PDA

View Full Version : Shelf life of DATS and CD's??


TMS
10-29-1999, 09:29 AM
I'm sure most of us have seen old analog tapes turn to goo and have to resort to baking them in ovens and so forth to try and bring them back to life.

Question:
If properly stored, how long is the shelf life of DATS? Has there been any formal research on this? For that matter, I have heard vareying opinions on how long CD's will last before starting to decompose and that is why large corporations will not archive data on them for long term.
Just wondering

Craig

dBHEAD
10-29-1999, 10:56 AM
I've always heard that tapes are worthless after 20 years, but I have several tapes from my radio days which are about 22 years old and they still sound quite good with wide frequency response and excellent stereo separation. What's more, these have never been stored under ideal conditions. In fact, they spent the better part of a year in the trunk of a car which was parked outside and went through extreme temperature and humidity changes. You CAN hear dropouts, but they're minor. Only an audio pro would notice them.

I've heard CDs were supposed to last for CENTURIES. Unlike tape, which is susceptible (sp?) to any form of electro-magnetic radiation, CDs have physical pits burned through a reflective surface by a lazer. The CD can only degenerate when the reflective surface starts to crack in tiny chips or the pits start to get filled in with microscopic debris. If the CD is properly protected, it theoretically could still be playable in thousands of years.

I can speak with authority about magnetic tape. I can't say that my understanding of CD archiving is totally correct but I believe it's pretty much in the ballpark.

coaster
10-29-1999, 11:04 AM
i have had da88 and dat tapes which appear normal to the eye but develope severe error rates if they sit too long, even well cared for tapes. scary.
if i understand correctly, the aluminum layer in a factory cd is where the information is stored. the reason this layer goes bad is due to an extremely minute exposure to oxygen in the manufacturing process. or is this true? i have old cd's that are fine. i don't own any cd's that wont' play with a little coaxing. i have not had enough time to know the shelf life of a cdr, all of mine still function, however several digital tapes are unuseable.

TMS
10-29-1999, 04:12 PM
<<<if i understand correctly, the aluminum layer in a factory cd is where the information is stored. the reason this layer goes bad is due to an extremely minute exposure to oxygen in the manufacturing process.>>

This is also what I have heard. I've also heard that there are or where archival type cd's that had a gold type layer but that they were EXTREAMLY expensive. As far as twenty year old analog tapes go, I had an old SFX (1/4 inch nagra) collection that was stored properly and I had to bake them to rescue them. I am also starting to hear horror stories regarding dats. I guess precious sounds should be stored on several mediums like dat, cd etc.

Of course, twenty years from now we'll have to go to a museum to find something to play them on.

Craig

ProTool1
11-01-1999, 10:09 AM
<<<if i understand correctly, the aluminum layer in a factory cd is where the information is stored. the reason this layer goes bad is due to an extremely minute exposure to oxygen in the manufacturing process.>>

Incorrect.

The information in a factory cd is stamped
into the upside of the plastic (reversed of course so when reading from the bottom it is forward) and the "aluminum" (not really aluminum) is simply a device to reflect the laser with the information back to what reads it. This proccess for making a CD makes it a very reliable source for data storage for a very very long time.

CDR's- CDR's as we all know are burned, not stamped. You will notice with all CDR's that they have a distinct color to them, usually a bluish color or sometimes more of a gold color. This color that you see is actually a sort of powder that lies between the shiny "aluminum" layer and the plastic of the disc. This powder is what the information is burned into.
If you do not buy a quality CDR, I mean a REAL quality CDR, such as the ceramic plated
BASF (my favorite) or another of the same caliber, you can run into problems with log term storage. The shiny film on cheap CDR's is very suseptible to oxygenation, causing it to become brittle and chip or flake away with ease, and without this shiny layer, you have nothing to reflect the laser back to your player with the information. Therfore a bad disc. I have had cheap CDR's do this in just a few short months. Beware.

Hope That helps a bit http://www.digidesign.com/ubb/images/icons/smile.gif

Sydney
11-01-1999, 01:32 PM
"Using high quality DAT tapes should yield >30 years of shelf life."


What is the archive life of a CD-R?

"Cd-R's are coated with different recording dyes--all with varying life expectencies. Phthalocyanine (Gold) dyes can hold data for an excess of 100 years--much longer than the expected 10 year life of Cyanine (Green) dyes. Cyanine is very sensitive to sunlight. Archive life mainly depends on the care you take of your CD's, both with storage and with handling."

I got the above info from the HHB "A guide to choosing and using digital audio recording media" booklet. Lots of neat info on where all of the various digital formats came from and how they work.

Hope that helps...

Drew

nipple
11-01-1999, 02:37 PM
>>"Using high quality DAT tapes should yield 30 years of shelf life."<<

I don't think so. DAT is absolutely the worst medium I've ever seen. Even with the highest quality tapes I've seen dropouts etc.. after only a few years of storage. Also, they sometimes will not play back properly on other machines. I avoid using it unless I'm forced at gunpoint.