Is it possible to scratch a CD...
Jul 31, 2008 at 5:28 PM Post #16 of 34

Chri5peed

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Hmmm, never knew, I always assumed the laser couldn't scratch the disc?

Obviously anything of a harder material forcefully coming into contact with a softer one is going to cause a scratch.

I know often premium CD/DVDs are harder to scratch, must have a protective coating on them?
 
Jul 31, 2008 at 8:11 PM Post #17 of 34

obobskivich

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yeah, a lot of higher end media, including the more ritzy stuff you can buy yourself, comes with an applied protective coating over the disc, which protects the read side, but more importantly, the back side (theres only like 2-3 layers between the labeling and the data, vs on the read side you've got like 6 layers, I may have the #'s a bit inflated/deflated here)

and yeah, i've never heard of a laser actually coming up and hitting the disc, but it wouldn't surprise me given all of the cheap junk thats done today with C/E
 
Jul 31, 2008 at 10:40 PM Post #18 of 34

Chri5peed

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I don't have any idea where I got it from, so forgive me if it is mental.

On CD/DVDs is the data burnt on an inner layer? Well maybe not so crazy, as DVD9s have a layer underneath.
 
Jul 31, 2008 at 11:33 PM Post #19 of 34

obobskivich

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yeah, its like a few layers of plastic on either side, and theres a metalic/something substrate inside (the silver/gold part) thats got the data a layer or two underneath it

its easier to damage that layer by damaging the part of the CD that writing is usually put on, vs damaging it by damaging the side the laser reads through, in terms of totally messing the data up
 
Aug 1, 2008 at 8:11 AM Post #20 of 34

milkpowder

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Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif
yeah, its like a few layers of plastic on either side, and theres a metalic/something substrate inside (the silver/gold part) thats got the data a layer or two underneath it

its easier to damage that layer by damaging the part of the CD that writing is usually put on, vs damaging it by damaging the side the laser reads through, in terms of totally messing the data up



I've had the silver foil flake off the tops of two of my SACDs before. I would tape the area surrounding the missing bit (to prevent further flaking) and the SACD player would still play it! Error correction ftw
wink_face.gif


Quote:

Originally Posted by bergman2 /img/forum/go_quote.gif
having just recently transferred my entire 5,000 cd collection to my hard drives in wavs I had maybe a couple shot cd's and a dozen or more selected lost tracks....not bad for the volume of cd's i went thru...generally, the bottom layer of a cd is pretty beefy and can take punishment...a friend of mine used to work at an audio shop years ago and to tout the palayability and characteristics of cd's he would scratch the **** out of the cd on concrete and then put it in a player and play it---some of them got pretty beat up and they still played


Just because it plays in a CD player doesn't mean the data is still 100% intact. There's a lot of error correction built-in with the aim being to provide jitter-free playback even if certain bits have to be interpolated. Try putting the same badly scratched CD into your computer's CD-ROM drive and rip it using a secure ripper (eg EAC, CDex, etc). You'll probably find your CD-ROM drive spinning up and down trying to read the same bit over and over again, sometimes succeeding, other times not. Of course there comes to a point when not even error correction is enough to mask a scratch.
 
Aug 1, 2008 at 12:21 PM Post #21 of 34

obobskivich

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haha at the taping CDs, wouldn't that off-balance the weight of the disc and damage it inside of the transport, assuming it got going fast enough? (i know the old 52/56/63x CD-ROM drives would blow discs apart just because of moving so fast and how relatively imperfect the discs are for that kind of speed (the 72x kenwood is different, it uses 3 lasers at a slower speed))

so, i think what the general consensous of the thread is, is dont damage your CDs, but if you do, they're probably still readable, unless your transport is crazy in the head and wants to start reading your discs like vinyl because they've already got enough grooves to compete with an LP for total texture
 
Aug 1, 2008 at 12:38 PM Post #22 of 34

Jaska

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Quote:

Originally Posted by Golden Monkey /img/forum/go_quote.gif
I've had quite a few scratch from transporting in a car in their case from a broken spindle. The vibrations from driving around caused it to spin in the case, leaving those perfectly circular scratches.


