[alt-photo] Re: NuArc 26-1KS ideal vacuum pressure?

[Jeremy Moore]

I use ~9, but that's assuming my dial is accurate. Any higher than this
setting and I don't get any increase in sharpness so I've just left it
there. You should also be sure your emulsified paper/negative combo is
backed by something to help keep the moisture from being sucked out.

-jeremy-

On Tue, Apr 6, 2010 at 3:08 AM, Loris Medici <mail at loris.medici.name> wrote:

> Hi all.
>
> Yesterday, I finally managed to have my new NuArc 26-1KS installed. Pretty
> exiting, seeing the vacuum bed operate was a real eye opener; I will
> finally
> be able to make sharp prints sized 12x12" / 11x16.5" or 12x16". Plus, the
> light integrator is a real bliss.
>
> My question is, what is the ideal vacuum pressure for the following
> processes? (If the concept isn't a total nonsense, that is...)
>
> - Iron / iron-silver processes: Cyanotype, Vandyke / Argyrotype and
> Pt/pd...
> - Dichromated colloid processes: Gum Dichromate, Casein and Carbon...
>
> As we all already know, humidity level and/or maintaining an absolute
> minimum of humidity in the paper/emulsion is essential for making those
> processes work successfully. Therefore, I fear of using too much vacuum and
> to cause humidity escape from the paper/emulsion.
>
> I'm thinking something around 10 mmHg... ???
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