Wednesday, March 08, 2017

The Hidden Phenomenon That Could Ruin Your Old Discs

The Hidden Phenomenon That Could Ruin Your Old Discs. Ernie Smith. Motherboard. February 6, 2017.
     An article about regular CD and DVD optical discs and the problems that cause them to deteriorate.  "CDs and DVDs were sold to consumers as these virtually indestructible platters, but the truth, as exemplified by the “disc rot” phenomenon, is more complicated."  Early research showed that problems with the reflective layer could make the disc fail in 8 - 10 years. Or the degradable dye used in record-able discs will break down. The disc degradation sometimes looks like a stain or discoloration, or tiny pin pricks on the disc surface. "The eventual decay of optical media is a serious situation, whether you're a digital archivist or simply someone who wants to watch a movie on a weird format like a Laserdisc."

A Library of Congress preservation specialist said that the disc destruction showed up in three different forms: the "bronzing" of discs;  small pin-hole specs located on the discs; or "edge-rot".
Five facts about disc rot, according to the Library of Congress:
  1. Discs with significant errors are often still at least partially readable. This depends on the type of disc and where the error occurs.
  2. A scratch at the top of a CD is more problematic than one on the bottom, because scratches to the top surface can penetrate through and damage the reflective layer.
  3. DVDs generally have better integrity than do CDs but layers can delaminate over time. Dual-layer discs tend not to hold up so well.
  4. Recordable discs, and particularly DVDs don't last as long, due to the degradation of the organic dye used. A poorly recorded disc tends to wear out more quickly.
  5. Proper storage and handling helps. A well-made commercially pressed disc can last many decades if stored and handled properly. Discs stored in harsh environmental conditions with elevated temperature and/or humidity will have shorter expected lifetime.

No comments: