Re: Life time of a DVD (and various CDs)

From: Phred <ppnerkDELETETHIS_at_yahoo.com>
Date: Tue, 02 Dec 2003 15:52:56 GMT

In article <bqgd92$21hhae$1_at_ID-76636.news.uni-berlin.de>, "Ken Taylor" <ken123_at_xtra.co.nz> wrote:
>"Uncle Bully" <wakeupcall_at_optushome.com.au.REMOVE> wrote in message
>news:3fcba79e$0$20418$afc38c87_at_news.optusnet.com.au...
>>
>> > Does the life time of a DVD change with the disc use or more with the
>> > way the DVD are kept.
>>
>> Yes. For example, I used to keep mine in the fireplace and I found they
>> didn't work the next time I used them. Keeping them on the floor of the
>> garage wasn't a good idea either. In a cupboard or on a shelf is probably
>> a better idea...
>>
>Aside from high temperatures and rough handling, which you covered, albeit a
>tad tongue-in-cheek, high humidity is also a killer.

Yeah. I hadn't realised until I read some detailed info recently[1] that the polycarbonate layer is a "soft" plastic that will absorb fluids such as water. I gather that the reflective layer in "pressed" DVDs and CDs is aluminium, and that can go dull pretty quickly in the presence of oxygen -- and moisture will provide a conduit for oxygen.

Surprisingly, the stuff I saw suggested that the pressed forms may have a shorter life than the CDRs etc., largely due to the use of silver or gold reflective layers in the latter.

The reflective layer is aluminium in the various forms of RW disks too, but with these the phase-change data layer is not as stable as the dye layer in the CDRs etc., so it's assumed the data will be lost before the aluminium rots anyway. Thus RW and RAM disks are not considered suitable for archival storage.

Another surprising thing I learnt from all this is that these disks should be stored *vertically* and NOT flat. It seems long term flat storage may lead to sufficient physical distortion of the media to make it unreadable.

[1] National Institute of Standards and Technology, Special Publication 500-252, "Care and Handling for the Preservation of CDs and DVDs - A Guide for Librarians and Archivists". <http://www.itl.nist.gov/div895/carefordisc/disc_care/>

Cheers, Phred.

-- 
ppnerkDELETE_at_THISyahoo.com.INVALID

Received on Tue Dec 02 2003 - 07:52:56 PST