Re: CD writer wear out?
The rewritable media actually use phase change materials that are
locally melted by the write-laser. Depending on the shape of the
laser pulse, the material is left in either an amorphous or a poly
crystalline state (polycrystalline is more conductive and, hence,
more reflective.) The read senses changes in reflectivity. These
materials can be pretty unstable. I would be more careful about
heat (sat, in a hot car) than about normal room light.
Art Edwards
On Tue, Jul 18, 2006 at 09:10:43PM -0500, Owen Heisler wrote:
> On Tue, 2006-07-18 at 14:45 -0700, Cameron L. Spitzer wrote:
> > I make a lot of Knoppix disks because the Green Party here
> > gives them away. I get CD drives used or salvage or surplus,
> > all kinds and ages. Over time I collected nine drives that
> > stopped working: some wrote bad disks, others got read errors.
> > Took the cases off and cleaned the lenses carefully with
> > aqueous isopropyl "rubbing" alcohol on cotton swabs.
> > Eight of the nine work perfectly now. Try it.
> > The key is to remove the extra alcohol before it dries and
> > leaves a residue. Use a wet swab and then a dry one.
>
> Interesting. Now I know why I have been keeping those CD burners that
> work only half the time.
>
> > Note, even a perfectly good brand new CD-RW drive will write
> > bad CDs if you burn at full speed. The maximum writing speed
> > on modern CD blanks is very optimistic. Try burning at half
> > the automatically detected speed, or 16x, whichever is slower.
> > You will get a much higher yield. Your disks will be readable
> > in marginal drives that can not read disks burned at full speed.
>
> Before I learned this, I had some very annoying experiences with CDs!
>
> > Also, don't waste your time with CD-RW media. I have tried
> > several brands and none erases well. Second burn yield is
> > under 50%. Third burn is near zero.
>
> Just for the record, I have never bought CD-RWs, but I have collected a
> few (about 20) used ones. The ones I have can be written at max 4x
> speed, which is annoying. However, I have had very little trouble with
> them.
>
> I agree that they should not be used for any critical data. I use them
> only for testing/temporary burning. Isn't it called "stuck bits" that
> CD-RWs have after several burns?
>
> Oh, and supposedly CD-RWs will last much longer than regular CDs. Light
> causes the dye in regular CDs to deteriate, but that takes much longer
> with the dyes in CD-RWs. (Okay, now everyone can pick that apart...
> I've just "heard that" from someone.)
>
>
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