Reading through many of the posts on this forum, it is obvious that many people are now using CD-R or CD-RW to back up data. I thought the following might be of interest.

I read an article some time ago, from an authoritative source, about problems associated with CD labels. It would seem that fixing labels to CDs, can in some cases, affect the life of the data recorded on a CD-R. The problem is apparently caused by the chemicals in the adhesive on some labels, gradually leeching through the upper surface of the CD and affecting the dye layer, on which the data is recorded. I only use 'PRESSIT' labels and when I read about this problem, I contacted the firm and asked for their comments. They replied that they had not experienced any problems associated with their adhesive and that all materials used in their labels were benign. However, they could not comment on other label manufacturer's products and were aware of the reported problem.
I tend to use blank CD-R which have a silk screen painted layer on the entire top surface. If using a label on these, it may provide an extra protective layer between the sensitive data layer and the paper label.

I don't know if you are familiar with the construction of recordable CDs ? The really durable part, believe it or not, is the Lower surface, since this is quite a thick piece of clear plastic, which makes up about 90% of the total thickness of the CD. The recordable dye layer, backed with a very thin silver layer, is actually on the Top surface and is very vulnerable to damage - much more so than the lower surface. I examined a CD-R, (which recorded badly and was just a 'coaster') by breaking it in two, and peeling the layers apart. As I said before, most of the thickness is just a clear plastic disc. The actual 'business' part on the Top layer, is VERY thin and has virtually no protection !

Having said that, scratches on the relatively soft lower surface, through which the laser reads the data in the dye layer, can attenuate, diffract or deflect the laser beam, resulting in faulty reading of the data. In the past, when I have had problems of this nature, I have managed to restore both commercially produced music CDs and CD-Rs to fully readable condition, using Metal Polish, to gently 'Buff out' the scratches. This only works with fairly light surface scratches, not deep damage and since the CD is already a bit of a lost cause, you have nothing to lose in trying to restore it!
Incidentally, this 'Label Adhesive' problem does not apply to commercially manufactured CDs, since they are produced by a totally different process.

Another point about labels, of which I am sure you are aware - it is very important that they are placed centrally on the CD, using a suitable tool. Any eccentricity between the CD-R and the label can cause quite severe vibration due to the high rotation speed in the drive. This can result in faulty reading of the data. This is even more important on recordable DVD, since they spin at even higher speeds. There have been reports about recordable DVDs being unplayable when labels have been applied, even when they were apparently fitted centrally. This was thought to be due to differing densities in the paper label causing uneven weight distribution across the DVD and therefore setting up vibration when it was spinning. Because the optical track widths on DVDs are much smaller than CDs, it does not take much in the way of eccentricity to cause bad reading. And of course, once these labels are fitted, you can't get 'em Off !!!!
The comments about chemical reaction probably applies equally to Recordable DVD.

I Hope the above may been of some use.

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Willum

If labels can affect the life of CDs, what can we do?
Use special pencils to write titles or files names? But these pencils perhaps can affect too the CD, because they have chemicals too.
So, what?

Hi All,

I'm not sure if this is true or not but it's a bit funny since one company and I believe it's HP now makes a CD writer that burns the label on to the top of the CD using a laser. No more paper labels. If I remember right it costs about $500.

So there is one alternative.

Heather

The lower layer is polycarbonate around a mm thick and thus tough and can stand some polishing (radial!). The top is generally a blob of lacquer or polymer which is spun on the reflective layer to even out the thickness with the label silk-screen printed on. I haven't seen many reports that cd marker pens harm the top layer, but there are reports of certain label adhesives reacting with the screen or lacquer, presumably from those manufacturers who perform no ageing tests on their products. I don't use labels because it is very difficult to centre them manually and they cut down your reading speed as often as not if slightly imbalanced, or at least cause servo hunting.

Thanks for adding your comments Alec. I use a very simple device for centering the labels. It came with the first 'Pressit' kit I bought and works really well.

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Willum

Hi Willum,
by manual I meant non-robotic (assuming the robot is accurately aligned!). Probably does not matter one jot on audio cds, although the 'golden eared' brigade might carp at extra servo power current modulating something or other when imbalanced, but matters if trying to read at 50x, and as you say a complete no-no on dvd - personal preferences

Hello!

This is just one more example, among hundreds, of the wonderful expertise our forum members/friends have and their willingness to share it. Thanks, folks.

Chuck

Bill N. Part of your statement appears to be true because my friend had problems burning a CDR after sticking on the label first. The CD burning process was reflecting back a different signal because of the label giving that extra thickness. I never now put labels onto CDR & CDRW's. I write on them with a proper pen designed for the job, then give the case a decent cover label.

Graham UK



[This message has been edited by Graham UK (edited 11-22-2003).]

I too have stopped using paper labels because I have found that many CD players like those use in Autos where you hold the CD to the slot and it pulls them in can not handle the paper. So if you do get them in to the player you may not get them back out. I had that happen twice before I stopped using them. Fortunately I managed to get them out but just barely.

Heather

I have just read the CD discussion and as the saying goes "you learn something every day"

I help run a keyboard club and we are just getting into CD recording and I am sure most of us are unaware of these problems so would it be in order for me to print out the comments and pass the information on to our members? I wouldn't want to upset anyone by doing this.

Aud