U of S | Mailing List Archive | alt-photo-process-l | Re: was Miracle size for gum now tonal range

Re: was Miracle size for gum now tonal range

I don't think I told "I get a longer tonal range". What I told was: "I
use / prefer negatives with longer DR", adding now: -to get the tonal
range possible with the particular coating solution is able to give.
Tonal range (as I understand it) is a function of the pigment and
pigment concentration to my knowing.

The negatives I use are printed with a color that gives me 14-15 steps
with the 31-step tablet and 2A+1B trad. cyanotype (A being 20% and B
being 8%, I recently switched to A 25% and B 12% but haven't used
those negatives for gum yet. These need a more blocking color since
31-step table test prints indicate 16-17 steps...), therefore I assume
my coating solutions are compatible with a negative with a density
range of log 1.4.

Maybe gum spectral sensitivity is way different than cyanotype,
therefore the same negative (color) that reads log 1.4 for cyanotype
translates to a lower figure for gum - I can't tell since I haven't
checked that with a real (silver) negative. With gum, I left printing
step tablets very early, exactly when I discovered that my cyanotype
negatives are perfect for gum already. (My trials before - with lower
DR negatives - were all inferior in terms of shadow detail compared to
what I get with cyanotype negatives.) OTOH, I clearly remember posting
here a Stouffer 31-step tablet gum (thalo blue) test print showing 16
discernible steps (including dmax and paper white) a couple of years

BTW, I do get some color change in the darkest parts (blacks) of the
layer but not too much; it doesn't affect the midtones and highlights.
Does that counts as dichromate stain due overexposure?


2009/10/10 Christina Z. Anderson <zphoto@montana.net>:
> ...
> You say that with weaker di and greater exposure you are getting a longer
> tonal range--do you have a picture on the web of that comparison somewhere?
> ...