Philips has set up a telephone hotline to advise customers that if CDs have 'Made in the UK for PdO' near the label's centre, then they may be prone to tarnishing and become unplayable.
Philips pressing factory, PdO in Blackburn, Lancashire, produces a quarter of all CDs on sale in British shops. Each year 100 million-115 million discs are sold in the UK.
Philips admits it does not fully understand the process, but believes airborne sulphur is eating away at the nitrocellulose lacquer - it has now switched to an acrylic one - and then interacting with the CDs' silver coating to form metallic compounds. That causes dark bronzing of the reflective surface. Eventually, the CD player's laser cannot read the disc and will refuse to play it.
Philips has known for some time that PdO-made compact discs were prone to tarnishing. It had thought, however, that the problem extended only to singles packaged in sleeves made from poor-quality paper with a high sulphur content. It is now clear full-length discs packaged in plastic boxes are being affected too.
The Blackburn plant is unique in using silver coatings on its discs beneath the nitrocellulose layer. Other manufacturers use aluminium.
Philips believes the silver layer is more susceptible to sulphur damage. If the plastic box or paper booklet release sulphur traces those will eat through the protective layer.
Atmospheric sulphur, and storing CDs in hot or damp environments, may aggravate the problem, according to New Scientist magazine.
Dave Wilson, PdO marketing manager, is confident that the number affected is small. Philips has pledged that where possible, discs will be replaced.
The Philips/PdO telephone hotline is 0800 387063Reuse content