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

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

How are Grade A, Grade B, and Grade C CD-R discs defined? Are they all usable?

ISO Standard ISO/IEC 10149, and the Philips Red Book and Orange Book Part II contain more than fifty physical, optical, and electrical quality requirements that CD-R discs must pass. None of these Standards define grades such as A, B, or C. Such grades are determined arbitrarily by manufacturers. Grades can vary between vendors, and may change with time.

One quality requirement of the Standards limits visual defect diameters. Bubbles must be less than 0.1 mm in diameter, while black spots must be less than 0.3 mm in diameter. Most manufacturers optically scan all discs immediately after they are made, and should reject discs having visual defect diameters greater than allowed values. Manufacturers may sort optically scanned discs into Grade A discs that pass, Grade B discs that have few visual defects, and Grade C discs that have more defects.

Although Grade B or C discs may function, they probably do not meet visual defect requirements of the Standards. Successful interchange and longevity is not predictable for such discs. When discs have been graded only for visual quality, even Grade A discs may not meet all other requirements, such as radial tracking (push-pull) and jitter, that must be satisfied to assure interchange and longevity.

CD-R grading systems are not useful for quality purposes. First, grade specifications are not consistently defined, and are meaningless for brand comparisons. Second, grading systems based only upon visual defects ignore other critical quality requirements. Third, lesser grades imply media defects, and should never be used when interchange and longevity are important.

Manufacturers who use grading systems may be forced to do so when quality is low. Instead of scrapping frequent rejects, they can be reclassified into lower grades and sold at discounted prices. CD-R buyers concerned about quality should seek manufacturers that can consistently supply media that satisfies all quality requirements of the Standards. Low priced grade B or C discs may be expensive in the long run when duplication and user problems appear.