CD-Rs may not be all they’re cracked up to be for long-term archives — even for those who’ve never believed the life-time archive hype.
But an investigation by a Dutch personal computer magazine, PC Active, has shown that some CD-Rs are unreadable in as little as two years, because the dyes in the CD’s recording layer fade. These dyes replace the aluminium “pits” of a music CD or CD-Rom, and the laser uses that layer to distinguish 0s from 1s. When the CD is written, the writing laser “burns” the dye, which becomes dark, to represent a “1” while a “0” will be left blank so that if the dye fades, there’s no difference; it’s just a long string of nothing to the playback laser.
So have you already lost those irreplaceable pictures you committed to the silver disc? PC Active suggests we should forget CD-Rs as a durable medium, after its own testing found some with unreadable data after just two years. “Though they looked fine from the outside, they turned out to be completely useless,” wrote the technical editor Jeroen Horlings, who had tested 30 brands in 2001, left them in a dark cupboard for two years and then re-tested them in August 2003. Of the brands tested, 10 per cent showed ageing problems. And it wasn’t just Horlings. After seeing the results, shocked readers contacted the magazine with their experiences.
Similar dyes are used with write-once DVDs. Swell.