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

[Loris Medici]

Hi Paul,

No, the emulsion is not solarizing (I observed the exposure
intermittently to make sure). The paper is still limp when I take it
out the frame, therefore it's not humidity loss. (Also, the back is
covered with thick black impermeable plastic stuff that came with the
unit.) I use 10 mmHg vacuum power.

18-21 for dop is longish, then I have to expect something even longer
with pop... (Bad news!)  But current tests indicate even 35minutes
won't be enough...

My usual gum exposures were 3-5 minutes range with 5% AD and UVBL bank
w/ very robust layers.

Thanks for the info,
I'll test the emulsions with my old lightsource, it's somewhere else
right now. Will test tomorrow with both the sun and old exposure unit
to make sure it's not my emulsions...

Regards,
Loris.


2010/5/14 Paul Viapiano <viapiano at pacbell.net>:
> ...
> 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.