etc.
>> There are some known awful makes (e.g. Princo or Moser Baer) that you might
>> expect would last for less than usual but I've got some that will still
>> read and aren't warped or anything. Generally I remember hearing that azo
>> dyes are worse than cyanine but I do not have a study handy to back this
>> up. How they are kept is probably also relevant.
>>
>> I have found that a good resource for these kinds of questions are the
>> media (https://club.myce.com/c/blank-media) and burner (
>> https://club.myce.com/c/cd-dvd-and-blu-ray-writers) subforums at myce.com
>> (formerly known as CDfreaks). There are still maybe ten people there
>> actively doing testing (using proprietary tools like CD-DVD Speed/Opti
>> Drive Control and a battery of drives that are compatible with those
>> programs) of new and NOS stock and a few that have been around since the
>> early days there. That is not a study, plural of anecdote is not data, etc.
>> But if anybody knows of those studies, they would, and their cumulative
>> experience should still count.
>>
>> May 14 2018 1:08 PM, "Steven Smolian"  wrote:
>>   At the just concluded ARSC conference, one of the presenters said that
>> the
>> expected life of a CDR was 5 years. Perhaps it was Maya.
>>
>> At any rate, is there a study underlying this comment?
>>
>> Am I correct in assuming this does not apply to medical-grade gold CDs?
>>
>> Steve Smolian
>> Eli Bildirici
>> (347) 837-8337
>>
>> ---
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>>
>>