Re: Fish Glue/Gum Arabic for Plate Bites

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From: Bill Marsh (redcloud54@earthlink.net)
Date: 03/29/03-01:56:10 AM Z


Joe,

Back in 1990, I used a manufactured plate-coating product to
make copper photoetching plates. It was a dichromate/orange
shellac-based liquid applied to the center of a spinning,
degreased, wet copper plate. The spin coated the plate
quite evenly, displacing the water. Let dry. Expose in a
platemaker with a halftone film positive. Develop with
water to wash away unexposed areas. Bake in a 500deg oven
until golden brown. Etch plate, with hardened coating, in
ferric chloride. Remove resist with ethanol. Ink it up and
print it!

I've been searching my archives to find you the address of
the company that makes it (or, "made" it), and searching
Thomas Register, where I originally found it, but no luck so
far. Old printers used to call it "hot top enamel" because
of the need to bake it to an effective resist hardness. It
was a widely used technique, because there was a whole line
of equipment designed around its use - plate spinners, for
example, that could spin a very large 16-18 gauge
copperplate at decent rpm. Personally, I used a discarded
phonograph turntable, which could handle a plate up to about
16x20, once you got it turning.

I'll keep looking, but my gut tells me that digital may have
wiped out this part of the old printing methods, along with
process cameras, and vacuum frames and such. It is quite
possible to make your own, however, using orange shellac
flakes (from furniture refinishing supply houses) and
dichromate, if you're willing to experiment. The results
are quite good, once you get the process down. Print it on
German Etching or Rives BFK, soaked in water for awhile, and
use alot of press pressure.

Regards,

Bill

Joe Tait wrote:
> Last night I exposed a copper sheet with dichro & gum arabic, with the intention
> of acid etching it as a positize to be a final piece. It adhered decently and I
> am going to harden it after work and hope for the best....
>
> Anyways, I learned recently that fish glue is the more traditional component to
> use for this application. I would like to do a lot of these. Could someone
> explain to me the dis/advantages to using one or the other?
>
> Thanks.
>
> -Joe
>


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