U of S | Mailing List Archive | alt-photo-process-l | Re: muddy gum print--help?

Re: muddy gum print--help?

Charles, the first thing that strikes me is your gum mixture. If I understand correctly you mix your gum 1:1 with water. Are you mixing premixed liquid gum or gum powder? For gum bichromate I mix 1 part gum powder by volume to 2 parts water by volume. I then mix 1 part of this gum mixture with 1 part saturated pot dichromate and a small amount of pigment (tube w/c). Maybe your gum mixture is too heavy?

On Tue, Apr 14, 2009 at 3:10 PM, Charles Ryberg <cryberg@comcast.net> wrote:
       Thanks for the many helpful replies.  I've split my answer in two
parts--one about non-VOC size and this one about color balance.  This may be
more information than many of you want or need.
I use stock solutions of pigment.  The basic mix is 5 grams in 60 cc of a
50-50 gum/water mix.  That is, 30 cc gum, 30 cc water, 5 grams of watercolor
paint.  When I recently bought Fabriano Artistic paper from Artarama I
noticed a watercolor paint labeled Lukas Process Magenta which I ordered and
have used in the posted examples.  When I mixed this pigment at the above
concentration I got a very pale color--cheap paint, less pigment.  I settled
at 15 grams in 60 cc.  I won't use this paint after the tube is empty.  It
is labeled PR122 but the print is small and I may have written some other
number previously.
       When I was determining printing time and curves, the optimum mix was 3
droppers of my stock pigment, 2 of a 50/50 gum/water mix and 2 of saturated
potassium dichromate with an exposure of 2.5 minutes for cyan and 5 for
magenta.  The yellow drove me mad as I kept needing to increase exposure
time--past 10 minutes.  Thinking that ammonium dichromate was faster I
switched to ammonium for the yellow layer only and got a reasonable looking
curve at 5 minutes.  The problem with these figures is that they gave me
VERY dark and muddy prints.  I cut both the times and the concentrations by
10% then about 20% and got the image I posted--then carelessly ruined.
       My attempt yesterday was to reproduce the ruined print and see if a fourth
layer of cyan would help as Sam suggested.  Disobeying the fundamental rule
of one change per test, I also changed the printing order as suggested by
Joe.  Parallel with this print--that is, coat both sheets with the same
batch of mix, expose sequentially, develop together--I did a print with
spray starch.  I will write about that in my post on non-VOC size.  Both
these images are now posted at  http://ryberg.zoomshare.com/.
       The new image is clearly way too magenta.  There is pretty clear yellow in
the table cloth and the napkins are pretty clear white.  I will soon add a
layer of cyan and, depending on the results, maybe a layer of yellow.  If
there is any promise in the print, I'll reprint it with more yellow and less
       I'll worry about changing my triad of color when I get a print that isn't
Thanks for your time and help.  Charles     Portland Oregon