Testing DVD writing drive

[Richard Pieri]

On Jun 15, 2009, at 11:48 AM, Laura Conrad wrote:
> It's the same batch I used for the recovery disks for my current
> laptop.  Do they go bad after a couple of years?


Recordable optical media can, yes, indeed, go bad.  At the heart of  
the matter is the organic dyes used in the recording layer.

Commercially pressed discs (CDs and DVDs) have pits of varying depths  
within the groove pressed directly into the metallic layer of the  
media.  The varying depths have different reflectivity values which  
translate to 0s and 1s.

CD-R, DVD-R and their cousins use organic dyes rather than a hard  
metallic layer.  The recording laser changes the phase of the dye  
where pressed discs would have pits.  Different phases have different  
reflectivity values; see previous paragraph.  The problem is that the  
dyes are organic, and they do decay.  How quickly depends on how well  
the dye layer is sealed within polycarbonate.  High quality media can  
last 10 years or more depending on storage conditions; cheap media can  
fail within 2 to 4 years.

That's not to say that your problem is media failure.  Try recording  
at a lower speed and see what happens.

For the record, not all recordable optical media use organic dyes.   
Magneto-optical (MO) media use a combination of higher-powered write  
lasers, metallic recording layers and magnetic fluxes to align atoms  
within the recording layer.  Different alignments have different  
reflectivity values; see previous.  MO media is far more durable than  
organic dye media; it is also more expensive.

--Rich P.