storage of cds

Subject: storage of cds
From: The Sandman
Date: 20 Jan 08 - 07:56 AM

what are the ideal temperatures and conditions for storing cds?and will temperature/humidity effect their longevity?

Subject: RE: storage of cds
From: cptsnapper
Date: 20 Jan 08 - 12:09 PM

One thing which might help you is the Corrosion Intercept technology: for further details contact http://www.conservation-by-design.co.uk/

Subject: RE: storage of cds
From: Peace
Date: 20 Jan 08 - 02:24 PM

Article you should read.

Subject: RE: storage of cds
From: JohnInKansas
Date: 20 Jan 08 - 03:22 PM

And add to the list of do/donts in the article linked by Peace:

"Check regularly for updates in archiving methods, standards, and media life."

The article was written in 1996 and doesn't appear to have been updated. While the recommendations in the article are still good there have been some slight changes in CD formats and technology.

The recommendations for "archival CD manufacturers" probably are outdated; but since it's almost impossible to get blank CDs in special "archive grades" now for home recording it's likely an "academic point" for most.

Some "manufacturers" claim that accelerated life testing indicates reliable data retention to 50 years or more now (with proper storage), but when you buy a particular retail brand (or brand-line) you have no way of knowing who actually made the disks or what dye/base/layer methods were used, since all the "manufacturers" are actually "resellers" who switch sources frequently and without notice. It still helps to stick with a "major supplier/brand name" since the ones who want to keep a good reputation usually do impose more and better quality control testing and verification than "discount" or "unbranded" suppliers.

If you're accumulating enough "valuable" CDs to merit serious concern about archival life, it's probably almost equally important that you be very concerned about having a method of indexing what's on the disks and finding the one you want. It doesn't make much difference whether the disk is good or gone, if you can't figure out which one you want and find it in your collection.

John

Subject: RE: storage of cds
From: Peace
Date: 20 Jan 08 - 03:24 PM

Thank you for that post, John.

Subject: RE: storage of cds
From: JohnInKansas
Date: 21 Jan 08 - 07:59 AM

If anyone finds any comparative data on the durability of CDs vs DVDs (for the home recordable ones) I suppose it might be of interest. Due to the much more sensitive "recording" layers required for the DVDs I'm a bit dubious that they'll be comparable to CDs for long term stability - as currently available; but real data would be helpful.

I've found some format problems with using DVDs for data backup - esp. because data recovery is extremely slow and clumsy, so I haven't used them much, even where "long-term data security" wouldn't be much of an issue. Suppliers seem to hope that users will assume they're the same, but the absence of actual "competent affirmative statements" on the issue keeps my suspicions nagging at me.

For now I've only got about 600(?) backup data CDs on the shelf, so it's not a big problem, but higher data-density might be helpful when I start re-archiving as I come up on the 10-year storage cyle that's recommended. I'll probably worry about it when the index files get too big for one CD.

John

Subject: RE: storage of cds
From: Gene
Date: 21 Jan 08 - 10:41 AM

A few years ago many (including me) were using the Press On Labels

Didn't take long to find out they tended to WARP over time, making certain portions of the CD unreadable. I recovered data from many
by clamping between two other unuseable cds and placing in freezer
for 10-15 minutes...long enough to recover the data before the cds
re-warped...from the heat of the lazer.

A local pal of mine had one STOMPED label come unglued and messed up his CD Writer...

Nowadays CD and DVD blanks are very inexpensive...so BURN EXTRA
copies of those you treasure most.

Subject: RE: storage of cds
From: JohnInKansas
Date: 21 Jan 08 - 08:55 PM

Labels on CDs are a potential problem. Many of them that don't warp the CD tend to "stretch" and raise bubbles in the label that can snag in the player/reader¹. I've seen no indication that the better quality labels cause deterioration of the disks themselves, although I can't rule out the possibility.

¹ Many pressure sensitive labels run right out to the edge of the CD, and quite a few common "music CD players" - especially portables and vehicle "dashboard" units - apply a "damper" to minimize bouncing around while the CD plays. The damper is often just a small felt pad that rubs on the outer face of the disk. Any bubbles, buckles, or frayed edges on the label may make the disk "unplayable" in a player of that kind. A "proper" label for disks to be used in this kind of player would leave a bare rim about a quarter inch wide, but I haven't found any like this.

