Longevity of CD-R (was RE: Preserving Newspaper.)

From: Eric Smith <eric_at_brouhaha.com>
Date: Sun Nov 10 19:36:00 2002

> Of course CDR media is supposed to have a 20 year life span (vs. the
> Sony advertised/hyped 100 years)

I'm not sure I'd even count on twenty years for silver CD media. Oxygen
seeps in and oxidizes the reflective layer, reducing the contrast
ratio well below what a drive can discern. I've seen this happen to
poorly made audio discs in less than ten years, and there's no reason
to believe that cheap CD-Rs are any better.

Gold media (with an actual gold reflective layer, not just gold-tinted
dye) should last over 100 years. Kodak did accelerated aging tests and
found that 100 years was a reasonably conservative estimate. They
used to have a detailed white paper on their web site, but it doesn't
seem to be available any longer.

Of course, it is always possible that there is a failure mode that
is not modeled accurately by accelerated aging tests.

I'm completely unimpressed with the newer Kodak gold and silver mix.
There's not enough gold to see, so there's not enough that a drive will
be able to see it after the silver oxidizes. Unless there's some
pretty amazing chemistry going on in there.

Kodak seems to be mostly out of the gold CD-R business, but Mitsui and
Taiyo Yuden still make gold media. It's hard to find at retail, though
a Google search turns up plenty of mail order sources. Of course it
is much more expensive than silver.

I have a supply of Kodak gold media I use for discs I intend to keep
for archival purposes. For everything else I use silver media. For
a few years I've been buying TDK spindles of 50 discs at Costco. The
media was made by Taiyo Yuden and was quite good as silver discs go.
Unfortunately the last time I tried to buy some, they only had TDK
100-disc spindles. Not realizing that the media was different, I
bought one, and was appalled to find that about 20% of them were bad.
The ATIP data indicates that these discs were manufactured by CMC
Magnetics, one of the *worst* manufacturers. I can't believe that
TDK switched from the best to the worst!

Now I'll probably start buying bulk-packaged Taiyo Yuden discs by
mail order.

Eric


Eric
Received on Sun Nov 10 2002 - 19:36:00 GMT