Last-modified: 1997/09/14
Version: 1.11

[7] Media

[7-1] What kinds of media are there?

[7-2] Does the media matter?

[7-3] Who manufactures CD-R media?

[7-4] Which kind should I use?

[7-5] How long do CD-Rs last?

[7-6] How much data can they hold?

[7-7] Is it okay to write on or stick a label on a disc?

[7-8] How do CD-Rs behave when microwaved?

[7-9] What can I do with CD-R discs that failed during writing?

Subject: [7] Media

Subject: [7-1] What kinds of media are there?

There are gold/gold, green/gold, and silver/blue CD-Rs. "Gold" and "Green" discs both use a gold reflective layer (yes, it's real gold), but the cyan-colored dye makes the discs look green.

The silver/blue CD-Rs (metalized azo dye, also based on cynanine, with a silver alloy substrate) are relatively new. They appear to have a very low BLER (BLock Error Rate), come with a scratch-resistant coating, and are reputed to be more resistant to UV radiation, but their lifespan relative to green and gold media has yet to be determined. The process is patented by Verbatim.

Some CDs have an extra coating (e.g. Kodak's "Infoguard") that makes the CD more scratch-resistant, but doesn't affect the way information is stored. The top (label) side of the CD is the part to be most concerned about, since that's where the data lives, and it's easy to damage on a CD-R. Applying a full circular CD label will help prevent damage.

http://www.mitsuigold.com/ has some info on MTC media.

Subject: [7-2] Does the media matter?

1. Does it work with your recorder?
2. Which CD readers can use it?
3. How long does it last before it starts to decay?
4. What's the typical block error rate for the media?

Some audio CD players (like the ones you'd find in a car stereo) have worked successfully with one brand of gold media but not another. Some players fail completely with green, some fail completely with gold, some only work with blue.

Some people have found brand X CD-R units work well with media type Y, while other people with the same unit have had different results. Recording a disc at 4x may make it unreadable on some drives, even though a disc recorded at 2x on the same drive works fine.

To top it all off, someone observed that discs burned with one brand of CD-R weren't readable in cheap CDROM drives, even though the same kind of media burned in a different device worked fine.

A number of specific discoveries have been posted to Usenet, but none of them are conclusive. Many people have reported that Kenwood CD players don't deal with CD-Rs very well, while Alpine units play nearly everything.

Some users have found that the *quality* of audio recordings can vary depending on the media. Whatever the case, if you find that CD-Rs don't sound as good as the originals, it's worthwhile to try a different kind of media or a different player. See section (4-18) for other ideas.

One final comment: while there are clearly defined standards for CD-R media, there are no such standards for CD and CD-ROM drives -- other than that they be able to read CDs. It is possible for media to be within allowed tolerances, but be unreadable by a CD-ROM drive that can handle pressed discs without trouble. All you can do in this sort of situation is find a better-quality CD or CD-ROM drive, or switch to a brand of media whose characteristics are on the other side of the tolerance zone.

Subject: [7-3] Who manufactures CD-R media?

Mitsui Toatsu Chemicals (MTC) made the first "gold" CDs. They are now manufactured by Kodak and possibly others as well.

Verbatim made the first "blue" CDs. They are the only manufacturer.

Most CD-R brands (e.g. Yamaha and Sony) are OEMed from one of the above manufacturers. Attempting to keep track of who makes what is a difficult proposition at best, since new manufacturing plants are being built, and resellers can switch vendors.

Subject: [7-4] Which kind should I use?

Gold media has a longer lifespan and may work better in higher speed recording. Mitsui's gold/gold discs are recommended by some vendors, and in some informal and unscientific tests were more compatible with car CD players than Kodak gold or TDK green discs.

Trying samples of blanks is strongly recommended before you make a major purchase. Remember to try them in your reader as well as your writer; they may not be so useful if you can't read them in your normal CDROM drive.

Maxell's CD-R media earned a miserable reputation on Usenet. In April '97 Maxell announced reformulated media ("gold" discs) that seems to work better than the previous ones ("green" discs).

A survey can be found at http://www.tcp.co.uk/~blades/cdr/.

See also Is There a CD-R Media Problem? by Katherine Cochrane, originally published in the Feb '96 issue of CD-ROM Professional magazine.

