Several reports are indicating that the CD might not be as robust a long-term storage format as once thought.
While CDs are subject to scratches and nicks in their metal plating that can render them useless, other chemical processes can affect a CD's playability. Eleven years ago, thousands of compact discs in the UK reportedly became unplayable after they changed color from silver to gold in a process known as "bronzing," a reaction between the CD's lacquer and chemicals within the cardboard cases that housed them at the time. However, two months later, French-based CD manufacturer PDO said all affected discs had been made in the late 1980s at its plant in Blackburn, Lancashire, which had used a silver coating on its discs instead of the standard gold.
Other problems have become widespread, if not common. If the lacquer covering fails to evenly cover the disc's edge, air can penetrate and oxidize the aluminum. While such faults are relatively few and far between, their occurrence with a master residing on a CD could be costly. As CDs enter the realm of a cheaply made commodity, the best advice for professional users is to choose name brands and make multiple copies of every stage of a project.
