=====
I would definitely put my money on CD-ROM or other technology based on the
5" disc such as DVD or a holographic disc vs. any current magnetic media for
a long term storage solution.
I have never heard delaminating to ever be an expected problem with CDs. I
suppose if they were not made well, the lacquer on the label side could peel
in time, but the data is still imprinted. I would have to see research data
on this to believe it.
=====
Actually, there are several severe problems with both stamped CDs (mass
reproduction) and burned CDs (CD-ROM) which have major impact on the
archival qualities of the medium. Early CDs were printed with ink that
etched the plastic and the foil. It isn't uncommon for most pre-1990 CDs
to have pinholes in the foil caused by the ink. Fortunately, error
detection/correction circuitry is extremely forgiving and "fixes" the
digital audio before converting back to analog. Delamination of the top
layers and foil does occur, but requires extreme environmental conditions
to make it happen. It usually is caused by poor manufacturing more than
anything.
CD-ROMS are very suseptable to problems in comparision to stamped CDs.
First of all, the foil/dye layer is damaged by high intensity UV and IR
light. Don't plan on leaving them on the dashboard of your car on a hot
sunny day. <g> Secondly, the adhesives in most CD-ROM labels are not
archival and neither is the paper. The acids in the paper, ink and
adhesives will eat at the CD-ROMs in most cases. Most of my clients in the
broadcasting/pro audio industry use tiny labels that fit near the spindle
hole or out near the edge, just outside of the last audio/data. They
rarely exceed 75 apacity of the disk either as reliability of the data in
the last 25 0rops a lot.
Has anything improved with DVD? Not really. The technology is pretty much
the same, but the execution is slightly different. Early DVD (another
couple years yet) will have problems crop up that we don't even know about
yet. DVD pretty much just uses smaller lasers, tighter tolerances and data
compression. Otherwise, they are just fancy CDs. Analogy: 5.25" floppy
vs 3.5" floppy.
So how long do we expect CD-ROMS to last? Long enough in the business
world to make it somebody elses problem. Seriously, most of my clients are
figuring a complete archive redo in 15 years. Most have gone kicking and
screaming into the digital archiving arena because of the tape
deterioration problems with AMPEX. They have had to go through tens of
thousands of hours of analog tapes, bake them, copy them and burn them onto
CD-ROM. Unfortunately, much material is damaged and destroyed during the
process and technology/technique hasn't quite evolved enough yet, but we
have had to react quickly. There are two specific problems with audio
tape: Moisture softens the oxide "emulsion" on the tape and rubs off
during playback, and secondly for a period of six or so years AMPEX used an
adhesive that has failed and the oxide "emulsion" literally peels off the
tape. Both are aided by "baking" the tape, but the adhesive failure is a
"single-pass" opportunity.
One interesting thing happened in the industry (pro audio and
broadcasting), they have avoided data files and kept the storage in
standard audio format. File formats change too often and rapidly which
means that you must constantly support all storage formats all the way to
your oldest archive. When you have over 50,000 hours of audio archived, it
is no small task to just "burn a new CD to replace the old one".
Speaking of archiving--I've been looking at some 10-15 year old Kodachromes
and Fujichromes. I'm noticing a color change in those that weren't stored
in "archive quality" sheets--mostly a very slight fading of the reds, but
for the most part they are as good as the day they were processed. Even
so, a little color correction brings them right back into par again. I may
digitize part of the library for "sales" usage, but long-term storage in
digital format seems to be a waste to me as I still will store the
originals anyway. I guess a sort of "redundancy" of my top photos could be
in order, but I'll risk the bulk of my files in analog format vs digital
format anyday.
Ken (vinyl is better for specfic reasons) Norton
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