So that's where they come from. I've seen countless CDs with perfectly circular scratches, usually towards the outer edge of the discs, when I've borrowed them from libraries. On average, I'd say that 2 or 3 out of 10 well- (or not-so-well-, depending how you look at it) used discs have these kinds of scratches. They invariably skip and suffer other various playback problems in my car player, where I use these borrowed CDs.

I have also had the misfortune of buying and receiving a couple of used discs with these types of scratches, and they required an undue amount of Brasso buffing work to repair properly.
 
Aug 1, 2008 at 12:48 PM Post #23 of 34

obobskivich

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another thing i've seen move CDs around, this is more data discs, you know those double or quad CD packs you get for software? if any static charge builds up between the two discs, if one of them moves, the other moves in opposition, i've actually seen all 4 discs move as a result of taking a disc out of one of those kinds of cases, after seeing that, i moved to CD folders to prevent any potential for damage

as far as repair, i thought of this earlier but didn't post it, a lot of used video game stores will offer cd restoration services, because they usually have a big commerical reparing machine (at least one of the ones here does) so they can buy scrapped up games and fix them to nearly new condition, so that might be worth it to restore your favorite disc (iirc its only like $0.50/disc here, might've gone up a little, its still far cheaper than buying new discs, especially if its a multi-disc set and only one is damaged) just take in something trivial and see if they do a good job, and if they do, might be worth a try

i've never heard of using brasso to fix CDs though, doesn't it eat right through them like it eats right through everything else?
 
Aug 1, 2008 at 12:51 PM Post #24 of 34

Jaska

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Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif
i've never heard of using brasso to fix CDs though, doesn't it eat right through them like it eats right through everything else?


Yes, it "eats" some of the plastic, which is necessary when removing the scratches. On deep scratches, there's still a whole lot of elbow grease (not sold in stores) involved.
 
Aug 1, 2008 at 1:03 PM Post #26 of 34

Jaska

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Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif
oh, so you're actually eating it thinner, like sharpening a knife to remove imperfections in the cutting edge, that makes sense, but i'm guessing after a point it just ruins the CD (Vs a knife, which takes a very long time to sharpen down to nothing (if you're doing it right))


That's it. I've never managed to blaze all the way through the (rather thick) polycarbonate layer of a CD with Brasso, and I think it would actually take a REALLY extended period of vigorous rubbing with Brasso to actually do this. I mean, your thumb would literally be sore for days.
 
Aug 1, 2008 at 2:08 PM Post #27 of 34

milkpowder

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Quote:

Originally Posted by Jaska /img/forum/go_quote.gif
That's it. I've never managed to blaze all the way through the (rather thick) polycarbonate layer of a CD with Brasso, and I think it would actually take a REALLY extended period of vigorous rubbing with Brasso to actually do this. I mean, your thumb would literally be sore for days.


k701smile.gif
It makes me laugh just thinking about how long it would take to rub through a CD.
 
Aug 1, 2008 at 3:05 PM Post #28 of 34

Chri5peed

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This thread is pretty informative.
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Aug 1, 2008 at 3:08 PM Post #29 of 34

obobskivich

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Quote:

Originally Posted by milkpowder /img/forum/go_quote.gif
k701smile.gif
It makes me laugh just thinking about how long it would take to rub through a CD.



see i was thinking about using something like a dremel with the polisher bit or something

or being cheaper, and doing something like this:
Clean your bathroom with POWAH

granted i wouldn't use a sponge but you get the point, lol
atsmile.gif
 
Aug 1, 2008 at 3:12 PM Post #30 of 34

milkpowder

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Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif
see i was thinking about using something like a dremel with the polisher bit or something

or being cheaper, and doing something like this:
Clean your bathroom with POWAH

granted i wouldn't use a sponge but you get the point, lol
atsmile.gif



Haha
darthsmile.gif


Chances are you'll melt the CD or at least warp it before you polish through it
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