Re: [ARSCLIST] The ways CD's and DVD's can fail.

[Mike Richter <mrichter@xxxxxxx>]

Charles Lawson wrote:
> Ronald Frazier writes:
> > I honestly think the MAM-A Gold discs are the best in the world at this 
> > time
>
> I, too, still have the best general results with these discs.  However,
> quality control on MAM-A gold discs continues to be an issue for me and
> the problem is growing worse.  I am now averaging five discs per pack of
> 25 that arrive with debris, fingerprints or oily smears on them when they
> come out of the shrink wrap.  I have begun a collection of bad discs to
> return to the factory.  The fingerprints should make tracking the careless
> party pretty simple...
>
> Visually inspect all discs before you plop 'em in your drives...
>
> Caveat emptor,
>
> Chas.

My experience with faulty discs is almost exclusively due to attempts to 
rescue those sent or discussed by others. It appears that the most 
common reasons for disc failure are mishandling and poor original 
recording. In time, the instability of the dyes will come into play, but 
a well-recorded CD-R treated with reasonable care will surely last a 
decade and presumably many decades. I know that error rates do not 
increase noticeably over a decade because I have recordings I made in 
the early and mid 1990s which test today as they did when freshly 
burned: no recognizable increase in C2 errors.

Mishandling takes many forms. Solvent-based markers are known to leech 
through the acrylic lacquer atop the disc; the data lost cannot be 
recovered and often enough the disc will not stabilize in a drive to 
permit sector-level recovery. Some dyes - notably the cyanine and 
phthalocyanine which are otherwise desirable - are more sensitive to 
light and possibly to heat than others; exposing discs with them to 
sunlight for a few hours bleaches out the information. Scratches can 
also be significant, but if severe are easily buffed out.

Poorly recorded discs are vastly more sensitive to failure over time 
than those recorded with low error rate. In an attempt to get 'better' 
recordings, many are writing at speeds below the optimum for a given 
medium and drive with results as unsatisfying as writing above the 
'sweet spot'. For archiving, it seems to me essential that each batch of 
blanks be tested to determine optimum recording conditions and quality 
to be expected when they are used.

It is my advice to those seeking personal archives to consider practical 
issues such as those above before choosing to invest in high-price 
blanks. MAM-A gold may have better life under ideal conditions than a 
high-quality silver disc, but if it is not as well written in your 
drive, the advantage will be lost. At best, the improvement is not 
enough to take shortcuts in other aspects of good practice; one should 
still make two masters on different media to be stored separately. In 
the real world of finite resources, the choice of medium is only one 
factor in the expected life of an archived disc.

Mike
--
mrichter@xxxxxxx
http://www.mrichter.com/