[WAY OFF-TOPIC] Holes in CD's - diyAudio
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Old 5th February 2002, 12:47 AM   #1
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Unhappy [WAY OFF-TOPIC] Holes in CD's

Hello,

I really wasn't sure where to go with this so I figured I'd start here. I've got a major problem. It seems several of my cd's have somehow developed microscopic holes that go through the layer of mylar(?) that contains the cd data. I have no clue how this happens but I can see through the very tiny holes when I hold the cd up to a light. This has happened to 6 or 7 of my cd's. How the heck does this happen?!?!? It's getting annoying!

Anyone else have the same probelm? Any suggestions would be appreciated...

Owen
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Old 6th February 2002, 05:42 PM   #2
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Default Describe this a little better..

You mean there are really small holes that go all the way through? or a deep pit that has somehow burned into the reflective layer? Size of small hole?

Sounds weird.
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Old 6th February 2002, 06:17 PM   #3
UrSv is offline UrSv  Sweden
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Holes in CDs?

I am sorry to say but I have seen that many times before. I used to work in a record store a few years back and some manufacturers or batches seemed to have that problem. In my opinion the holes in your CDs probably were there from day one but when you look at a CD with no bright light behind it (as there normally isn't) you don't see them. Holding the CD in front of bright light immediately reveils the holes however. I found CDs with just a few holes at around maybe .01 mm as well as CDs with 100 holes up to .25 mm (all numbers and sizes are rough estimates of course).

Check the CDs that you buy immediately and take them back to the shop if you find any holes is my sugeestion.

On some of my CDs there is a problem developing over time which is where the reflective layer slowly is truning red/yellow and loosing reflection.

/UrSv
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Old 6th February 2002, 08:39 PM   #4
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A long time ago I read a CD was specified to provide error correction across a 2.5mm gap. Almost immediately I was drilling holes into unwanted CD's I had lying around.
Results: My Phillips CD player could play over a 2.0mm hole with no audible glitch, but glitched when the hole was widened to 2.5mm
Not bad I thought...

Cheers, Adrian
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Old 6th February 2002, 11:27 PM   #5
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Unhappy Very small holes...

Hey all, thanks for the input.

The holes i am referring to are very small, the largest one looks to be about half a milimeter across, while the holes on the other cd's I have are less than that. The cd with the largest hole looks as if it had a very thin pin stuck through it because the plastic has been penetrated. The other cd's don't show this. They simply have holes in the reflective layer. And I know they were not there when I got the cd's because some of them I've had for a while and then all of a sudden they start to "loop" or skip a lot on a certain song. So, I pull them out and lo-and-behold, theres a hole right near where that track would be. Something else interesting is that all the cd's that this has happened to lack a label that completeley covers the top of the cd. In other words, they usually are cd's that have a little text printed on the 'non-data' side and you can see the reflective layer. maybe this has something to do with it? And often i've had these cd's for a while so I wouldn't be able to mail them back or whatever.

Any more ideas?

Thanks,

Owen
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Old 7th February 2002, 12:06 AM   #6
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I have heard that small holes in CD can be caused by microscopic fungi, moulds (I dont know the exact word) in tropical countries... one year after, or so, they are totally unreadable. It seems that remedy is not known. Special reflective layers (not aluminium) are not liable to this inconvenience.

Regards, P.Lacombe
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Old 7th February 2002, 01:01 AM   #7
Jason is offline Jason  Australia
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While we're talking about stuff way off topic and to do with holes, you might be amused to hear a story from my earlier years. Consider it garnish for the thread

I was living with my parents at the time (being about 5 years old), and was perched on a seat in the living room. On my right was a small table with telephone, and a bunch of loose pencils and pens. On my left was a potential pencil holder, given a bit of DIY nouse.

I spent the next hour pushing the pencils in and out of the the pencil holder, creating an array of pencil sized holes in said device-to-be. After I had finished, I inserted the few loose pencils and pens into aforementioned holes, finishing the job. How pretty, I thought. I then ran off to find my dad and show him what amazing DIY skills I had.

My dad had been off chatting with one of his friends, "Bab", and they both returned to see what I was making such a fuss about.

To my dads absolute embarrassment and Bab's horror, I had succeeded in turning the brand new and very expensive speakers Bab had just brought over to show off, into the worlds most expensive pair of pencil holders.
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Old 7th February 2002, 05:41 PM   #8
dice45 is offline dice45  Germany
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Default CD flaws

Hello Jason,





nice tie you'r wearing around your neck today, Uber-Fanatic


call you if i need a pencil holder, custom-made models avaiable?


ROTFLMAO!





hello all,


CD flaws:


during uiniversity i was working student at a company developing and manufacturing online inspection systems, laser scanners, and one of them was for inspection of CDs and other optical disks. The socalled "pin holes" in the reflective layer AudioKid was embarrased by are minor flaws if their diameter stays below 2.5 mm.





Surface scratches are more serious as the act as a µ-prism defracting the laser beam. Any surface degradation in fact acts as such, giving the CDPs error correction a hard time, the more, the harder the time.





This was clearly measurable on the inspection system as well as clearly audible: Have a thin to invisible layer of grease, butter, margarine, whatever on your CDs surface and compared to an unpolluted one you'll think this is a different CD.





A real mean thing are scratchy damages on the printed side of the CD as the reflective layer is protected by the print and a very thin layer of lacquer swirled on the surface. Those damages tend to grow. the reflective layer comes off in flakes although you do not se it at first. A very recommended way to meake data CDs permanently unreadable even by data recovery professionals, we tried that out back then. one radial scratch or two over the whole radius will do fine.





The highest/nastiest grade of flaws are inclusions in the polycarbonate itself close to the reflective layer, the less close, the worse they are.


They are not necessarily visible by the bare eye and their influece always extends more into the optical material than visible due to the mechanical stress extending in proximity up to several mm.


Those inclusions cause the optical properties of the polycarbonate to change dramatically as the material experiences mechanical stress during hardening. Results are refraction index changed, polarizing plane of the laser beam changed and dichroitic effects: refraction index is differently changed depending on the polarizing plane change, double refraction occurs or is changed.





Conclusion: Don't worry, be happy if you have only some tiny pinholes. TME returning the CDs to the shop helps little as the new CD then has the pinholes just in different location.


And I do not worry if my vinyls only have some tiny pressing bubbles
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Old 7th February 2002, 05:48 PM   #9
tiroth is offline tiroth  United States
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An excellant way of disposing of CDs/making neat coasters is to put them in the microwave for 10s or so. If you've never seen this effect before, I highly recommend it. Try doing it in someone else's microwave though. ;)
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Old 7th February 2002, 10:51 PM   #10
dice45 is offline dice45  Germany
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tiroth,




intentionally avoiding this hint, ....


but as we are on it, ever tried to cook potatoes or [evil ] eggs in another person's µwave?





Tell me when you do, i then sit in a little hut besides and sell tickets
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