From: William Marsh (redcloud54@earthlink.net)
Date: 08/27/02-02:35:35 PM Z
Yes, as close to center as is possible, but just a visual positioning is
enough for 33rpm. In the industrial plate spinners, a much higher rpm
was used, so plates were clamped in place on a very accurate center,
much like a centrifuge.
Most phono turntables have a removeable center pin, at least in my
experience. It could always be sawed off, if necessary. After all,
it's not like you would ever want to use it for playing records after
this mistreatment.
I forgot: The "degreased" plate can also be spun and coated wet, the
photoemulsion replacing the water as it is spun on.
Bill
epona wrote:
>
> This may be a silly question, but I am assuming you place the plate dead
> center, right? Then what do you do about the pin in the center designed to
> hold the record in place?
>
> thx,
> Christine
>
> William Marsh wrote:
>
> > You might try placing the plate on a turntable from an old phonograph,
> > set on 33rpm (or slower). Turn on the turntable, pour on the emulsion
> > in the center of the spinning plate, stop pouring before it reaches the
> > edge of the plate. An amazingly flat even coating will be achieved.
> > You can then turn it off, allowing it to spin down by itself. If you
> > stop it abruptly you will get a wave of emulsion - a "hump" as it were -
> > across the plate. The turntable must be very level, and the plate must
> > be allowed to dry in place. If you move the plate before it dries, you
> > will affect the evenness of the coat.
> >
> > This should work for plates up to about 11x14 on 18 guage copper,
> > somewhat larger on lighter plates. The motors of turntables were not
> > designed for this, obviously, so weight of the plate, as you go larger,
> > becomes a problem. You might have to help the spinning get going on a
> > really big plate.
> >
> > Plate spinners were used in the printing industry for years, but now
> > with everything going digital, nobody uses them anymore. It could be
> > possible to find one at a graphic arts salvage place for a good price.
> >
> > One drawback is the emusion that is slung off during coating, but the
> > evenness you can achieve is amazing.
> >
> > Oh yeah, I forgot that it really helps if the plate has been
> > "de-greased" before coating. This allows even wetting over the entire
> > surface. In other words, if you run water over the plate, and the water
> > doesn't run off in a smooth sheet (if it "beads up"), then the plate
> > needs to be degreased: scrub the plate with alcohol, then rub the plate
> > with a mixture of water and pumice powder (hardware store) on a paper
> > towel or sponge. DON"T TOUCH THE SURFACE OF THE PLATE WITH YOUR
> > FINGERS, or you'll have to start over. When you rinse the plate, after
> > these treatments, the water should run off the plate in a sheet, no
> > beading up. Let it dry, then coat.
> >
> > Bill
> >
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