Data rot is something that has somehow lost the limelight for quite some time now.

Previously, it was most famous as laser-rot. Laser-rot was a phenomenon related to Laser Disc (LD) pressings.

In general terms, data rot is a recording of any kind that goes bad. 

Think about the last time you recorded some music you bought from an online store? You downloaded the tunes, copied those to a disc and took it in the car with you. You were really happy because not only were they the songs you wanted, they were on a disc! That means they're yours forever... ummm... doesn't it?

When most people record a new disc, they're all pretty convinced that the media we're using is stable and reliable. After all, it works now so why won't it work in the future?

When it comes to recordable media, the real life expectancy is two to five years under normal circumstances.

Most people feel that they've recorded it to a 'CD' but they're not thinking one step ahead. It's a recordable CD.

The data carrier - the disc - is a CD but the technology behind the recordable part is flawed. 

Let's look into how recordable media works. 

Just like a replicated CD or a DVD as you would buy music or a movie on, recordable optical media is reliant on a polycarbonate substrate. That part is pretty reliable. It's a plastic - a very special kind of optical grade plastic - that is resistant to strong UV, heat, infrared and whole lot more. It's not likely to change very much unless it somehow is exposed to temperatures over 110^oC  (around 230^oF) for a few hours.

Generally, the part of recordable media that fails is the dye layer. 

The dye layer is just that - a dye. It's a photosensitive dye. It is most sensitive in a certain part of the light spectrum. Other light frequencies have a measurable effect, but it's far less than that of the recording laser for a CD-R or DVD-R.

It's kinda like old-fashioned black and white film or print paper - you can unpack it in a dark room with a safelight and nothing bad will happen. Unpack it in daylight and it's worthless. The same principle applies to recordable CD and DVD. BD-R too!

That effect of other light frequencies outside the correct ones is cumulative. In other words, you can let the disc sit outdoors on a sunny day for a few hours and it will still play nicely. If you leave it outdoors for a week then it might not do so well. A month? Maybe. A few months? Wow! You just got a shiny thing that doesn't do anything. Woohoo! A new coaster! Cumulative broad-spectrum light degradation. 

The failure of the disc isn't just about the dye layer's inability to deal with broad-spectrum light. It's also about heat, cold, combinations of the two and so much more. 

When recordable media is exposed to heat, the dye layer may begin to have a chemical reaction.

That reaction may cause a release of gas. However, the gas has nowhere to go. After all, it is sealed in under a layer of metal (the reflective layer) and a layer of topcoat (a lacquer which is spin-coated onto the reflective layer to protect it from oxidation and physical damage).

Result? The reflective, shiny layer has a bubble or two under it and the disc isn't readable. Even if you manage to press the bubble down pretty flat or try to pop it, then there will be defects in what should be a perfectly flat and smooth mirror surface. You just got a disc which won't play. 

Exposed to severe cold? The metallised, shiny layer may contract and split. We are however talking Canada cold here. Beijing cold. Michigan cold. Snowy Mountains cold. Glasgow on a really bad day. Skye on a really good day (sorry, McKinnon!). Antarctic summer. Really nasty -15^oC or worse cold. Not probable in Sydney, Australia - but hey - we love to show off our moderate climate even in the middle of a technical article. 

Similarly, taking recorded media from your warm car to outdoors so that you can bring it into your warm house may be enough to shock it into failure. As little as 10^oC thermal differential for a ten minutes is enough to change the quality of an existing recording and certainly enough to cause issues with recording to fresh media in all except the best recordable discs. 

It's the same for CD-R and DVD-R. 

While these are extreme examples of how data rot occurs, it's the same in your office. 

Certain handling of optical media can render its life much shorter than the manufacturer intended. Often, this kind of handling is in error. However, the data's value is still important for your firm.

Keep the media cool and dry. Please don't touch the data surface (the side that faces down when you put it in a player) and don't use it for a frisbee to haze the new guy's head. 

Choose top grade media, take care of it and it's going to do the best things for you. 

Cheers Red Circle Media - Technical Section.