Subject: [7-5] How long do CD-Rs last?

Exposing the disc to excessive heat, humidity, or to direct sunlight will greatly reduce the lifetime. In general, CD-Rs are far less tolerant of environmental conditions than pressed CDs, and should be treated with greater care.

Keep them in a cool, dark, dry place, and they will probably live longer than you do.

One user was told by Blaupunkt that CD-R discs shouldn't be left in car CD players, because if it gets too hot in the car the CD-R will emit a gas that can blind the laser optics. However, CD-Rs are constructed much the same way and with mostly the same materials as pressed CDs, and the temperatures required to cause such an emission from the materials that are exposed would melt much of the car's interior. The dye layer is sealed into the disc, and should not present any danger to drive optics even if overheated. However, leaving a CD-R in a hot car isn't good for for the disc, and will probably shorten its effective life.

See also http://www.cd-info.com/CDIC/Technology/CD-R/Media/Longevity.html.

http://www.onlineinc.com/cdrompro/0296CP/02parkerstarrett.html has a very readable description of CD-R media error testing that leaves you with a numb sense of amazement that CD-Rs work at all. It also explains the errors that come out of MSCDEX and what the dreaded E32 error means to a CD stamper. Highly recommended.

Subject: [7-6] How much data can they hold?

CD-Rs may advertise that they hold 650MB, 680MB, or even 700MB of data, even though they all claim to hold 74 minutes of audio. The reality is that they're all almost exactly the same size, and you're not going to get more data onto a 74-minute disc by buying a different brand.

Folks interested in "doing the math" should note that only 2048 of each 2352-byte sector is used for data on typical (Mode 1) discs. The rest is used for error correction and other misc fields. This is why you can only put 650MB of data on a disc that will hold 740MB of audio.

It should also be noted that hard drive manufacturers don't measure megabytes in the same way that CD-R and RAM manufacturers do. The "MB" for CD-Rs and RAM means 1024x1024, but for hard drives it means 1000x1000. Keep this in mind when purchasing a hard drive that needs to hold an entire CD. A data CD holds about 682 "disk" MB of data.

Some programs, such as Easy-CD Pro 95, will tell you the exact number of 2K blocks available on the CD. (With Easy-CD, put a blank disc in the CD-R and go to the "Disc Info / Tools" menu item.) It's difficult to draw conclusions from the results though. An article in the June issue of EMedia Professional found that not only does disc capacity vary from brand to brand and batch to batch, it may even vary depending on which model of recorder is used to examine the disc.

An informal survey conducted by one user found that the deviation between the largest and smallest CD-R was about 3500 blocks (47 seconds, or 7MB), which while not inconsequential is nowhere near the difference between 650MB and the 680MB or 700MB figures quoted by some manufacturers. All discs had at least 333,000 blocks, as required by the Red Book specification. (Before you ask which discs held the most data so you can run out and buy them, I should mention that the person doing the survey had trouble mounting some of the higher-capacity discs. Getting those few extra seconds may cost you in other ways.)

The PCA (Program Calibration Area), PMA (Program Memory Area), TOC (Table of Contents), leadin, and leadout areas don't count against the 74-minute rating on single-session CDs. You really do get all the storage that the disc is rated for. Bear in mind, however, that the "cluster" size is 2K, and that the ISO-9660 filesystem may use more or less space than an MS-DOS FAT or HFS filesystem, so 650MB of files on a hard disk may occupy a different amount of space on a CD.

On a multisession disc, you lose about 23MB of space when the first session is closed, and about 14MB for each subsequent session. A common mistake when writing multisession CDs is to overestimate the amount of space that will be available for future sessions, so be sure to take this into account.

Factory-recorded CDs also hold up to 74 minutes of data (but see section (3-8)).

Subject: [7-7] Is it okay to stick a label on the disc?

Specific information can sometimes be found on the back of the jewel case that the discs come in. The TDK CDR-74 discs have the following warning:

        [...]
        2. Do not attach labels or protective sheets, or apply any coating
        fluids to the disc.
        3. When writing titles and other information on the label (gold)
        side of the disc, these should be written in the printed area using
        an oil-based felt-tipped pen.
        [...]

