[alt-photo] Re: NuArc 26-1KS problem (Slow printing times) / Cross-post, original @ apug.org

[Paul Viapiano]

Loris,

I'm glad you included times along with units, but as you may see from 
another thread here a few weeks ago, units are arbitrary because the NuArc 
can be calibrated many different ways. What matters most (to me) when 
comparing theses burners is times with a new bulb. That seems to get people 
in the ballpark for exposure comparisons.

So that being said, are you sure that the emulsion is not solarizing with 
long exposure, giving you an anemic dMax? Also, with long times, the vacuum 
frame draws a lot of moisture from the paper. Are you laying a large piece 
of mylar or other thin plastic on the bed before placing your negative 
sandwich? This will help keep the paper humidified. Isn't that a big factor 
in pop palladium? I also use a vacuum of about 15 pounds of pressure rather 
than let it rip all the way to 25 or 30. Don't know how much difference it 
could make as well.

I've found that my DOP palladium negatives need 7-8 minutes in the sun 
(bright, clear, So California sun), but 18-21 minutes in the burner (with a 
brand new bulb), so I'm crafting new negatives and curves to compensate.

I also see this in my gum printing with paper negs that normally print in 2 
minutes in the sun take 6 minutes in the burner.

I share your frustration. I thought that a burner would just be a drop-in 
replacement or get faster exposure times, but instead there is a lot of 
recalibrating etc in order to maintain what I consider decent workflow 
times.

Paul


----- Original Message ----- 
From: "Loris Medici" <mail at loris.medici.name>
To: "'The alternative photographic processes mailing list'" 
<alt-photo-process-list at lists.altphotolist.org>; 
<CarbronTransfer at yahoogroups.com>
Sent: Friday, May 14, 2010 12:59 AM
Subject: [alt-photo] NuArc 26-1KS problem (Slow printing times) / 
Cross-post,original @ apug.org


> Hi all,
>
> I purchased a brand new NuArc 26-1KS plate burner a couple of months ago,
> for the purpose printing with UV sensitive alternative processes.
>
> I've just had time to use/test it and I think there's something seriously
> wrong with the device; I currently struggle with pop palladium (Li2PdCl4 +
> AFO or Na2PdCl4 + AFO, noble metal solutions' concentration 0.52M, AFO
> concentration 1.05M), and the exposure times are incredibly long. 
> (Workplace
> conditions, 26C/77F 50% RH.)
>
> I was using a bank of UVBL tubes before (Philips 40W, /05 series - not
> manufactured anymore, replaced with /10 series recently), and my standard
> exposure time (with a 31-step tablet) was 6:30, giving me 28 distinct 
> steps
> including dmax and paper white.
>
> With the NuArc, I print for 900 units (17:15), and the step tablet test 
> says
> I still have to give 1 stop more exposure for being able to get 28 
> distinct
> steps, and more importantly I'm currently getting a pretty anemic result
> with low dmax. Awful. Something's wrong, WRONG!
>
> What is your usual pt/pd (or any other print out iron process) printing 
> time
> (not units, time!) with this unit? (Or, similar units?)
>
> What could cause the problem? I'm suspecting the bulb (NP-80) but it's a
> brand new unit and I just don't get how could a brand new bulb work that
> much slow? (The visible light illumination is pretty strong BTW.)
>
> TIA,
> Loris.
>
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