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Comment by jacquesm | Hacker News Reader

Aluminum based CD-R are a bad choice for this, if you want to have CDs that last long (or DVDs for that matter) you should use gold based ones, they last a lot longer than the aluminum ones. They are also quite a bit more expensive.

Look for 'Archival Grade' or something similar in the product name.

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AFAIK, there are no aluminum based CD-Rs, the silver-looking ones actually have silver or silver alloy reflective layer.

Not as far as I'm aware, it is a very pure aluminum layer. The real weak spot is the edge of the sandwich, especially if there is some form of thermal cycling, that can cause delamination to a degree that it will let a little bit of air in. Maybe I'm mixing up CD-R and CD-RW? The effect of corrosion on silver would be much the same as with Aluminum though, the silver would lose its reflective capabilities and that would show up as data corruption. I'd definitely still go with the gold version.

Aluminum is used for pressed (readonly) CDs.

You're right about the rest.

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Gold doesn't oxydize. AFAIK that is a problem that sometimes affects aluminium based discs, when the polycarbonate seal is defective.

If you want to be really sure of maximal shelf life, you'd use glass instead of polycarbonate as well - the manufacturing technology exists: https://www.theabsolutesound.com/articles/the-2000-cd-made-f...

But all of that is really not relevant at all for backups because the CD-R dyes will degrade long before the reflective layer. The shelf life of the reflective layer is an issue when talking about pressed discs.

Fascinating article that, it borders on the HiFi madness but does so in a way that it leaves some wiggle room for an actual effect. Pity he didn't take the time to do a 'diff' between two signals on a sampling memory scope. If there was a difference in the output that's where it would show up the clearest.

Yeah, the audiophile angle is... Strange. But my point was really that glass would last much longer than polycarbonate.

Because gold is incredibly non-reactive?

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