Which side of a CD is more serious if it is damaged?

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Offline Carolyn

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Last night, while my computer guy was visiting, I took a copy of my most favorite CD out of my computer and handed it to him.  This is my favorite CD.  It's only been out of the case once, when I copied it to ITUNES and when I made a backup copy.



I didn't have the cd case so I told him to just sit it on the shelf with the label down.  He then informed me that scratching the top side/printed side was more detrimental to the CD than scratching the bottom, shiny side.  I've never heard this before.  Is it true and if so, then why?
« Last Edit: 04/07/2008 23:29:55 by chris »
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Offline Karen W.

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Re: Which side of a CD is more serious if it is damaged?
« Reply #1 on: 18/10/2007 02:14:48 »
I have never heard of that either???

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Offline kdlynn

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Re: Which side of a CD is more serious if it is damaged?
« Reply #2 on: 18/10/2007 02:15:20 »
well that doesn't make sense

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another_someone

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Re: Which side of a CD is more serious if it is damaged?
« Reply #3 on: 18/10/2007 03:34:38 »
He was correct.

The label side has a reflective coating that reflects the light, and if this is damaged it can harm the CD.  The transparent side is just transparent plastic, and although light has to travel through it, the light is not focused onto it - it is focused on the coating on the back.  Because the light is still defocused as it passes through the transparent side of the CD, and scratch on there is also defocused, so will not have as acute an effect as if the scratch was at the point of focus (a bit like a spec of dust on a camera lens is less pronounced in its effect than a spec of dust on the film itself, because the light at the lens it not at the point of focus).

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Offline kdlynn

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Re: Which side of a CD is more serious if it is damaged?
« Reply #4 on: 18/10/2007 03:39:22 »
wow

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Offline Carolyn

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Re: Which side of a CD is more serious if it is damaged?
« Reply #5 on: 18/10/2007 03:40:46 »
Thanks George...for moving it to the correct place and for the answer.   So if I scratched a CD on top, then could I see through it?
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another_someone

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Re: Which side of a CD is more serious if it is damaged?
« Reply #6 on: 18/10/2007 04:21:48 »
Thanks George...for moving it to the correct place and for the answer.   So if I scratched a CD on top, then could I see through it?

If you scratched enough off the top, probably so - but I have never tried it (although I nicely scratched up an MO disk on the top because I wanted to throw it out, and it was too difficult to take it apart and snap it - and I wanted to be sure it was not readable after throwing it away).

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Offline DoctorBeaver

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Re: Which side of a CD is more serious if it is damaged?
« Reply #7 on: 18/10/2007 12:59:31 »
I never knew that. Thank you for the info.
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Offline Alandriel

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Re: Which side of a CD is more serious if it is damaged?
« Reply #8 on: 18/10/2007 14:41:45 »

    [8D] [8D] [8D] great info!

    Thanks George ♠
     [:)]







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Offline Karen W.

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Re: Which side of a CD is more serious if it is damaged?
« Reply #9 on: 18/10/2007 14:52:55 »
Yes it was ..Thanks George!

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Offline techmind

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Re: Which side of a CD is more serious if it is damaged?
« Reply #10 on: 18/10/2007 23:51:33 »
So if I scratched a CD on top, then could I see through it?
Yes.
"another_someone" is correct

The data is pressed into the top (label) side of the disc, then (as I understand it) the top of the disc is "silvered" (it's actually aluminium for standard read-only CDs), then a protective lacquer is applied on top of the aluminium. If you scratch the top (label) side of a CD, you can fairly easily break through the laquer and metalisation - try it with an unwanted free CD from a magazine - you can then see through it :-)  but data will be very likely lost (minor damage can be corrected by the error-correction system). Even minor damage to the laquer can let oxygen at the metallisation, causing it to oxidise and lose its shininess, and cause wider damage over a longer timescale...

If you try bending an unwanted recordable CD, the gold/silver metallisation and laquer layers flake off, leaving a mostly transparent disc.
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Offline techmind

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Re: Which side of a CD is more serious if it is damaged?
« Reply #11 on: 18/10/2007 23:53:45 »
Apparently Philips had a very fundamental patent on the concept of recording a CD on the top side and reading it through the plastic substrate. The 25-year patent expired recently, losing them a nice stream of royalties...
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Offline neilep

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Re: Which side of a CD is more serious if it is damaged?
« Reply #12 on: 19/10/2007 01:32:08 »
Yes....I told George all of that of course !!

So, ewe should all thank me too !!

...great CD Carolyn......me has it too

YAYYYYYYYYYYYYYYY !!

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Offline Carolyn

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Re: Which side of a CD is more serious if it is damaged?
« Reply #13 on: 19/10/2007 01:53:23 »
Yes....I told George all of that of course !!

So, ewe should all thank me too !!

...great CD Carolyn......me has it tooYAYYYYYYYYYYYYYYY !!



Great minds don't cha know! 

THANK YOU NEIL for giving George the answer!  It's most appreciated! [;)]
Carolyn

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Offline rosalind dna

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Re: Which side of a CD is more serious if it is damaged?
« Reply #14 on: 30/06/2008 10:35:12 »
Something that I have wondered about for ages, which is this:

How does the CD and DVD drivers in my PC read both sides of the CD or DVDs ??

By the way, I only have the single  CD/DVD drivers in the XP PC.

I can't rewrite them to make backup copies except in the PC.

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Offline turnipsock

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Re: Which side of a CD is more serious if it is damaged?
« Reply #15 on: 01/07/2008 13:40:34 »
I didn't have the cd case so I told him to just sit it on the shelf with the label down.  He then informed me that scratching the top side/printed side was more detrimental to the CD than scratching the bottom, shiny side.  I've never heard this before.  Is it true and if so, then why?

You mean you didn't read the banana/scratches/CD thread that Neil started a while ago?

Where is he anyway, you would think he would have said if he was going away anywhere.
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