Archive media, what does that mean?
Will I be around for 300 years?
It’s an excellent question and more complicated then just the survival of the optical disc (or me
). Not only does a disc have to survive 300 years but the drive and operating system (OS) that could read the data. So archiving your data, be it pictures or documents, spreadsheets or your audio collection requires careful consideration.
There are two distinctively different coatings for the reflective layer on CD-R and DVD-R & DVD+R blank media. Silver and Gold. These are not colors but actual metals in silver and gold. Each has unique characteristics that effect the playback of the media. Silver has the highest reflectivity and tends to be less problematic in older drives. Gold coatings have slightly less reflectivity and can be difficult to playback in some players.
The reflective layer is how the laser reads the disc. As the laser light beams onto the surface of the CD or DVD it needs to reflect back at the pick-up which shows the variation of pits (or spots) on the disc. This is how your data is ‘read’. With recordable discs the pits are created by laser light that causes a change in the recordable dye. If the the reflective layer appears to be similar to the pit then the disc reader skips over the data causing an error in playback. Generally a silver reflective layer is the best surface to go with. However with archival type media the issue becomes oxidation. Silver oxidizes, gold does not.
Oxidation happens when air chemically reacts with the metal. So the silver surface that had the high reflective properties becomes far less reflective then the gold. To the point of being unreadable. Now the question of 300 years does not mean it takes 300 years for this to happen. It actually happens much faster. Depending on the manufacture of the disc and type of disc. CD-R and BD-R use a single layer of polycarbonate. DVD uses a sandwich with the dye and reflective layer in the center. Interestingly enough the DVD has the shortest life span because air can get into the sandwich fairly easily. It’s essentially “glued” together and any imperfections can allow air to get in (both the inner hub and outer disc area present an issue). Also air can slowly penetrate the polycarbonate at a higher rate then the disc coatings which are far more ‘dense’.
How fast can this happen? days, weeks, months. Several years. Far shorter then 300 years. So if you have important data you want to preserver then Gold surface media is the way to go. The premium manufacturers of Gold archival media is MAM-A and FTI (Falcon). MAM-A offers a wide range of gold surfaces in DVD and CD-R. Currently Falcon offers a product line in CD-R with the gold surface.
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