Burnt Discs appear different?

Discussion in 'Mac Basics and Help' started by Jschultz, Nov 26, 2006.

  1. Jschultz macrumors 6502a


    Mar 14, 2005
    Chicago, IL
    Is this true? How come I've never seen this?

    My girlfriend and I got in a fight because she swears up and down that when you burn a disc, the burnt disc has etches in it to show there is data and music on there.

    I simply laughed at her.

    The truth?
  2. CanadaRAM macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    The truth is you can definitely see a difference in colour / refraction on the burned area of the disc (the underside of course, not the label side)
    They aren't 'etches' per se, but they are microscopic spiral lines (working from the inside, out) where the dye inside the disk has been bubbled by the laser, creating the pits and lands that the laser reads as 0 s and 1 s. Angle the disk against the light and you can see the difference between Data and non burned areas (all data are ones and zeros, music, files, whatever). So, she's right.

    Commercially pressed disks use a completely different method, no dye, no burning. The aluminium reflective layer is impressed with the data pits all at one go as the disk is assembled, so commercial disks look quite different on the underside.

    Now: Listen up. View this as an opportunity. Admit you're wrong, aplogise for doubting her, praise her for being right, and let her make it up to you. I will leave you to work out the details ;)
  3. balamw Moderator


    Staff Member

    Aug 16, 2005
    New England
    I use this fact all the time to check whether an unlabeled disc has data on it or not. It's much more obvious on some media than others, but you can usually tell quite clearly. Works with some pressed discs too.

    A prostrate apology seems in order. :p

  4. RedTomato macrumors 68040


    Mar 4, 2005
    .. London ..
    Yes, I can easily tell how much space a half used disc has on it - it's quite obvious.

    The burnt space starts from the centre out wards.

    I remember reading about people who could visually identify by sight what tune was on a vinyl record disc by looking the patterns of lands and groves.

    I've looked at a few CDs and sometimes you can see stripes in the burnt data, but I couldn't be bothered to try to work out what kind of data the stripes were.
  5. Mernak macrumors 6502

    Apr 9, 2006
    Kirkland, WA
    You go in a fight with her about that, wow.

    Most disks you can tell but depending on the manufacturer of the disk it may not be as evident as some, but chances are you can still see it. I have also noticed that CD-Rs are much easier to identify this way compared to CD-RWs.
  6. MikeTheC Guest


    Apr 26, 2004
    Gallifrey -- Capitol City, Prydonian Sector
    What I have found is that the silver-colored CD-Rs are very hard to see this on (though with patience it can be done). The purple, green, and blue ones are probably the easiest to see.

    Sorry, dude, but your G/F pwn3d you, totally.

    OTOH, if she's looking for a new boyfriend...
  7. dukebound85 macrumors P6


    Jul 17, 2005
    5045 feet above sea level
    you can easily tell. if theres data looks like a smaller darker circle in a lighter circle. i use this when i have unlabeled discs and want to know if i can burn stuff to them
  8. Grakkle macrumors 6502a


    Oct 6, 2006
    Tsk tsk.

    Yes, it's quite noticeable. The burned portion shows up very clearly on DVD-RWs especially, because of the darker colour I suppose.
  9. Westside guy macrumors 601

    Westside guy

    Oct 15, 2003
    The soggy side of the Pacific NW
    While this does work for home-burnt disks, it often isn't possible for professionally mastered CDs or DVDs.

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