CD/DVD Degradation

Degradation in optical media refers to the decline of the physical quality of CDs, DVDs and Blu-rays over time and can be ascribed to material and environmental factors.

Material factors include:

Environmental factors include:

Examples of Damaged CD DiscsImproper handling or storage will also contribute to a faster deterioration process of CDs, DVDs and Blu-rays. Conversely, no matter how well discs are treated by the user, degradation can only be controlled to a certain extent, as they have a limited shelf life. The core recording layers of a disc will naturally break down before the outer plastic substrate layers. The outer polycarbonate substrate incurs damage mainly from rough handling, and is therefore not considered when measuring the disc's overall shelf life.

The first signs of disc degradation are typically imperceptible because any abnormalities are detected and corrected by the media's inherent error system. Through further decay, a user will be able to pick up jitters and other errors which mean the error coding system is losing its ability to function. The more errors that subsequently arise, the closer the disc is to being ineffective for use.

The variation in compositional elements between the formats of CDs, DVDs and Blu-rays contributes to what is specifically responsible for the disc's degeneration. For example ROM, R and RW/RE formats will have varying levels of decay. CD-ROM/DVD-ROM/BD-ROMs contain a metal alloyed data layer derived from aluminum. Consequently, degradation occurs when this metal oxidizes and reduces the layer's shine. Without the shine, there's less reflectivity which translates to a laser's inability to properly read reflected data.

CD-R/DVD-R/BD-R employs recording layers made with dye that can be prone to accelerated decay. Since the dye is chemically altered when a drive's laser reads or writes its data, it is extremely photosensitive. Even mild exposure to UV rays can affect the longevity of the discs. The disc's reflective side will visibly convey dye degradation over time through dark color discrepancies that don't match the green, gold, blue or silver appearance of a new disc.

The composition of CD-RW/DVD-RW/BD-RE has two primary factors working against a prolonged shelf life: metallic alloyed layers and a phase changing alloyed layer. The phase changing alloy lacks the stability of discs that employ dye, making them prone to major damage from UV light. The oxidation of the metallic reflective layers additionally counts against its potential for longevity. RW discs are also not purposed for long term or archival use. Their erasable and re-recordable nature is limited to less than 1,000 rewrites, meaning after they reach this capacity, their ability to function is degraded.

For more information on the proper care and handling of CD and DVD optical discs, please visit the guide entitled Care and Handling of CDs and DVDs published by the National Institute of Standards and Technology.

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