For archiving, a common recommendation is that no labels should be used, with each unmarked CD in a case with an acid-free label on the case. This could theoretically be a manageable method for the extremely anal-retentive administrator where no one but the person in charge ever has access to the archive, but for most people the CD must be marked in some way.

A felt-tip marker and a simple disk number may be sufficient for data CDs and maybe for archived music CDs - if you keep a complete and accurate index of any information you need about what's on them. You may still want paste-on labels for your "playable" music CDs, but those can be replaced as needed from an archive CD that doesn't really need a detailed label.

If you want to be extra cautious, a felt tip "number" can be placed in the hub area, or for a "less than full" CD, around the outer rim. (CDs play from the inside outward. With careful examination in a good light, you usually can tell where the "recorded part" ends on the disk so that the markings can be made where there's no data.)

For data archives, a list of the files on each CD is, for my purposes, sufficient, so after the CD is burned I try to immediately, at a command prompt, go to the folder where I keep the index files. I would see a prompt like C:\CDIndex>

From there, with E:\ as the drive containing the CD, I'd run:

DIR E:\*.* /s >filename.txt

This puts a text file containing a list of the files on that CD in my index folder.

For the filename, I'd use the "CD Number"+a brief description of the kind of data, like "1048_emails_080120.txt" (for emails archived yesterday).

With ALL of the CD index files in one folder, Windows Explorer can fairly quickly find a particular file name, and the number that's part of the CD index file name tells me which CD to pull out.

Text index files for 250 CDs would likely run less than 30 MB, which is pretty small for a CD, so if you feel like it you can add the whole index folder to an occasional CD, along with whatever else you're burning, and have an updated archive of the index as it grows.

Different methods probably will be needed for backups that contain more music/video than data, so each archivist will need to do some serious thinking about "what's sufficient" vs "what's possible."

"Who's gonna care enough to look at it when I'm gone" may also enter the archivist's planning too.

John

Subject: RE: storage of cds
From: Mrrzy
Date: 22 Jan 08 - 07:11 PM

I had a friend who was a DJ, and his house burned down and melted all his vinyl but his CDs were fine... this was in the '80s, maybe early 90's... so I think the high temp must be pretty high.

Subject: RE: storage of cds
From: JohnInKansas
Date: 22 Jan 08 - 07:54 PM

In the 80s - 90s his CDs probably were commercial "pressed" disks, with the data imprinted as molded mechanical pits. The most likely disk material, probably polycarbonate(?), would not melt at as low a temperature as the vinyl used in many LPs of the same period, but would warp at only slightly higher temperatures.

For CDs made as home recordings, the data is in a "photosensitive" chemical layer that isn't likely to survive much exposure to any "energetically active environment."

I've seen one instance where a "house fire" left water standing in a glass on the table three feet below a common 60W light bulb in which the glass envelope of the bulb was melted and the "bulb" sagged to about 9" long. (The fire inspector pointed out that the bulb looked more like some bizarre sex toy than like a light bulb.) It's very difficult in such cases, especially for "house fires," to support any argument that everything in the fire was exposed to the same - or even to similar - temperatures.

Any "warm" temperature uncomfortable for you to be in for long periods is not a good place to keep either vinyl or CD recordings. Temperatures that don't produce obvious damage during short exposures will still degrade or destroy the data on CDs if the same conditions persist over longer times.

John

Subject: RE: storage of cds
From: Nerd
Date: 22 Jan 08 - 09:44 PM

Did I miss something? Didn't Captain Birdseye ask about CDs, not CDRs or CDRWs? Wouldn't this mean, in JohninKansas's words, commercial "pressed" disks, with the data imprinted as molded mechanical pits?

Captain? Which did you mean?

Subject: RE: storage of cds
From: The Sandman
Date: 23 Jan 08 - 05:05 AM

commercial pressed discs.http://www.dickmiles.com