#515: Dye, Dye My Darling

GETTING MORE TALE #515: Dye, Dye My Darling

Have you ever wondered how a CD-R burner works?

It’s quite complicated actually, but the basic idea is that data is encoded in binary “pits” and “land”.  If you recall your grade 10 math, binary allows you to record any data in ones and zeros.  In the CD world, this translates to “pits” and “land”.  Think of the pits as zeros, and the land as ones.  When you burn a CD at home, musical data is encoded with a laser.  The laser doesn’t actually etch the plastic or metal layers of a disc.  Instead, it burns the data into a layer of dye.  It is this dye that gives a blank CD its typical colours.  Once this information is properly encoded onto the blank CD, you can then play it on most household disc players.  But they don’t last forever.  The colour of the disc can be a clue how much life it has.  It can help indicate what dye was used in manufacturing.

  1. Cyanine dye (green)

These are the earliest blanks made, with a layer of dye that was also UV sensitive.  Unfortunately this meant that your CD could be destroyed by exposing it to direct sunlight.  The dyes were improved to make them more stable, but many people had their data destroyed simply by leaving the disc out, playing side up, where sunlight could get to it.

  1. Phthalocyanine (gold, silver, light green)

A more stable form of dye.  You’d have to leave your CD out in sunlight for two weeks to destroy it.  Unfortunately phthalocyanine dyes are more sensitive to the writing laser, and these discs required some technical advances to make for a good recording.

  1. Azo (dark blue)

Rated for a storage lifetime of decades.  More stable than the other two dyes.  It would take a month of sunlight to destroy an azo-based disc.  Also capable of faster writing speeds than other dyes.

Because it would have been easy to look at a green CD and say, “Nope, I’m not buying this one,” disc manufacturers tricked you by adding other colours to the dyes.   But the type of dye is only one factor in how good your CD sounds and how long it lasts.  A CD is like a sandwich made of plastic with layers in between where the data is stored.  Poorly manufactured CD-Rs allow moisture to seep in between the layers and destroy the disc.  And of course the quality of the burner is also critical to a good sounding CD-R.  And be careful if you’re labelling your disc with a marker.  Sometimes solvents from markers can react with the dyes.

In very rare cases, CDs and even DVDs have been known to explode during burning, according to a New York Times article from 2004.  It happened when a disc was spun too quickly, probably as a result of heat from the burning laser combined with centrifugal force.  This is why the upper limit for burning a CD is 56x.  Go faster than that and your music could go BOOM (and not in a good way).

A re-writable CD is different still from a dye-based CD-R.  A CD-RW (which can be re-written thousands of times) uses a metal alloy layer that is physically liquefied by the laser.  It’s crystalline before burning, but less reflective after burning.  Therefore a CD-RW has pits and lands made of more and less reflective spots on the disc.  And if you don’t like it, you can start all over again.  The laser re-heats the alloy, restoring it to its crystalline reflective state.

It’s all very technical and interesting, but how often do you record a CD today?   Though burning a CD will always be a pastime for many music fans, the majority have happily moved on to easier and quicker flash storage.  Is that as fascinating as a laser etching your music onto a disc?  No, but however you handle your music collection is up to you.

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25 comments

  1. Very interesting, I thought about the science behind CDs but never investigated it. Thanks for bringing it to light. I did have an interesting experience in burning a CD. I tried to burn 18 songs onto a disc I downloaded on Limewire. Three times, it would load between 6 and 8 songs and then it would close and say it was finished, very frustrating. Why did it do that?

    Liked by 1 person

        1. Well that’s a good deal on any day even if there are a few bad CDs in the batch. I have had plenty over the years, and from name brands too. Very irritating when I’ve been waiting for a CD for finishing burning and just before it’s done, it’s corrupted.

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  2. I’ve burned a bazillion CDr and DVDrs since I got my first computer in… 1997? I remember it had a CD burner and it was VERY EXPENSIVE. Must have been a Japanese import.

    Anyway, never thought about the science behind it, I just want it to work! So now I have more knowledge this morning than I did when I woke up, and that’s why I read up at Lebrain’s every morning, folks.

    As for today, I still burn a ton of discs. My car’s stereo system will read a CDr full of MP3s, but isn’t new enough to have an AUX jack for an MP3 player, so I dump stuff onto discs for the car.

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    1. Yes you were one of maybe two guys I knew who had burners in the old days. You and I had a long discussion about the 3 second gap between songs on live albums! Something you needed special software to eliminate, at the time!

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      1. Yeah the burner had its own software, but it was just a matter of selecting how long you wanted between songs. I usually left 1 second, to eliminate two songs crashing into each other. Songs with a fade-out you only had to wait 1 second, it was cool.

        Man, the first time I burned a disc… game changer.

        Liked by 1 person

  3. Oh! Most interesting, Mike. Actually had no idea how the whole CD burning thing worked, but my brain is nodding and telling me this all makes sense now. Thanks for that! Burned many a CD and always had issues burning at max speed on the old PC. None exploded, mind. Usually had to burn at x4 to prevent issues. Seriously slow. Sllllooooooowwww slow. Anyhoo, I put that down to the software/ hardware as opposed to the disc quality.

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      1. It used to eject the discs at the 80-ish% mark due to errors. Sometimes the successful discs were distorted sounding, too. The slow burning was pretty much the only way to guarantee a working disc!

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        1. I have dealt with sonic distortions too, and I really don’t know what caused them. One of my mix CDs has distortion right at the beginning of The Pretender by Foo Fighters.

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        2. It’s frustrating, huh? I can’t express how annoying it was to discover the distortion when playing the CDs back in the car for the first time (road music). I coulda smashed the dashboard!!

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