Re: [photo-3d] CD-Rs = 200 years?

[Brian Reynolds <reynolds@xxxxxxxxx>]

Tom Deering wrote:
> On 6/17/00, Andy Beals wrote:
> >> I'm concerned that there isn't a digital storage medium
> >> currently available that will safely retain images for the
> >> long term.  I believe CDRs are supposed to be good for about
> >> 12 years if stored in ideal conditions.
> >
> >I think you're off by a factor of ten, there.
> How long is the life span of a CD-R?
> 
> The life span of a recordable disc depends on several things:
> 
> 1.   Color of disc: most makers of CD-recordable discs claim that the 
> green (cyanine) discs last up to 75 years, gold (phthalocyanine) last 
> up to 100 years and the silver-blue platinum last up to 200 years. 
> See the manufacturer's information.
> 

There are a few things to take into account with these numbers.
First, they were reached with accelerated testing procedures.  If the
testing procedures do not actually match real world conditions
(perhaps they for got some factor, or the conditions the test
simulates change over the time span they are projecting) the results
aren't good.

These numbers should be taken as an upper limit, not as the average.

> 2.   Environmental factors: the lifetime of the disc may be reduced 
> if is exposed to water, sun, or heat. Treating your recording media 
> carefully will extend its life expectancy.
> 

This is the biggest factor.  Most of these test are reported for
environmental conditions used by museums and archives.  That means
storage at a controlled (low) temperature and relative humidity in the
dark.  Almost no users of any of these products (film, paper, inks,
and other media) will store their work under these conditions.

It is possible to interpret the test data for other storage
environments, but generally the people who pay for, or perform, these
test are not willing to release the data.  (Remember "120 years before
noticeable fading when stored at 50 degree F, 50% relative humidity
and less than 400lux" is an interpretation of the data, not the data
itself.)

> Above from http://burningcd.com/faqs.html#span
> 

These are hardly a disinterested third-party, and they do not cite
there references.

I would not trust the testing done by a manufacturer.  Testing needs
to be done by a third-party in order to ensure that the results
haven't been fudged.  Wilhelm Imaging Research
<URL:http://www.wilhelm-research.com/index.htm> has done independent
testing for several manufacturers, and there are a few archives that
also do testing.

This has been thourghly discussed on the epson-inkjet 

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
reynolds@xxxxxxxxx              | "Oooh!"
http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
NAR# 54438                      |       "Dexter's Laboratory"