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Guide to Digital Preservation from NIST
Little Hamster writes "The scientists working on the Digital Preservation Program at the National Institute of Standards and Technology (NIST) has released an excellent 50 page guide on care and handling of CDs and DVDs for long term storage. It talks about the effects of light, moisture, radiation, scratches, marking, adhesive labels, and even playback on the discs. For those slashdotters who is not familiar with the physical made up of these optical discs, there is a very nice chapter explaining all the background. And if you only want to know how to care for your precious data, there is a one page summary. And yes, they agreed that glued-on labels are harmful."
The Library of Congress has a guide right here!
1, 1, 2, 3, 5, 8, 13, 21 -- Mathematics is the Language of Nature.
from the 50-page pdf:
Physical mishandling of the disc is usually the cause of polycarbonate*
layer damage. The polycarbonate may also flex or bend if
stored for a long period of time in a nonvertical position.
and
Long-term horizontal storage, particularly in a
heated environment, can cause the disc to become permanently
bowed. While the data may still be intact, the disc may not operate
properly in the drive or permit the laser to follow the track.
*3.1 Polycarbonate (Plastic) Substrate Layer
The polycarbonate substrate makes up most of the disc, including
the area that is read by the laser (opposite the label side on CDs). It
is present on both sides of a DVD, even a "single-sided" disc with a
label on one side. This substrate provides the disc depth necessary
to maintain laser focus on the metal and data layers. It also gives the
disc enough strength to remain flat. Anything in or on the polycarbonate
layer that interferes with the ability of the laser to focus on
the data layer will result in the misreading of data. Accordingly, fingerprints,
smudges, or scratches, as well as such substances as dirt,
dust, solvents, and excessive moisture (which polycarbonate will
absorb), can interfere with the ability of the laser to read the data.
Contact of any foreign material with the polycarbonate substrate
layer should be avoided.
Yes, Sharpies are solvent-based. Look for water-based inks.
Media capacity follows the standard technological growth curve (aka Moore's Law) so that it is both convenient and practical to move your entire library every few years.
Thus my MP3 collection has migrated over time from Jaz cassettes to CDR to large hard disk to DVD.
Apart from the practical aspects of finding a reader for old media, the sheer space taken by old media (e.g. my twenty-odd Jaz cartridges) makes it useful to move regularly.
My MP3 collection, freshly re-created from my original CD collection, fits onto ten data DVDs while it would require about 70 CDRs.
Doing this, while also keeping multiple archives on hard disk (CVS mainly) means I have no problem accessing projects that I worked on 15-20 years ago. No way would I have confidence in diskettes or backup tapes from the same period.
Though I do have a 50cm-wide 150Mb removable Wang disk that has some interesting stuff on it if anyone has an old Wang VS lying around.
Ceci n'est pas une signature
Putting them in a ziplock bag won't do all that much to protect against humidity. You want to put them in a sealed (with vaccum grease) glass or plastic vessel with desiccant, a water-absorbing material. That will keep your stuff cool and dry. They make cabinets that you can just put in your refrigerator.
Not only am I a scientist, I play one on TV
The actually "guide" to care for your DVDs and CDs isn't 50 pages... it's about 2 pages of "do"s and "don't"s. The rest is just technical mumbojumo with the TOC, definition reference, bibliograpy, and other legal stuff at the beginning.
"WOAH 50 PAGES!" Well... yea... but the important stuff is only on a few of them.
So if you plan on printing this out for easy reference... save yourself the extra 48 pages.
NIST tells us not to use anything solvent-based, and Sharpies are solvent-based markers. In fact, the Sharpie Materials Safety Data Sheet (pdf) tells us they contain 3 different solvents - a propanol, a butanol, and an alcohol. One Eric Teel of Jefferson public radio (in Oregon) wrote the manufacturer of Sharpies and they said there could be problems.
Damn, and I've got hundreds of CD-Rs written on with Sharpies. I hope they last till I get around to buying a DVD burner and transferring the data.