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This is to reference to the discussion about LASER Printerbuild
A short story of the Selenium Photo-sensitive Drum.
In the seventies, small Company offices saw the birth of thePhotocopier.
These used a Selenium coated drum, charged up to about3,000V(3Kv) by a
Corona wire near the drum. The rotating drum was exposed toa thin line
of light produced by a set of scanning mirrors and constantfocus lenses.
The areas exposed to light areas in the image, dischargesthe 3Kv charge
on the charged drum. This is called the Latent Image. Thedrum is immersed
In a liquid mixture of developer and toner, whereby thetoner is attracted to
Charged (un-exposed) areas on the drum. The drum now passesa 1,000 (1Kv) transfer corona wire behind the paper, transferring the latentimage to the surface of the paper. The final stage is to evaporate the cleardeveloper and fuse theToner, in the fusing heaters.
A major improvement was to add Arsenic to the Selenium Drum, improving
theDrum sensitive to blue colours (this is the reason thatforms and notes
were required to be filled-in and signed with black ink as a Blue signature "dissapears"!).
The next major improvement was the "Dry Copier",eliminating the
Stinky liquid developer. This of course led on to the modernLASER copier, this
still uses the Selenium / Arsenic drum but digital imagedetection, processing
and LASER drum scanning is used to produce the latent image.
This point also highlights the Drums lack of sensitivity to Blue /UV LASERS
A few tips when handling the drum
1) Selenium is EXTREMELY TOXIC!!!. Handle with gloves andmask.
Selenium in a heavy Metal and as such accumulates in thebody, similar
to Mercury. Effects may only become apparent Years later.
2) The drum surface is damaged by the sweat and oil fromfingerprints,
Use gloves.
3) In my years as a Photo-Copier Tech, small scratches onthe drum surface
were removed with a "steel-wool" type cotton basedcopper cleaner. The
Drum is lightly polished in an up and down motion from topto bottom.
Rinse with IPA(Iso-Propal Alcohol).
(DO NOT USE STEEL WOOL! this is for descriptive purposeonly). This
Process could only used 3 times before replacing the drum.
I hope these notes prove useful and informative to all,
Chester