[BlazingArizona]

All of my 15 year-old music CDs still play without a hitch, so I cannot believe the medium itself is fundamentally flawed.

The pits in a commercially produced CD are PRESSED, and will last until the substrate itself crumbles. The article is talking about CD's you make yourself ("burn") on chemical phase-change media.

[Kevin Curry]

That makes perfect sense.

[marlin]

the process for making cd roms and cd-r's is similar but different

but first a small primer - cd's are digital - meaning they are reading the functional equivalent of 1's and 0's - which in the case of cd's are called pits and lands

in a mass produced pressed cd a glass master is made of the original material to be produced - this is then made into a reverse negative stamp - which is put into the replication machine

in the replication machine the stamping process is done to a plastic disc - which is then coated with the relective layer - then coated with a lacquer - then silk screened with the label - then uv cured - the entire cycle takes about 4 seconds

for a cd-r the blank disc has 1 long spiral groove in it - it is then covered with an organic dye - typical cyanine, phtalocyanine or metalized azo - then with a lacquer coat - finally a printable cating may or may not be added

what happens over time with cd roms is that the normal atmospheric conditions allow water vapor to seap between the plastic layer and the lacqer layer and cause oxidation to occur - so dependent on your environment the process can take varying lengths of time

how the disc is read by the laser is that the cd reader is looking for the relflection delta - >70% - which changes the 1 to 0 or 0 to 1

the laser is reading straight up and down - so the angle is all important

when the cd rom starts oxidization the reflective surface no longer felects straight back - it aberates - which causes read errors

cd-rs use what is referred to as ablative technology - which is simply that the writing process fores a laser pulse which burns a whole in the dye layer - which is why it is called burning a cd - so that when the cd-r is then read by a reader the laser beam eith hits the organic layer and is absorbed - or goes through the burnt whole and reflects back - thus mimicing the pits and lands of the pressed cd

with a cd-r as the dye layer deteriorates the reflective delta changes and cases read error

also scratchs on the plastic side are not as catastrophic as cratches on the label side - as the lable side scratches can easily lead to either a scratch or a wrinkle in the reflective layer - which will cause read errors

of course gouges are a bad thing on either side