Like many people, I back up my raw files to CD for archiving. Typically, I'll make two copies of everything; one copy goes into a small fire-proof box and the other into a drawer for when it's needed. I've known about the possible instability of CDs and the danger of losing data for a while, and it's been an item on my "one-of-those-things-to-do-sometime" list for a while. The 3 Nov '03 edition of The Langa List (now defunct) was in my mailbox this morning, and the first item was on this topic. Fred was following up on a story that appeared in the Dutch magazine PC-Active, which suggested that CDs could become unusable in less than two years (if you can read Dutch, here's a link to the article). Well, I bought my first digicam - a Digital Ixus - in Dec '99 and my first DSLR - a D30 - in March '01, so I figured I'd best take a look at things.
Update 5 Feb '04: The US National Institute for Standards and Technology has published a report, Care and Handling of CDs and DVDs, which gives some additional guidelines that I've added to my original list. The additions are mainly with respect to handling, in particular, storing them upright, like books.
Do's and Don'ts
First some guidelines on the use and handling of CDs:
• Do handle the disc by the outer edge or centre hole
• Do use a felt-tip pen intended for use with CDs, otherwise use a non-solvent-based felt-tip pen on the clear plastic centre. Otherwise you may scratch the disc or the ink may react badly with the disc.
• Do put CDs in sleeves or on the spindle that often comes with them, and store them in a cool, dark and dry space and store them upright, book-fashion.
• Do wipe from the hub to the edge, not in a circular direction, if you must clean a CD - scratches across the have less effect than those that go around.
• Do use CD/DVD cleaning detergent, isopropyl alcohol or methanol to clean stubborn marks.
• Do make duplicate copies.
• Don't use sticky labels on the CD - the glue may cause deterioration.
• Don't use a ballpoint pen - danger of scratching.
• Don't leave CDs lying around near hot equipment or in direct sunlight or in damp conditions. This can affect the dye used in the CDs and in extreme conditions bacteria can attack the discs.
• Don't bend CDs.
• Don't rub them with anything abrasive.
• Don't open the package until you are ready to use the disc.
Checking your CDs
One way, of course, would be to copy the contents of the CD back onto your hard disk, which can be a slow process. However, there's a free utility, Opti Drive Control (originally CD Speed 2000), available from CD Speed. (This is part of the same mob that produces Nero, the CD/DVD writing software package; CD Speed comes as part of the Nero Suite).
This was the worst CD I tested, but having examined all 11 of my 2001 CDs (around 3,000 pictures), six contained one or more damaged sectors. None had any unreadable sectors (the last one on every disk was red as in this screenshot, so I'm assuming that's not a problem indication), but not a very comforting statistic.
I've copied all 11 disks onto the hard disk and I'm going to see whether Nero does a better job of creating "undamaged" disks that my existing software (which came bundled with my DVD-RAM drive).
3 August 2009, originally published November 2003