Documentary heritage: fungal deterioration in Compact Discs | Hacker News Reader

Documentary heritage: fungal deterioration in Compact Discs

heritagesciencejournal.springeropen.com

52 pointsHooke32 comments

I have a DVD bought off of ebay. It's probably 20 years old, but never opened. It was a soccer-teaching video for kids that my girlfriend bought because she starred in it as a kid.

When we opened the package, we found that there are ~100 raised white spots on the surface of the disc, about 1mm diameter. They don't wipe off easily. We haven't been able to get the disc to play. I would love to know of a good way to clean these, and also what they are -- fungus hadn't occurred to me before but seems possible.

Try using a piece of cloth, some water, and a little bit of dish washing soap

Yeah, from what I've read from optical disc enthusiasts[1] isopropyl or plain dish soap with a cloth rag is suitable for cleaning. Anything that can cause abrasion like paper towels are best avoided.

[1] http://www.digitalfaq.com/forum/media/12002-maintenance-opti...

Be careful with isopropyl. I've seen 70% or 91% poured over the print side of a movie DVD, causing it causing the printing to slough right off.

For what is worth I have successfully dealt with scratched CDs by applying a cream that I found to be almost the same refractive index as the plastic of the CD.

When I was young, I had a few scratched PS2 games that wouldn't play. Some advice on the internet was to put toothpaste on the CD, gently rub it in small circular motions around the CD with a paper towel, then rinse it off. Perhaps I'm misremembering, but I remember being surprised it worked for most of them.

It might've been specific to PS2 games and whatever material they were made of and/or how they were pressed, so I wouldn't recommend it as general advice. This thread just reminded me of it.

Toothpaste is a mild abrasive, if the scratches weren't deep it removed them entirely.

I still feel that a fluid that can fill the scratches and cause them to basically disappear is much better.

If the CD is damaged the goal should really be to read the data once, then throw it away. So I think it is fine that the filling/oil/grease is one time only because I don't need it to work more than once.

With toothpaste there are risks. There is the risk that the scratches are deeper. Not only you will not be able to polish it out, you can get toothpaste particles in there permanently.

In any case, applying oil is just so much easier -- you only need to wipe the CD with it and then wipe the excess thoroughly.

I've heard the same advice for treating light damage on an LCD screen. The deciding factor between using either method should indeed be the depth of the scratch (and how well you can estimate it).

Sometimes helmet grease works, too.

Article is about CD-Rs, afaik those used organic dye. DVD you bought sounds like pressed one = no organic materials. Whats more DVDs are build in a way where the data surface is sandwiched between two sealed polycarbonate platters.

It might help a lot if you could post a picture of it.

Update: rubbed a bit harder with some IPA and they came right off. Now I just have to find a working dvd drive. Edit: I did, and the disc works fine! Imaged and ripped it.

What is IPA? Isopropyl alcohol?

Yes. Sorry about that; got in the habit of using the abbreviation at work where we clean a lot of 3D-printed parts with it.

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.

[Account created by mistake]

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?

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.

I think if you vacuum sealed the disks it would help prevent the issue.

You would think this, but I don’t think it’s true. Effectively sealed optical discs still get fungal growths. I think the fungal spores are already on or in the disc

I can't be the only one amazed that fungi is biodegrading these materials. Fungus really is an amazing organism we don't know enough about

I have never liked the CD/DVD media. As much as its durability is alleged, I have not experienced it. They are very sensitive to scratching and must be spotlessly clean to work. In the hands of children, I always had better luck with VHS tapes.

They don't have to be spotless. Audio CDs at least also play when scratched and dirty-ish. I don't recommend it, because the dirt can fall off and accumulate inside the player, but I've had very few problems. I got my first in '84 or '85, and all but two of 500+ still can be played back. I've never had a problem with a DVD, but they are considerably newer.

Audio CDs are still able to play back with significant bit errors (CD players just interpolate over the unreadable parts). It’s different for CD-ROMs and data CD-Rs.

And all your well kept WiiU Blu-ray Discs will spontaneously stop working, despite proper storage. Whatever process they used didn’t work.

CD-Rs always smelled vaguely like celery to me, I wonder if this has something to do with it?

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