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.) > > > -- > To UNSUBSCRIBE, email to [EMAIL PROTECTED] > with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED] > -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
