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

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 yes
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. But
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...



From: Jim Larimer [mailto:jrlarimer@gmail.com] 
Sent: Monday, September 14, 2009 7:20 AM
To: 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 on
my face ;( 

On Sun, Sep 13, 2009 at 5:24 PM, Paul Viapiano <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
	When doing an exposure for the shadows, would you expect a much
shorter dev time?