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Tech: when a CD is 'read'

GUEST,leeneia 10 Dec 09 - 11:19 AM
olddude 10 Dec 09 - 11:21 AM
GUEST,leeneia 10 Dec 09 - 12:03 PM
GUEST,Ralphie 10 Dec 09 - 01:33 PM
Jack Campin 10 Dec 09 - 01:44 PM
treewind 10 Dec 09 - 01:46 PM
GUEST,Ralphie 10 Dec 09 - 01:48 PM
Skivee 10 Dec 09 - 08:06 PM
Jack Campin 10 Dec 09 - 08:30 PM
GUEST,Ralphie 11 Dec 09 - 04:33 AM
GUEST,Mr Red 11 Dec 09 - 07:31 AM
olddude 11 Dec 09 - 08:03 AM
GUEST,leeneia 11 Dec 09 - 09:35 AM
Uncle_DaveO 11 Dec 09 - 09:49 AM
Les from Hull 11 Dec 09 - 10:08 AM
Jack Campin 11 Dec 09 - 11:03 AM
GUEST,Ralphie 11 Dec 09 - 11:17 AM
McGrath of Harlow 11 Dec 09 - 06:42 PM
Gurney 12 Dec 09 - 12:27 AM
GUEST,Ralphie 12 Dec 09 - 02:20 AM
GUEST,leeneia 12 Dec 09 - 10:19 AM
robomatic 12 Dec 09 - 01:42 PM
Richard Mellish 12 Dec 09 - 03:52 PM
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Subject: Tech: when a CD is 'read'
From: GUEST,leeneia
Date: 10 Dec 09 - 11:19 AM

When I put a CD in my CD drive, does the machine read the data off the top side of it (where the label is) or off the bottom side?

I ask because I have a CD which someone put a return-address label on, and it's stuck there solidly. Does it matter?


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Subject: RE: Tech: when a CD is 'read'
From: olddude
Date: 10 Dec 09 - 11:21 AM

bottom shiny part is read


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,leeneia
Date: 10 Dec 09 - 12:03 PM

Thank you, olddude.


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,Ralphie
Date: 10 Dec 09 - 01:33 PM

Just to make this accurate. The digital information is just underneath the printed side....the rest of the underside of the disc is just protection. Hence the need for CD pens for homemade CDRs. (Early commercial CD's were printed with "Acid" inks, that burnt through the top side, destroying the data lurking underneath!).
And I've got several CDs that prove it!
So, I actually look after the label side of a commercial CD as well as the shiny side!!

Basically, they are delicate beasts. And affixing labels of any sort is not a good idea! If you have any of these, Transfer them to a hard drive as soon as possible.....The glue on the label will bleed eventually, maybe destroying the CD and damaging the M/C or computer that you are using.

And remember....NO BIROS!!!!

It's just the way that are made. It's just amazing that the buggers work at all!! Get a big hard drive, and copy all your favourites to that. Then you can use the CDs in the car or wherever, safe in the knowledge that you've got a back-up at home....

I've got very anal about this, and I've actually got 2 hard drive back-ups for my most treasured recordings. The second one is kept in the dark in a constant temperature room....I rarely look at it, but I know it's there if I need it!


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Subject: RE: Tech: when a CD is 'read'
From: Jack Campin
Date: 10 Dec 09 - 01:44 PM

No - the disc is read from the bottom, but the pits encoding the data are near the upper surface. The reflective coating is applied on top of the pitted area, a protective lacquer coating goes above that, and the label is printed on top of the lacquer. The whole thickness of the plastic is below the pitted and grooved surface.

What that means is that scratches on the bottom can often be polished out leaving the disc playable; the laser is focusing above it. Damage to the top surface is usually terminal.

A stuck-on label can destroy a high-speed computer CD drive if it's in any way asymmetrical or if it extends to the very edge of the disc. A disc like that should work in a single-speed audio player.


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Subject: RE: Tech: when a CD is 'read'
From: treewind
Date: 10 Dec 09 - 01:46 PM

Hi Ralphie.
You should take your hard drive out of cold storage occasionally and spin it up to make sure it still works. Someone in another forum recently has been saying that of all the (many, with audio files on them) drives that he had on the shelf long-term, a few have failed and the failure mode in every case was totally dead on power up.

Older hard disks had spindle lubricants that could set solid if they weren't used for a long time; modern drives are less prone to sticking like that, but even so it's worth checking...

