A DVD Is Not a Frisbee
By Walt Crawford
American Libraries Columnist
Senior analyst, Research Libraries Group
Column for September 2003
Do DVDs last? That all depends.
As I wrote in “Up to Speed on DVD” (AL, Sept. 1999, p. 71–74), “It could—and should—be your library’s next medium.” For most public and many academic libraries, that’s happened. In that article, I said DVDs don’t wear out from normal use. That’s true. Here’s the longer version:
“DVD offers a much more durable video storage medium than videocassettes. As with CD, there’s no physical contact between the playing head and the disc—and, as with CD, the data surface is protected by chemically inactive plastic.”
I ignored one critical detail: Library circulation turns out to be nothing like “normal use.” Many libraries have found DVDs to be shorter-lived than videocassettes—to the extent that a few librarians suggest going back to VHS. This column isn’t a mea culpa, but some clarifications are in order.
I saw a posting on Publib from a librarian saying the library was getting very few circulations from DVDs before they came back scratched, unplayable, even shattered. An off-the-record discussion with a library DVD distributor indicated that quite a few public libraries are complaining about relatively early DVD failure. The distributor opined that almost all of the problems related to patron abuse.
A quick survey on the Publib and Videolib lists yielded 22 responses. Half of those thought early DVD failure was a serious problem—but that included one who said it was only a problem for children’s DVDs, and another who indicated that “early failure” came after 100 or more circulations. If you can assume that libraries suffering heavy DVD failure were more likely to respond, it’s not a widespread problem—but I’m not willing to make that assumption.
Most failures come from scratches on the playing surface or broken and cracked hubs. Several libraries noted broken hubs as the primary cause of failure. Most wash and inspect DVDs before retiring them or rely on multiple patron reports.
Most libraries do take such palliative actions as washing “unusable” DVDs (13), liquid surface treatments (8), patron-education measures and abrasive treatments (for the DVDs, not the patrons!) (7 each), and optical paste repair kits (6). Eleven libraries use a variety of tools, including relatively expensive units from Azuradisc, DiscCheck, and RTI. Most respondents (13 of 22) found that DVDs didn’t last as long as CDs. More detail on the survey responses appears in the September 2003 Cites & Insights at cites.boisestate.edu.
Real problems, possible solutions
Two problems with DVDs make them more vulnerable than CDs:
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All DVDs are two-sided laminates, even if one side is blank. Instead of almost 1.2mm of polycarbonate protecting the information layer, a DVD has less than 0.6mm (less than one-fortieth of an inch). A dual-layer DVD has even less polycarbonate above the semitransparent layer. That means gouges and deep scratches are more likely to destroy a disc—and wide scratches are more likely to interfere with the focus of the laser beam.
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Most DVD packages (unlike CD jewel boxes) use press-to-release hub locks. If patrons pull a DVD the way most people do CDs, the lock places enormous strain on the disc’s hub—and eventually the disc’s hub breaks.
Distributors offer replacement cases that don’t use press-to-release hub locks, but only three survey respondents used them.
The biggest problem was one noted by several respondents: Patrons treat DVDs as though they were indestructible or free. They get stepped on, used as Frisbee replacements, tossed around, played with by kids who have no concern for their cost, and generally abused. There’s a good chance that thoughtful patrons will carefully wipe the DVD clean by wiping around the disc, which grinds dirt into a circumferential pattern that will make the disc unplayable.
Where do we go from here?
Some librarians spoke highly of cleaning and coating fluids and the more expensive cleaning machines. Optical paste can work in some cases. Abrasive treatment may work once or twice, but will eventually destroy the disc. User education isn’t easy, but it’s probably the most important step beyond simple washing.
Used with reasonable care, a disc should last longer than any DVD players will—50 to 200 years. DVD is still the visual medium of choice for the next decade or so, and many libraries do get more than enough use from the format to make it a cost-effective medium.
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