V
Vanguard
Okay, some more (oh my god, he ain't through yet). CD-R has a dye-based
recording layer that undergoes a phase change when heated to change its
reflectivity (i.e., the "pit"). Using a laser beam minimalizes the area
being changed so as to maximize capacity. Degaussing at any strength
will not directly affect that "pit" because degaussing doesn't cause
heat to the dye to make it undergo its phase change (i.e., degaussing
doesn't cause the reaction to change reflectivity) nor is it focused on
just that pit. That's why you don't have to worry about leaving your
optical discs next to old phones (with transformers for the bell),
underneath magnets, next to televisions, and such (but users often are
unaware that the foil is on TOP of the disc and not underneath).
However, optical discs are sensitive to heat which can degrade
reflectivity. So it is possible a strong and narrowly focused
degaussing path could physically stress the aluminum foil on the disc by
making it flex so that heat is generated which degrades the phase change
to spread it out and render the disc unreliable or unreadable. This
means the aluminum foil undergoes physical stress and that means it was
forced to flex to produce the heat. I hardly think that is good for the
glue that bonds the foil to the polycarbonate disc.
It is possible the heat from the mechanical stress can be limited to
reduce the harsh physical mistreatment to the foil. The laser heats the
substrate and foil to 250 C but it is highly localized heat and very
momentary. At this temperature, the recording dye melts away while the
substrate also melts and fills in the pit left in the recording dye
layer. A degaussing field is nowhere near as focused or tiny as a laser
beam, so it would have to force the aluminum foil to flex fast enough to
produce enough heat to force the phase change and effectively DESTROY
any use of the foil thereafter (i.e., it becomes one big "pit"). The
advertising for the unit you showed used "erase" incorrectly as it is
actually *destroying* the disc from further use.
CD-RW recording is slightly different. Rather than aluminum with a dye
recording layer, the CD-RW uses silver, indium, tellerium, and antimony
which has a polychyrstalline structure. The laser that is used during
the recording process heats a tiny "pit" to 500-700 C which melts the
shiny crystals in the heated spot into a dull non-crystalline amorphous
phase to lower its reflectivity. Annealing takes longer than writing.
Again, a strong magnetic field has no effect on the crystalline
structure. Erasing is accomplished by an "annealing" process that
heats the recording layer to 200 C which changes from the amorphous
(dull) state to the crystalline (shiny) state.
Trying to erase a recordable-only media using alternating magnetic
fields means destroying it (or severely reducing usability) since it
requires mechanically flexing the foil to produce the heat all over the
foil, and degauss paths are not as tightly confined as laser beams.
"Erasing" rerecordable media still means heat needs to be generated
since magnetism has no effect on the crystalline structure, and that
means the foil must be mechanically stressed to produce the heat. Since
the only way that degaussing can produce the heat needed to anneal the
CD-RW back to its crystalline state, or to flatten out the melting of
pits in CD-R, is to physically stress the foil (much like when you bend
sheet metal where the bend gets warmer as you repeatedly bend it there),
I doubt "erase" was used properly for advertising this device. More
likely it DESTROYS the media, but it probably doesn't do it fast enough
or localized enough to absolutely guarantee that the original "pits"
couldn't be detected as "ghosts" and so they also include the machining
off of the foil to utterly destroy any further use of that foil.
Since the unit isn't using laser or infrared beams to heat up the foil,
how would a degaussing field generate heat to cause the phase change in
the recording dye? Maybe by physically stressing the metallic foil by
making it flex repeatedly and at high rate but obviously that heat isn't
localized to the "pit" used to record the data. With CD-RW which uses
annealing, I suppose it is possible to monitor temperature (or know
through experimentationation to apply a known field strength at a known
cycle rate over a specific period of time) to heat the CD-RW to have it
anneal itself all over. That won't work with CD-R, however, since it
doesn't anneal. Since the device is to also erase magnetic media, it is
highly unlikely that it produces a sufficiently strong magnetic field to
physically distress the metallic foil use on optical media. If it was
strong enough to stress the foil on CDs, it would vibrate the rust right
off the tape media. It wouldn't be the first time that an advertisement
was written by marketing folks that don't have a clue as to how their
product actually works.
The point of that device isn't to salvage old used CD-R or CD-RW discs.
