Please be aware that the linked article has been written by a pulp magazine computer journalist, i.e. someone who doesn't read technical literature and writes what they please. I'd better not go on, or I might say some really derogatory things about such people, such as the practise of writing reviews without ever setting eyes on a piece of hardware (not that I'm implying the author in question would do anything of the sort).
Here's the
original material on which his article is based. The 'Quick One-Page Reference' has been around for quite some time in one form or another and doesn't appear to have been based on the research. As others have pointed out, it's mostly the same list of conservative handling suggestions that applied to vinyl discs.
Please read the full publication instead.
And now, because I'm a terminal masochist, I'm going to critique the article.
So what is the likely life of your CD-R, CD-RW and DVD-RW disks today ... [NIST] has come to the conclusion that the scientific answer to all these questions is: "not very long". It seems to be implying that prayer sessions may be helpful to corporations with large libraries of important disk data.
What they really said: "An accelerated aging study at NIST estimated the life expectancy of one type of DVD-R for authoring disc to be 30 years if stored at 25°C (77°F) and 50% relative humidity ... Among the manufacturers that have done testing, there is consensus that, under recommended storage conditions, CD-R, DVD-R, and DVD+R discs should have a life expectancy of 100 to 200 years or more; CD-RW, DVD-RW, DVD+RW, and DVD-RAM discs should have a life expectancy of 25 years or more."
It says, for instance, that true gold coating is better than any of the silver-coated (aluminium, etc) disks, which is not exactly news.
NIST (about CD-R, DVD-R, DVD+R): "These discs use gold, silver, or a silver alloy for the reflective layer
instead of aluminum as in ROM discs ... Silver is more reflective and cheaper than gold but is susceptible to corrosion if exposed to sulfur dioxide ... Manufacturers use various silver alloys to help inhibit silver corrosion, and most R discs available today use a silver alloy reflective layer ... With proper storage, these discs will outlast the technology."
CD-R is clearly the most reliable disk recording system because it has a more robust recording layer and greater tolerance for defects (inversely proportional to data density). Surprisingly, the NIST hasn't damned DVD-R as much as I expected, which suggests that DVD's advanced error-correction systems really work, at least in the short term.
Greater tolerance for defects? WTF? CD-R uses the same error-correction as other CDs. They said nothing about data density - in fact, they mentioned repeatedly how DVD's physical design makes them more robust than CDs!
NIST says disks should be stored upright, since the weight is then carried on the non-read outer edge or inner spindle hole, rather than on dust grains on the reading surface.
The bit about dust grains is complete fiction, i.e. he made it up. Firstly, remember that the reading surface is actually
underneath, where it's difficult for dust to accumulate. Secondly, every jewel or DVD case I've ever seen has a mount that suspends the disc by its hub. As NISC says, "Cases are designed to keep surfaces of the disc from contact with the inside of the case."
They were actually referring to
long-term storage, defined as "years", and their concern was that the disc might warp, "particularly in a heated environment". Remember the vinyl record connection?
Disks need to be kept away from circulating air to reduce corrosion and evaporation of the plasticisers.
Ummm, nope, they didn't say that either. Not even a hint, I'm afraid.
Storage should be cool, but not freezing (between 20 and 4 degrees C), and dark, since UV light has a destructive effect on some plastics and surface coatings.
Actually, they speculate that freezing may be beneficial, but note there is no research to determine this either way. In fact, they don't have research to back up the 4-20C range either, but deduce that lower temperatures should be better because higher temperatures clearly aren't.
They quote a variety of sources with different opinions on storage environments; it's worth noting that two of them allow temperatures as high as 50C. My own speculation is that like most things, you can probably tolerate higher temperatures if the humidity is low - check your wet bulb readings. The publication is more concerned with temperature and humidity gradients, which makes sense.
NIST says, "... degradation of the polycarbonate substrate (plastic) ... would become noticeable only after several decades of exposure to daily storage facility lighting or sunlight through windows."
UV can theoretically degrade the dye in CD-R, but manufacturers go to some pains to retard this, eg Super Azo. NIST says, "The most likely cause of damage to R discs from direct sunlight is by heat buildup in the disc affecting the dye. Much of the ultraviolet range of sunlight can be filtered (or absorbed) by glass, e.g., the glass of a window. However, the lower light frequency (infrared) range will pass through a window and generate heat in the disc."
The NIST condemns the practice of using adhesive labels on the disk surface because glue solvents penetrate the thin lacquer top-coat and damage the reflective layer directly beneath.
NIST did mention that, "The adhesive in some
earlier labels has also been known to react with the lacquer surface." But with current products, their concern was, "The label could delaminate over time and interfere with disc drive operation ... manufacturers advise against using adhesive labels because they can create unbalanced disc spin, resulting in premature wear of the drive." However, they also said, "Adhesive labels may be well suited for short-term disc usage (less than five years), and can even add a layer of protection from scratches and other potentially harmful contact."
Even worse is writing on the disk with a solvent-based felt-tip marker pen.
I can't really blame the journo for this one. The publication does go on about marker pens, but just like the last time I looked into this, they admit, "there are no explicit lab test results to show what effect solvents in markers have on different CDs or DVDs, particularly over the long term."
Personally, I am happy to continue with the trusty Sharpie, especially with the lacquered Verbatim "Crystal" discs I prefer. If I wanted a disc to last twenty years or more, I wouldn't be doing anything to it except writing on the hub as NIST suggests.
