Charles Steinmetz (csteinmetz@redneck.efga.org)
Fri, 12 Mar 1999 10:30:42 +0000
>I have something of a problem here. A renowned artist asked me if we
>could put an emulsion of some kind on a wall so that he could project a
>negative on that to get an image.
> - what kind of emulsion would work?
> - would that be DOP or POP
> - if DOP, how do you develop that
> - how do you calibrate the process
>
>Has this been done before?
Yes, actually, it has. Back in the late '30s and the '40s, machine shops
used to project full-size plans on the wall for big parts. During the War,
powdered silver emulsion was available in large sacks for the purpose. The
usual method of application was by spray (the packaged emulsion was dyed
blue so they could see it under the safelights). Processing was by sponge.
I've put photos on boulders using this method (although I coated with a
brush or foam roller).
The difficulty with spraying is that the sprayer needs to be silver-plated
to avoid contaminating the emulsion. Some stainless steels may be OK
without plating, but nickel- or chrome-plated brass is no good. If you buy
one of the liquid emulsions, you'll need to dilute it to spray it, and keep
the gun warm. You can probably dye it with blue food coloring, but check
to make sure the dye doesn't sensitize the emulsion to longer wavelengths.
Try it in miniature first, using the same projector and distance as the
real one.
Best regards,
Charles
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