I think I understand where the confusion is concerning laser and
photocopy toners and magnetism comes from.
In earlier times, these dry printers used two different powders, a
toner, and a "developer". The toner was made up of usually some
dye/pigment that made it black (such as carbon black, or many other
black substances) which was mixed with usually some type of very finely
ground styrene plastic.
The developer is where the confusion comes in.
The electrostatic drum was/is charged in such a manner to cause it to
attract this Styrene and pigment toner to certain areas which represent
black image on the final print, and to not have a charge that will draw
the toner to the drum in areas that are to be white.
The problem was how to get the toner "dust" onto the drum in just the
charged areas.
The system that was created involved using a very finely ground ceramic
and iron mix, which was referred to as "developer". The reason for the
iron was because there was a magnetic roller in the printer/copier,
which would become coated with this iron mixture, making it have a layer
of soft "fur" on it. The toner was mixed with this material so that the
coating of fur on the magnetic roller would have toner mixed into it.
This fur would stick out as iron tends to on a magnet, in close
proximity or even slightly touching the charged drum and the toner would
then jump to the image drum as required.
This developer was not a consumable (although some did end up being
fused to paper). It was simply a transfer method between the toner and
the image drum.
In an attempt to simplify and improve image quality, Canon came out with
a one step product, which was also embraced along with the Canon laser
printer engines, by HP. The toner and the magnetic "beads" were
integrated and made very small, so that the whole powder would jump onto
the image drum, and in effect, both toner an developer were used up
together and fused to the paper. These units also used a magnetic "fur"
roller, but since only one mixture was used and the developer was used
up at the same time as the toner, once the powder ran out, the
expendable were all gone and it was time for a new cartridge.
Some more recent printers/copies gave up on the magnetic roller and fur,
and went to a static charged roller, so only toner (nonmagnetic) was
required and it would jump from that roller to the image drum. Today
many manufacturers have gone this route, but if you have an older
machine, you will still require to use the magnetic formulations.
Art
Andrew said:
[This followup was posted to comp.periphs.printers and a copy was sent
to the cited author.]
In general can you tell if a toner is magnetic by bringing a bar
magnet next to the toner and seeing if it jumps to coat the magnet ?
I tried putting a permanent bar magnet next to some of the toner from
my Panasonic KX-P7100 printer, but no toner stuck to the magnet, so am
I safe in assuming it is not magnetic ?
Also, does this mean that the KX-P7100 doesn't use any magnetism at
all to coat the drum ?
I don't think most, if any, copier/laser printer uses magnetism,
except for some special ones maybe used for printing checks and similar.
Toner uses static electricity to stick to the drum. It is then
transferred to the paper, then heated and melted to be permanent.
A few 'how stuff works' links:
http://electronics.howstuffworks.com/photocopier.htm
http://computer.howstuffworks.com/laser-printer.htm
