Foetusized's Page about CD Rot Web foetusized.org

CD Rot (aka Disc Bronzing)

what it is and what to do about it

	My copy of Quilombo by Steroid Maximus, scanned in 1998, showing the classic symptoms of disc rot. The detail at left shows the bronzing around the edge. This could be seen better on a disc without a label, but it was the example I had on hand at the time.
	Same CD about five and a half years later. The music still plays clearly all the way through, but it has gotten darker around the edge. I plan on sending it to PDO for replacement soon.
This is the oddest looking example of CD rot that I have, and is not a typical example. This CD single of "China Doll" by Julian Cope came in a cardboard sleeve, and the lacquer reacted oddly with the unbleached cardboard causing this spotted discoloration. This disc is starting to show some background noise and needs to be replaced. Note the text (in negative from the top side) "Made in U.K. by PDO".

CD rot, also called CD bronzing, is a real but rare problem. These discs have a problem with the aluminum in the disc corroding due to a certain lacquer used in the label, which reacted to chemicals in the disc booklet. These discs were made by Polydor & Du Pont Optical UK Ltd. (PDO), and were generally UK pressings (sold elsewhere only as imports). They were made from the late 80's to the early 90's, but not all discs made by PDO in that time frame exhibit this problem.

CDs with bronzing or rot can be identified visually. The darkening caused by the corrosion starts at the outside edge and progresses inward. Eventually the corrosion will cause sound problems not unlike LP surface noise, which will be worse at the end of the disc (CDs play from the inside to the outside). This is a progressive problem -- once started the disc will continue to deteriorate. PDO discs are distinctive in that they generally say "Made in U.K." or "Made in U.K. by PDO" in the center ring, and have a narrow center clear ring (not the common wider clear ring, and not the full aluminum disc that Polydor makes at their German & US plants).

2007 Update After 15 years of replacing rotting CDs, the current owners of the PDO plant quit doing so, as of November 2006. As a result, instead of attempting to get replacements from them, you should contact the record label that released the CD if you have any discs that need replacing for this problem. If the label is no longer is business (as is the case for a couple of CDs I own that are starting to rot, but had not yet contacted PDO for replacement), then you have been hosed (as I have been). My rotting CDs still play fine as of now, so I have made lossless copies of the music on them onto my computer, just in case.

2004 Update In May of this year, the Associated Press ran a story about the durability of optical media, which was headlined CDs, DVDs not so immortal after all on the CNN and USA Today web sites. I discovered the article after I saw a big spike in traffic to this page, particularly from CNN, the day the article ran. Unfortunately, some of the people the AP reporter talked to for the article don't understand the difference between CD rot (the CD bronzing discussed above, caused by problems with materials used in manufacturing) and the damage to optical media due to mishandling or improper storage. One expert they interviewed, Jerry Hartke of Media Sciences Inc., did get it right. The quotes from him are the best part of the article. The other expert talks about CD-Rs, which is a whole other subject than the manufactured discs everyone else in the article is talking about. Unfortunately, the "Fact Box 'CD Rot' Dos" sidebar that CNN used has nothing to do with CD rot, but it does contain good rules for CD and DVD handling. Mark Irons, who is interviewed in the last few paragraphs, has long had a page about CD rot that, up until now, I've chosen not to link to from my site, because he gets it wrong in my view. His CDs are not damaged due to CD rot, but because of storage problems. According to his site: "In the winter, they [CDs] were in the same room as the wood stove. Since we only fired it up at night, the temperature could range from 30F to 70F in two or three hours. The CDs were less than eight feet away." His CDs are coming apart because they were subjected to such extremes in temperature over such a short time. The pin-prick hole damage suffered by Dan Koster (the other consumer interviewed) could have been caused by mishandling leading to damage to the top layers of the discs. I've also seen a few CDs I bought new in the 1980s (usually manufactured by WEA) come out of the jewel case the first time with such pin-prick holes, but the ones I own have never gotten any worse nor ever had any problems with playback. In short, I still see "CD rot" as a term for a more specific form of CD deterioration, and not for damage to CDs caused by not taking care of them. Personally, with the exception of five or six discolored CDs made by PDO, and one single WEA manufactured CD I purchased used which has experienced similar issues, all of my thousands of well-cared-for manufactured (not CD-R) compact discs are continuing to work fine.

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