Needless to say, Ralphie is spot-on about CDs.

Anahata


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,Ralphie
Date: 10 Dec 09 - 01:48 PM

Hello Jack...
Thats what I was trying to say!
You just said it better...Thank you!
Ralphie


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Subject: RE: Tech: when a CD is 'read'
From: Skivee
Date: 10 Dec 09 - 08:06 PM

Leeneia, have you considered soaking the label off, and carefully removing the adheasive withan appropriate solvent (suggestions welcome).


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Subject: RE: Tech: when a CD is 'read'
From: Jack Campin
Date: 10 Dec 09 - 08:30 PM

What I would do in this situation, assuming the sticky label is on the top side of the CD:

- find a computer with a single-speed audio CD drive attached to it. Whatever you do, DON'T put it in something that might spin it up to 24x or 48x.

- try the CD in that, and if it works, make a copy.

- only use the copy from there on.

- experiment with solvents to remove the label once you've got a usable copy - white spirit will usually soften sticky label glues, but it's anybody's guess what it'll do to the lacquer on top of a CD.

If the label is on the bottom, you have to remove it to get anywhere. Try white spirit, taking care not to get it on the top of the disk. This will not do *immediate* harm to the plastic of the disc. CDs are made of polycarbonate, which isn't very soluble in common solvents but does get degraded by them (and by UV light). One likely failure mode is for the disc to explode into a zillion splinters when you try playing it a year down the road, wrecking your drive. So make a copy and use that.


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,Ralphie
Date: 11 Dec 09 - 04:33 AM

Thanks Anahata. I do give my back up a spin from time to time, for exactly the reasons stated!
As for the original posters problem. Again agree with Jack. Carefully clone the cd if possible...If it's a really important recording, clone it several times!!.
If the original develops a fault, it's gone forever.
I've got reel to reel tapes, that I've cloned firstly to DAT, then CD, Then Hard Drive, and Hard drive backup. And you know what? I've still kept the original Tapes! Just in case!
Digits are marvellous when they work, and no use to man nor beast when they don't!


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,Mr Red
Date: 11 Dec 09 - 07:31 AM

modern CD's - the high speed ones - use as many as 9 layers of some pretty toxic materials. It is the aluminium reflective layer (or the aluminum layer in the US) that can be etched. Commercial CD's use pressings but the aluminium serves the same reflective purpose.

This etching crops-up every so often. Philips found out it was the ink permeating through the varnish covering the aluminium after a few years (maybe 5) but as the CD's become ever cheaper manufacturers try to cut corners and the new whizz kids learn that they are not as whizz as they thought - by which time they are long gone and so is your archive!

Poppy Records use CD's that are touted as lasting 300 years. Accelerated tests (temperature, humidity etc) probably indicate this is not too far out. I can never remember their name but it is probably HD or HRD or some such. They sell in the UK - that I do know.


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Subject: RE: Tech: when a CD is 'read'
From: olddude
Date: 11 Dec 09 - 08:03 AM

If you are having trouble reading the CD, try this wet the CD
take some toothpaste on your finger and gently rub in a circular motion
completely rinse and pat dry with a soft towel ... light scratches can be repaired using this method and it generally works. If the scratches are deep, it won't help but for me, most of the time it works fine


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,leeneia
Date: 11 Dec 09 - 09:35 AM

Thanks, everyone. The particular CD I was mentioning seems to be useless. Fortunately, it's merely drivers for my printer, so I can get the data online from the manufacturer.

It's been interesting to read all the information here about CD's.

My husband likes to check out movie DVD's from the library, and they are prone to have scratches. We'll try the toothpaste method on particularly bad ones.


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Subject: RE: Tech: when a CD is 'read'
From: Uncle_DaveO
Date: 11 Dec 09 - 09:49 AM

Jack Campin, what material do you mean by "white spirit"?


(I'm assuming not a Caucasian ghost).

Dave Oesterreich


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Subject: RE: Tech: when a CD is 'read'
From: Les from Hull
Date: 11 Dec 09 - 10:08 AM

White spirit in the UK is also known as 'turpentine substitute' (turps sub) and is the stuff you thin down oil-based paints with, or use to clean paint brushes.

Other useful solvents for getting sticky labels off are petrol (what you Mericans call gasoline) and methylated spirit. But you should always test a solvent on whatever the label is stuck to in such a way as to not kill what you are trying to take the label off. Acetone (nail varnish remover) is a no-no - it eats most plastics.


