I love physical media, you love physical media. Physical media is awesome, and generally just better than digital streaming or downloads, if a little bit less convenient.
However, being physical items and not digital files backed up over numerous computers in a data center, physical media does have the unique drawback of degradation. While CDs and DVDs aren’t nearly as fragile as vinyl records or cassettes, if you don’t take care of them (or even sometimes when you do!) they might be heading towards their end right as we speak.
The Illusion of Permanence
Everything is relative, and compared to vinyl records and cassette tapes, CDs are much more durable. I remember demos from the early days when someone would drill a 2mm hole through a CD, and it would still play. Of course, this was a bit of a trick, since the CD would still audibly skip, but these discs were marketed as being tough and long-lived.
In theory, they absolutely are long-lived. A factory-pressed CD (not a writable disc) should last longer than the average human lifespan, assuming it’s kept under ideal conditions. However, we don’t live in ideal conditions, so you can’t assume your CDs will just be around for the next 100 years without any input from you!
How Optical Discs Actually Store Data
To understand where the weaknesses in these optical discs lie, we need to take a second and explain how they work. Each disc consists of layers: a clear polycarbonate substrate, a thin reflective layer (usually aluminum or gold), and a protective lacquer coating. The data is stored as a series of microscopic “pits” and “lands” that a laser reads by measuring how light reflects off those surfaces. The pits and lands represent binary code.
Recordable discs swap out the metal layer for a special dye that changes state with the application of heat from a laser. These discs can last many years, but are orders of magnitude less stable than factory-pressed discs.
The Silent Killers: Disc Rot and Degradation
The biggest cause of disc errors is scratches. If the outer layer is scratched, that can prevent the laser from reading the data in the metal layer. Special disc buffing tools can sometimes remove these scratches, but there’s only so much surface you can remove before the CD or DVD is destroyed. If a scratch is deep enough to hit the metal layer where the data actually lives, that data is destroyed.
However, even if you keep your discs completely scratch-free, there are other maladies that can affect them. Disc rot is the one you’re most likely to hear about. This happens when the metal layer of the disc slowly oxidizes, rendering the surface unreadable by the laser. This isn’t supposed to happen, because the disc is sealed in plastic and lacquer. However, damage to the disc, such as chipped edges, can expose the metal layer to the outside atmosphere. In some cases, this could be thanks to a defect in the manufacturing process, but the issue would only become apparent years later.
The plastic layers can also delaminate or cloud up as adhesives break down. Heat, humidity, and UV exposure speed up the process. Writable discs have a different issue, where the dye simply degrades with age. It can fade, shift color, or chemically react with the bonding agents holding the disc together.
How Long Do They Really Last?
Predicting how long physical media will last is hard for many reasons. For one thing, not enough time has actually passed to know whether a disc that claims a 100 or even 1000-year lifespan will live up to it. Conveniently, everyone involved in making that claim will be pushing up daisies by the time the expiration date rolls by.
What we can observe is that lifespan varies from disc to disc, and so there are discs that are perfectly fine after 40+ years, and some that died in less than 10. Anecdotally, many of my parents’ CDs from the ’90s and late ’80s are still fine, and disc attrition there has been largely down to accidents or poor handling. I’ve burned hundreds, if not thousands, of writable CDs and DVDs in my life, and assuming they survived the first few months, they’ve all been thrown away because I didn’t need them anymore, not because they failed.
High heat and humidity are the main killers of basically all physical media, so if you handle your discs properly and store them in a cool, dry place, chances are they’ll outlast your need for them, if not outlast you.
Saving Your Data Before It’s Too Late
That said, in reality, I think you should check your discs for signs of oxidation or discoloration at least once a year. The good news is that, unlike vinyl records and cassettes, it’s simple and convenient to make backups of your optical media with zero loss of quality. Hard drive storage is cheap these days, and investing in, for example, a large external drive, will let you make backups of your discs in case something goes wrong with them. If you use the backups to consume your content, it also reduces the wear on your physical media, so that’s a win-win in my book.
While I consider CDs, DVDs, and Blu-ray discs the least vulnerable of physical media, that doesn’t make them invulnerable, and it’s not a huge task to check in on them now and then to ensure your collection remains playable.
- Storage Capacity
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2TB
- Compatible Devices
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USB
- Brand
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LaCie
