are DVD disks very fragile??

[Ben Scott]

On Mon, Oct 19, 2009 at 2:40 PM, Lloyd Kvam <python at venix.com> wrote:
> I checked and found nearly 100 files with errors ...
> ... DVD+RW ... errors ... could not be fixed by rewriting the disk ...

  What do the surfaces of the disc look like?

  Any scratches on the "bottom" (shinny side) can skew the laser beam
as it travels through the outer layers to the recording medium.  Even
tiny scratches.  This is especially true when recording.  For reading,
there is error correcting information which can compensate for minor
scratches.  For recording, however, you're the one putting the error
correcting information there, so things are more sensitive.

  You can sometimes repair scratches on the "bottom", by "buffing them
out".  You essentially abrade away beyond the scratched depth, and
then polish the newly exposed surface.  They sell kits of varying
complexity and capability to assist with this.  Do this too much or
too often, and you'll go too far, of course.

  Scratches on the "top" (label side) are usually less perilous, as
the laser doesn't pass through the top side.  However, the recording
medium is actually closer to the top side.  A thick scratch on the top
side will damage the recording medium, and that can't be buffed out.

> I don't mind recreating install media when necessary, but would welcome
> any tips on care.

  There is an ancient and venerable text on the proper care of floppy
diskettes, faithfully reproduced here:

http://dcymbal.metabarn.com/ems/ems004.jpg

  Pretty much all the points still apply, except for the stuff on magnetism.

  Be aware that the inside of a car is usually subject to extremes in
temperature when there aren't humans inside to (turn on the heat|roll
down the windows).

-- Ben