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Subject: RE: Tech: when a CD is 'read'
From: Jack Campin
Date: 11 Dec 09 - 11:03 AM

I thought this was worth testing, so I just wiped a CDR (Maxell CDR 80 700MB) very thoroughly with acetone-based nail polish remover. It played perfectly. Wiped it over thoroughly with white spirit. It still plays perfectly.


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,Ralphie
Date: 11 Dec 09 - 11:17 AM

Hi leenia.
Hope all of this stuff will come in useful in the future.
One final thing. DVDs by their very nature hold far more digital information than CDs, and are far more vulnerable as a consequence so I treat them with extra special care!!!
Don't use them as Frisbees!!
Good Luck.


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Subject: RE: Tech: when a CD is 'read'
From: McGrath of Harlow
Date: 11 Dec 09 - 06:42 PM

"Don't use them as Frisbees!!" Surely that depends on the DVDs?


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Subject: RE: Tech: when a CD is 'read'
From: Gurney
Date: 12 Dec 09 - 12:27 AM

I have had a couple of privately recorded CDs that have had the silver layer blister, and in one case it actually peeled off, leaving a transparent disc. Like the one you sometimes get on top of a 'spindle' of blank disks.

Delicate beasts indeed.

Also, turpentine substitute melts some plastics, makes others brittle. To remove labels, you could try paraffin/kerosine for the adhesive, followed by meths/ethanol for the paraffin. But only if you are desperate.


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,Ralphie
Date: 12 Dec 09 - 02:20 AM

Yes, McGrath, I'll make an exception for boxed sets of the "X Factor" !


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Subject: RE: Tech: when a CD is 'read'
From: GUEST,leeneia
Date: 12 Dec 09 - 10:19 AM

You mean, I can't even use my husbands complete collection of Tremors movies as Frisbees?

There is no justice in this world!


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Subject: RE: Tech: when a CD is 'read'
From: robomatic
Date: 12 Dec 09 - 01:42 PM

In endorsing Ralphie's post, I want to mention that CDRs that one purchases come in a variety of qualities. I purchased a stack of 'em from one of the office supply chains and found their recording layer was a thin sheet of foil like metal virtually sprayed across the top. Any deformation to it at all resulted in a gone disk. I returned them with prejudice.

I have also digitized and backed up old pre-recorded magnetic tapes that were beginning to degrade. My family had gone to reel to reel tapes for hi fidelity back in the late 60's. Some of these were lovely stereo Gilbert and Sullivan recordings from the Martin Gardner era. I learned to 'bake' the tapes in order to get the music off of them. (All of the Decca tapes were in like new condition).

That said, I think magnetic media get undeserved bad press these days, on the whole they are reliable long term methods of storing data. Hard drives have one moving part and can take years and years of use. Just don't drop them onto hard surfaces from great heights. I've got 40 year old cassette tapes by Sony, TDK, and Maxell that are in great shape. (other brands, not so much).

As for the hard drive 'stick' problem. That dates from the late 80's. My very first hard drive from La Cie suffered from that. I was able to get it to work by spinning the drive quickly, then plugging it in. I've had hard drives fail since, but not due to stickiness.

For long term, the 'problem' is that data formats and hardware formats change. My first hard drive connected to my computer using something called SCSI (pronounced 'scuzzy'). The more or less universal interconnect these days is USB 2.0, to be eclipsed, probably by USB 3.0. But the CD itself is not going to be a long term format, unlike the LP, long playing record.

So there is no 'save and forget' method. One has to save the material, and save the method of recovering the material. Or at least verify that one can transform the data into whatever comes next.

At some point we'll all probably have as external drives a 1 inch cube of plastic appearing material which costs a couple of bucks and holds a dozen petabytes, and the kids won't listen to stereo music or watch HD vid because they'll have animated holograms to listen to and view and interact with.


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Subject: RE: Tech: when a CD is 'read'
From: Richard Mellish
Date: 12 Dec 09 - 03:52 PM

To continue the discussion about backing up: I recently had to decide how best to archive some old dance videos that have just been converted from VHS to DVD. I've gone for redundancy and diversity.

For each video I have made one copy on an "archival quality" DVD-R, one copy on an "archival quality" DVD+R of a different brand and, for good measure, a .iso DVD image on a hard drive.

This article argues that DVD+R is inherently better than DVD-R, but I decided I might as well use both.

Richard


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