Other brands say "use a permanent felt-tipped pen" or words to the effect that the ink shouldn't smudge. Most important part is to use a felt tip pen and not a ball-point, because the top layer is somewhat delicate. Several people have reported good luck with Sanford "Sharpie" pens, but make sure you don't etch the surface accidentally if you have an "Ultra Fine" pen.

Dixon Ticonderoga sells a water-based felt tip marker called "Redi Sharp Plus" that is both permanent and smear-proof. It's widely recommended.

So long as you keep all of the above in mind, it's okay to write directly on the top surface of the CD, label or no. If the prospect makes you nervous, just write in the clear plastic area near the hub instead.

Only use labels made specifically for recordable CDs. Attempting to remove the label once attached is probably a bad idea. ProSource Sales & Marketing, Inc. (http://www.inter-look.com/prosource/) sells labels and an applicator that are reputed to work well. See also http://www.neato.com/ for information on the NEATO CD-Label kit (complete with animated illustrations), and http://www.labelcd.com/ for the CD Stomper Pro. If you speak Italian, try http://www.ufocd.com/.

You can also buy printers that will write directly onto a CD-R with a printable surface. One example is http://www.fargo.com/.

A wealth of information on CD-R labeling options can be found here: http://www.cd-info.com/CDIC/Technology/CD-R/Labeling/

Subject: [7-8] How do CD-Rs behave when microwaved?

The basic process is, take a disc that you don't want anymore, and put it shiny-side-up on something like a mug of water so it's nowhere near the top, bottom, or sides of the microwave. (Actually, you may want to leave it right-side-up if the disc doesn't have a label, because the foil is closest to the top of the CD). Turn off the lights. Program the microwave for a 3-second burst, and watch the fireworks.

Performing this operation on replicated CDs results in blue sparks that dance along the CD, leaving fractal-ish patterns etched into the reflective aluminum. For those of you not with the program, this also renders the CD unreadable.

Trying this with a green/gold CD-R gives you a similar light show, but the destruction patterns are different. While pressed CDs don't show much of a pattern, the TDK green CD-R I'm looking at (stupid Incat error handling) shows some definite circular patterns. Ditto for a Mitsui gold.

On a different note, CD-Rs seem to smell worse, or at least they start to smell earlier, then replicated CDs. The materials used are non-toxic ("cyanine" comes from the color cyan, not from cyanide), but breathing the fumes is something best avoided.

Subject: [7-9] What can I do with CD-R discs that failed during writing?

However, that doesn't mean it's useless. Here are a few ideas:

• Fill in the center hole to avoid leaks, and use them as drink coasters.
• Create a hanging ornament or wind chime. The latter isn't all that interesting - they just sort of "clack" a little.
• Use them as mini-frisbees in an office with cubes. Since they're rather solid and may hurt when they hit, you should await a formal declaration of intra-office war before opening up with these.
• Have CD bowling tournaments where you see how far you can roll one down a narrow hallway. You'd be surprised at how hard it can be unless you get the wrist motion just right.
• Put them under a table or chair whose legs don't quite sit right.
• Run them through one of those industrial-strength paper shredders (the kind with the rapidly spinning wheels) to get shiny green or gold confetti.
• Make really, really big earrings.
• Try to convince people at the beach that it's a shell from a new species of abalone.
• Hook them into your bicycle spokes as reflectors.
• Use them as wheels on a toy car. (If you had buggy firmware, you're probably stocked for a toy 18-wheeler.)
• Build a suit of "CD-R chain mail" for laser-tag games.
• Use them as art-deco floor or ceiling tiles.
• Hang them from the rear view mirror in your car.
• Cut it into a jigsaw puzzle with a small wire saw.
• Try out the "helpful CD repair" suggestions that periodically crop on the newsgroup. Like the ones that suggest using acetone and sandpaper to refinish a scratched CD-R.
• Hang them in your car windows. Some people believe that CDs will defeat speed guns and automated speed traps that use flash photography.

In one carefully controlled experiment it was determined that CD-Rs behave differently from pressed CDs when you slam them edge-on against the ground. The aluminum ones will chip (once you throw them hard enough, otherwise they just bounce) and create silver confetti. The gold one I tried chipped and the gold layer started peeling, leaving little gold flakes everywhere. One user reported that a Verbatim blue CD developed bubbles even though the plastic was intact. More experimentation is needed (but not around pets, small children, or hard-to-vacuum carpets).

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