Storing Your Disks

A Long Healthy Life for Your CDs and DVDs
A Kodak data sheet entitled Permanence and Handling of CDs contains the advice "Long life for any information storage medium is always a combination of manufacturers' and users' responsibilities."

Never were truer words spoken. Manufacturers like Kodak, Sony and 3M produce high quality disks. But getting the longest life from those disks is the responsibility of the individual photographer.

A good rule of thumb is that if you're uncomfortable your disks will be too. So if you're storing your disks in an attic that reaches 110°F  in the summer and minus 10°F in the winter it's a good bet your disks will die young.

Repeated tests show that 95% of Kodak writable CDs will have a data lifetime of greater than 200 years if stored in the dark at 77°F (25°C) and 40% relative humidity. 

Stored in a "typical" office or home environment, the lifetime should be 100 years or more. 

-- from Permanence and Handling of CDs, a Kodak Publication.

50°F (10°C) to 77°F (25°C) and 20% to 50% relative humidity are the best storage conditions for your CDs and DVDs. Cycling temperatures and/or humidity between extremes will cause early failure of the disks as they expand and contract with each temperature change. 

You should avoid plastic or paper sleeves for long term storage. Over time they can adhere to the disk surface. Jewell cases provide the best protection for long term storage as they are a buffer against rapid temperature or humidity changes and provide protection from dust and light provided a cover sheet is in place.

How you label your disks can have an effect on their life as well. A ballpoint pen can cause compression of the polycarbonate substrate and the metallic reflecting layer in the area under the pen point. This can happen to both CD-ROMs, DVDs and writable CDs and DVDs, but the danger is more acute for writable disks. The adhesion between the dye and the other layers in a writable disk is weaker than the interlayer adhesion in a CD-ROM or DVD where no dye is needed.

User-applied labels of any kind can unbalance the disk and make it difficult for the player to read. Labels can peel in humid conditions further unbalancing the disk. Once a label is on the disk it is especially important that you do not to try and remove it. The act of peeling off a label creates a lever action that concentrates stress in a small area. Such stress can cause delamination, especially in a writable and re-writable disks. If it is necessary to write on the top side of a disk use a soft felt-tip marker, but with some solvent-based markers there may be a danger of the solvents migrating through the plastic into the protective lacquer. We've all had the experience of uncapping a marker with a strong solvent smell. Avoid such markers on your disks.

Disks may become dusty or dirty and may occasionally require a careful cleaning. Light dust or dirt may be safely brushed off with a nonabrasive tissue such as lens tissue. Always be gentle and wipe from the center toward the outside edge of the disc - never in a circle around the disk. If a scratch is created when cleaning, it will do the least damage cutting across a track, rather than along it. 

If more than dust removal is required, do not use solvents. Use a small amount of lens cleaner and a lens tissue, again working across the disk. 

Your disks will live longer when stored safely in a cabinet or file drawer. Sunlight is the enemy of any storage media. Keeping your CDs in a location where they are exposed daily to sunlight will drastically shorten their life.

Handling plays a part as well. When disks are handled repeatedly they'll get surface scratches and dings. Each scratch represents data that cannot be read. The disk drive attempts to reconstruct this data when you ask for a file and the format is amazingly resilient. But for important data and images it's a good idea to create a master copy and a working copy. The master is only used to create working copies and the working copies are used when you want access to the disk's contents. The good news is there is no degradation of the data when you copy a disk - whether it's your first copy or your 100th copy - all the more reason to work from a copy rather than a master.

So all that said how long will a disk really last? Data from Kodak shows that Kodak writable CDs will have a data lifetime of greater than 200 years if stored in the dark at 77°F (25°C), 40% relative humidity. Stored in an office or home environment, the lifetime should be 100 years or more. Tests by 3M show their writable CDs (CD-R) should last a similar 100 years when stored in "moderate storage conditions". So it appears that 100 years is a reasonable number for high quality CD-R disks. Their long life is mainly a function of the greater dark stability of the dye used in these disks compared to rewritable disks. You can expect similar performance from DVDs.

What about that 100 pack of cheapie disks you picked up at the office super store? Unfortunately you just don't know how long they'll last. But you can bet on one thing - they won't last anywhere near as long as high quality disks. This is one time when you get what you pay for.

There is a place for those cheapie disks though. If you're mailing shots from Little Ashley's birthday to your Uncle Floyd in Podunk use a cheap disk. They're also great for scratch disks. How about when you're out in the field shooting with your 10D? At the end of the day you can dump all your images to your laptop and burn them onto disk. This way you have two copies of all your images and you're covered if your laptop fails. Cheapie disks may not last 100 years, but they'll surely survive the length of your next photo trip.

But disk life is only part of the story. You must be able to access the discs' contents. A perfectly readable disk and no drive to read it with does you no good. So the survival of playback hardware devices and software formats is key. Migration of digital data from current storage mediums and software standards to future standards is essential.

Because migrating and upgrading requires effort and expense, there is a risk that it will be neglected. 

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