this post was submitted on 02 Dec 2023
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CD-ROMs are read-only(-memory) & usually stamped plastic covered with mirror-ish surface (aluminum-somethings prob?).
CD-R have an (recordable) organic layer on top you can burn lil patterns into, once only.
CD-RW can be re-written several times.
But none of them really last long.
Many pressed CD-ROMs and audio CDs will likely last over 100 years if stored properly. However, the tolerances in the standard are high so lots of manufacturers use cheaper materials and processes than intended while still producing discs with the CD logo. It will take decades before we really know which were worse than others. The most likely point of failure is delamination, which will leak air between the layers and oxidize the aluminum coating in a process named laser rot after Laserdiscs, the earliest commercial optical disc system.
Anyway, the longetivity of (re)writable CDs is indeed usually below 20 years.
Yes, storage is very important in the long run.
And music industry indeed had some of the thiccest disks afaik.
No, it’s not about the thickness. Most of it is clear plastic anyway, the data layer is only in the top few dozen micrometers. Also, all CDs and later 12cm discs were 1 mm thick by spec.
Yes, I am talking about the top layer - some are def thiccer and more scratch resistant (I didn't mean thicket like you would notice looking at it from the side).
The recording layers of the CDDAs (1983-1987) had already vanished. So they lasted no longer than 40 years.
"SHM-CD"s would probably meet that 100 year mark but DVDs made them pointless by the time they were first released.