U of S | Mailing List Archive | alt-photo-process-l | RE: gum negatives redux

RE: gum negatives redux

Hi Paul,

Yes half the dichromate would increase the contrast, just as I want for
shadow exposures -> I like nice open tones in the shadows, not mud...

Since I use half the dichromate, the natural consequence of this would be
incresing the exposure time since the coating solution is much less
sensitive compared to normal mixtures. If I don't, I have the same problem
as you have -> a layer that goes down to the drain after normal development.
And I really don't like to develop shorter than 20-30 minutes -> short
developed layers don't give me enough confidence somehow. (In case I need
another layer on top of it and maybe would like to intervente manually...)
1.5 - 2x is compared to normal exposure. I really don't have a highlight
exposure; only normal and shadow exposure.

BTW, I will change the normal exposure time (by 1/3 stop steps) depending on
image, purpose, layer, pigment load and color. Nothing scientific there,
just by feeling. It's really hard to get used to that "feeling" stuff after
long years of printing S/G or highly consistent iron processes... But you'll
arrive there, don't worry. Gum's like Zen!

Also, I'm never afraid of overexposing, thanks to Marek's "bleach
development" method -> if a layer doesn't develop nicely I convince with few
mililiters of bleach! ;) Works perfectly. Therefore, I always try to err on
the overexposure side instead of underexposure...



From: Paul Viapiano [mailto:viapiano@pacbell.net] 
Sent: Monday, September 14, 2009 8:32 AM
To: alt-photo-process-l@usask.ca
Subject: Re: gum negatives redux

Using half the dichromate would increase contrast, correct?
And you use 1.5-2x the highlight exposure?


----- Original Message ----- 
From: "Loris Medici" <mail@loris.medici.name <mailto:mail@loris.medici.name>
To: <alt-photo-process-l@usask.ca <mailto:alt-photo-process-l@usask.ca> >
Sent: Sunday, September 13, 2009 10:24 PM
Subject: RE: gum negatives redux

> I'm not them (Jim and Katharine) but my 2c would be:
> Was your coating solution for shadows very dark / heavily pigmented? If
> it could be that you need a longer exposure indeed; since as I know it
> pigment amnt. will affect exposure time and contrast of the emulsion, so,
> what you're experience here is in line with gum principles and expected.
> if only you've a rather extreme coating solution there...
> BTW, FWIW, I usually use half the dichromate and 1.5-2x the exposure when
> exposing for shadows. Works better for me...
> Regards,
> Loris.
> ________________________________
> From: Jim Larimer [mailto:jrlarimer@gmail.com] 
> Sent: Monday, September 14, 2009 7:20 AM
> To: alt-photo-process-l@usask.ca <mailto:alt-photo-process-l@usask.ca> 
> Subject: Re: gum negatives redux
> Paul, my scientific answer is: Hmmmm? That usually works just fine, but
> then, last night I tried the same approach with the same results that you
> experienced! It may be that there is surfacing another variable in gum
> printing, bringing the number to 1243. Sorry, I have no answer, just egg
> my face ;( 
> Jim
> On Sun, Sep 13, 2009 at 5:24 PM, Paul Viapiano <viapiano@pacbell.net
<mailto:viapiano@pacbell.net> > wrote:
> Katharine & Jim...
> I tried the ivory black at 1 gram / 2 ml gum in a 1:1 ratio with the
> pot dichromate.
> Exposed for approx half my highlight exposure, but at 25 min in
> development, there was hardly any black pigment left on the print.
> I need to step-tablet this negative and try a few different
> pigments...but...
> When doing an exposure for the shadows, would you expect a much
> shorter dev time?
> Paul