Disc rot

CD rot (or DVD rot) is a common phrase describing the tendency of CD or DVD disks to become unreadeable within a few years of manufacture. The causes of this effect vary from oxidation of the reflective layer to ultra-violet light damage and debonding of the adhesive used to stick the layers of the disc together. Since much use is made of CDs and DVDs as backup media, the potential impact of data loss is great.

CD rot versus DVD rot

Tests conducted in artificial environments indicate that the onset of DVD rot occurs more quickly than that of CD rot. The reason for this has still not been determined.

DVD Rot

DVD rot has been reported to occasionally be found on Early Pre 1999 DVD presses^{[citation needed]}.

On reported DVD Laser Rot cases, the Rot is noticeable when there is a chapter change. Usually it shows up as Pixelisation.

CD Rot

Laser Rot reportedly was a frequently occurring problem in many early compact discs (CD) production runs. On CDs, the rot becomes visually noticeable in two ways:

When the CD is held up to a strong light, light shines through several pin-prick sized holes. This is especially noticeable in older CDs that have a label of black text and a silver finish.
Discoloration of the disc, which looks like a coffee stain on the disc.

In audio CDs, the rot leads to decreased audio quality, chatter, scrambled audio, and static.

Means of circumventing CD rot

As a result of CD rot, many data archive experts say that data is safer on a live hard disk,^{[citation needed]} and even more so in redundant hard disk systems such as a RAID. A simple way of circumventing CD rot is to make back up copies of critical information, either to another CD or to a hard disk. One method found to slow down the advent of CD rot is to store CDs in a refrigerator (or even in a freezer) in a sealed bag to prevent icing. This will slow down the chemical reaction which causes the CD to rot.^{[citation needed]}

Evidence

According to a BBC report[1], music CDs had begun to deteriorate and become unplayable by the 1990s. According to CD manufacturer PDO (Philips-Du Pont Optical), the affected discs had been made in the late 1980s and had used a silver coating on its discs instead of the standard gold.

Philips communication manager Jeannet Harpe has declared CD rot to be an isolated problem affecting only an "absolute minority" of cases. PDO has offered to replace any discs thus affected if supplied with the defective disk and proof of purchase.

External links

BBC article
Mac Observer article
"CD Bronzing" article, with PDO replacement information, at Classical.net - How a manufacturing problem can cause disk quality degradation.
"Using CDs for Data Storage" article, with extensive footnoting. Much of the information contained here contradicts central tenets in this wiki entry.