Frequently Asked Questions About CD-R and CD-RW Discs

Please contact Media Sciences if your questions are not answered on these pages.

Who makes good CD-R and CD-RW discs? How can I be certain they will work in my writer?

CD-R discs are great for premastering and for limited data or software distribution. CD-RW media is convenient for mass storage of information that is frequently updated. Such applications demand the best possible quality. Unfortunately, confusion exists regarding media quality (see CD-R Media Survey.) For various reasons, Media Sciences does not recommend specific brands. Suppliers may offer multiple part numbers, sometimes from different processes or production lines. Conflicting opinions from "experts" create uncertainty. One basic answer emerges from the confusion. You should not buy discs based only brand name. Instead, take a system approach. Use a high quality service agency or purchase a writer, software, and discs from a reputable, experienced system integrator. Obtain a package that works, instead of reinventing the wheel by attempting to become an expert in a field that contains few experts.

In contrast to the relatively stable CD-ROM field, CD-Recordable/ReWritable are rapidly evolving technologies. There are no public standards for CD-R and CD-RW discs, only proprietary Orange Book Part II and Part III. Even worse, no public or private standards exist for writers and players. Drive manufacturers often recommend Fuji, Hitachi Maxell, Kodak, Mitsubishi (Verbatim), Mitsui Toatsu, Pioneer, Ricoh, Taiyo Yuden, and TDK CD-R media. Some vendors may be listed only for 74 minute media, others for both 74 and 80 minute discs. Lot-to-lot quality of these brands may vary, while high quality discs may be available from manufacturers that are not on their lists.

Significant differences exist between writers. One might work well with certain discs and poorly with others. Another might be tuned for discs that gave poor results in the first one. Of course no one wants to wait one hour while a disc is recorded. Writers are now being spun at 16X and higher speeds, sometimes with excellent results but often with poor results at maximum, minimum, or intermediate speeds. Writers are rated by their maximum write speed, but lower speeds such as 2X or 1X may not be supported by the manufacturer. Only limited speeds may support CD-R packet writing. Bad discs may be detected only by another user, since readability in the recording drive may not detect certain flaws. More sophisticated tests are required to assure interchange in all drives.

CD-R media encompasses three technologies, each representing the particular dye used in the active layer. Both stabilized cyanine and phthalocyanine are popular dyes, while Mitsubishi uses an azo dye. The writing laser locally heats these infrared absorbing dyes and forms pseudo-pits through bleaching or the formation of voids. This process is very sensitive to laser power. Each dye type, and sometimes variations of a type, require different write strategies. Every CD-R contains a special power calibration area for write optimization, but not all writers use this area correctly.

CD-RW now has three technologies. Low speed media utilizes alloy layers optimized for 2X recording. Some recorders may be able to also write such discs at 1X or 4X, but cannot erase properly at higher recording speeds. New, hi-speed CD-RW discs use thinner alloy layers that are rated only for 4X/8X/10X recording. These discs will not be recognized by drives designed only for low speed CD-RW media, and must not be written in these 1X/2X/4X drives. The latest ultra-speed discs can be written only at 8X/16X/24X, and require compatible writers. Hi-speed and ultra-speed discs may not be available from all suppliers.

Even more confusing are longevity studies that predict 100+ year life for some "good" disc as compared to only 20 years for an inferior product. A few logical voices call attention to the fact that more attention should be paid to writing a very high quality disc and less attention to gamesmanship. Indeed, will drives be around in 100 or even 20 years that can read CD-R and CD-RW? Probably not! It would be difficult today to find readers for some programs that were recorded on punched paper tape 20 years ago. Additional information on longevity testing issues is on this web site.

Easy solutions to CD-R and CD-RW quality issues do not exist today. The technology is still evolving, and hopefully will soon stabilize. Users must carefully read both media and drive specifications before selecting a write speed. For now, the simplest approach is to have your discs written by a high quality service agency. An alternative would be to buy a complete recording system from an experienced vendor. In either case, testing by a qualified third party can provide data that generates confidence in your decision. The cost of validation is minor compared to the cost of field failures.

If it would help, Media Sciences will test one recorded sample at no charge. Please follow the free test instructions on our web site.