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

[ender100]

Francis,

It doesn't take a lot of vacuum to get a sharp print.  I usually use a setting of around 10 on the dial. I think what is more important for SOME processes is to let the vacuum run a while before exposing in order to get rid of tiny air bubbles.  For coated papers, this is not such a problem—but for some processes with slick tacky surfaces such as carbon, silver, POP, Photopolymer Gravure, a longer drawdown time before exposure helps.
--
Best Wishes,
Mark Nelson
http://www.PrecisionDigitalNegatives.com/
http://tech.groups.yahoo.com/group/PDNPrint/
http://www.markinelsonphoto.com/

On Apr 6, 2010, at 9:08:25 AM, "francis schanberger" <frangst at gmail.com> wrote:

From:   "francis schanberger" <frangst at gmail.com>
Subject:    [alt-photo] Re: NuArc 26-1KS ideal vacuum pressure?
Date:   April 6, 2010 9:08:25 AM CDT
To: "The alternative photographic processes mailing list" <alt-photo-process-list at lists.altphotolist.org>
Reply-To:   "The alternative photographic processes mailing list" <alt-photo-process-list at lists.altphotolist.org>

When I bought my NuArk 26-1K a few years back, the vacuum glass didn't make
it intact during shipping. Eventually I hope to replace it. Would anyone
using this model be kind enough to measure the glass dimensions including
thickness? What type of glass should I purchase to replace it? Tempered?

At the moment I am content using split back frames including my new 16 x 20
frame from Bostick and Sullivan with the rounded corners. The double hinges
allow me to print two separate negetives with different exposure times,
simultaneously without losing registration.

-francis

On Tue, Apr 6, 2010 at 9:23 AM, Jeremy Moore <jeremydmoore at gmail.com> wrote:

> 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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> >
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>



-- 
francis schanberger

www.frangst.com
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