It is to destroy them. Because the OP was asking how to reformat
record-only media, it's a pretty good bet that he wanted to continue
using them afterward.
recording layer that undergoes a phase change when heated to change its
reflectivity (i.e., the "pit"). Using a laser beam minimalizes the area
being changed so as to maximize capacity. Degaussing at any strength
will not directly affect that "pit" because degaussing doesn't cause
heat to the dye to make it undergo its phase change (i.e., degaussing
doesn't cause the reaction to change reflectivity) nor is it focused on
just that pit. That's why you don't have to worry about leaving your
optical discs next to old phones (with transformers for the bell),
underneath magnets, next to televisions, and such (but users often are
unaware that the foil is on TOP of the disc and not underneath).
However, optical discs are sensitive to heat which can degrade
reflectivity. So it is possible a strong and narrowly focused
degaussing path could physically stress the aluminum foil on the disc by
making it flex so that heat is generated which degrades the phase change
to spread it out and render the disc unreliable or unreadable. This
means the aluminum foil undergoes physical stress and that means it was
forced to flex to produce the heat. I hardly think that is good for the
glue that bonds the foil to the polycarbonate disc.
It is possible the heat from the mechanical stress can be limited to
reduce the harsh physical mistreatment to the foil. The laser heats the
substrate and foil to 250 C but it is highly localized heat and very
momentary. At this temperature, the recording dye melts away while the
substrate also melts and fills in the pit left in the recording dye
layer. A degaussing field is nowhere near as focused or tiny as a laser
beam, so it would have to force the aluminum foil to flex fast enough to
produce enough heat to force the phase change and effectively DESTROY
any use of the foil thereafter (i.e., it becomes one big "pit"). The
advertising for the unit you showed used "erase" incorrectly as it is
actually *destroying* the disc from further use.
CD-RW recording is slightly different. Rather than aluminum with a dye
recording layer, the CD-RW uses silver, indium, tellerium, and antimony
which has a polychyrstalline structure. The laser that is used during
the recording process heats a tiny "pit" to 500-700 C which melts the
shiny crystals in the heated spot into a dull non-crystalline amorphous
phase to lower its reflectivity. Annealing takes longer than writing.
Again, a strong magnetic field has no effect on the crystalline
structure. Erasing is accomplished by an "annealing" process that
heats the recording layer to 200 C which changes from the amorphous
(dull) state to the crystalline (shiny) state.
Trying to erase a recordable-only media using alternating magnetic
fields means destroying it (or severely reducing usability) since it
requires mechanically flexing the foil to produce the heat all over the
foil, and degauss paths are not as tightly confined as laser beams.
"Erasing" rerecordable media still means heat needs to be generated
since magnetism has no effect on the crystalline structure, and that
means the foil must be mechanically stressed to produce the heat. Since
the only way that degaussing can produce the heat needed to anneal the
CD-RW back to its crystalline state, or to flatten out the melting of
pits in CD-R, is to physically stress the foil (much like when you bend
sheet metal where the bend gets warmer as you repeatedly bend it there),
I doubt "erase" was used properly for advertising this device. More
likely it DESTROYS the media, but it probably doesn't do it fast enough
or localized enough to absolutely guarantee that the original "pits"
couldn't be detected as "ghosts" and so they also include the machining
off of the foil to utterly destroy any further use of that foil.
Since the unit isn't using laser or infrared beams to heat up the foil,
how would a degaussing field generate heat to cause the phase change in
the recording dye? Maybe by physically stressing the metallic foil by
making it flex repeatedly and at high rate but obviously that heat isn't
localized to the "pit" used to record the data. With CD-RW which uses
annealing, I suppose it is possible to monitor temperature (or know
through experimentationation to apply a known field strength at a known
cycle rate over a specific period of time) to heat the CD-RW to have it
anneal itself all over. That won't work with CD-R, however, since it
doesn't anneal. Since the device is to also erase magnetic media, it is
highly unlikely that it produces a sufficiently strong magnetic field to
physically distress the metallic foil use on optical media. If it was
strong enough to stress the foil on CDs, it would vibrate the rust right
off the tape media. It wouldn't be the first time that an advertisement
was written by marketing folks that don't have a clue as to how their
product actually works.
The point of that device isn't to salvage old used CD-R or CD-RW discs.
It is to destroy them. Because the OP was asking how to reformat
record-only media, it's a pretty good bet that he wanted to continue
using them afterward.