Re: Bleach-development with gum
Very cool.
On Dec 4, 2007, at 3:09 PM, Loris Medici wrote:
This is my best so far (after six test prints - including this one):
http://www.loris.medici.name/gum/bleach_2.jpg
I was testing with another negative with plenty detail / texture
but then I
decided to change the negative to make a fair comparison (portraits
are
harder since the tones are much more subtle).
Indeed, there's very very slight blotching / mottling when compared to
normal prints. In my case, I think this is mostly due uneven
coating. When
the coating is not too thin / thick and even, there's no perceptible
blotching / mottling. In this sample, the coating wasn't perfect. I
did
another before this one which was better, but I ruined it when I
tried to
coat it with polyurethane; eventually it wasn't dry enough and the
brush
awful marks on the print. (I have to learn to be patient!)
It must be noted that this print is not from a negative calibrated
for gum
specifically. It's from a negative (digital) calibrated for
Traditional
Cyanotype on Masa paper. So, probably there's still plenty of room for
improvement...
I would like to thank Marek for mentioning this method and
providing info
about his tests / procedure. This is a very nice method for those
who want
to make one-coat gums with a high dynamic range - especially for
images with
plenty detail and texture, less so when you need both high dynamic
range and
subtle tonality - but this is not where gum comes into my mind in
the first
place anyway...
Regards,
Loris.
On 12/1/07 7:27 PM, "Katharine Thayer" <kthayer@pacifier.com> wrote:
Loris, thanks for the report; I look forward to seeing your better
results.
I am inclined to think that my poor results may be related to the
size/hardener, and possibly partly to the amount of dichromate. I
agree with Marek that my first mix (that produced the most mottled
print) made too thick a layer because it was so heavily pigmented,
but that wasn't true of the less pigmented mix, that also eventually
mottled after repeated exposure to the bleach. It's interesting to
me that such a strong bleach you're using doesn't just take the image
right off the paper.
I actually really liked something I was getting yesterday, a very
low-
key print reminiscent of Bill Jacobson's dark portraits. I pulled it
out too soon and it dried down too dark, but I may try that again to
see if I can get a similar effect to how it looked when wet. In
fact, I guess I could just put it back in the bleach and let it
develop farther.
kt
On Dec 1, 2007, at 9:02 AM, Loris Medici wrote:
Katharine,
I got much better results - but there's still plenty of room for
improvement methinks, will share them soon...
But, the bleach I use is 55% sodium hypochlorite, not 5% as yours
(many sodium hypochlorite based bleach brands in Turkey are 55%).
For bleach development, I use 2x the amount of pigment I would
normally use, I cut the dichromate to 1/2x (5%), and exposure is
around 3x (or 4x if I find the coating is on the thick side).
I use 20ml of 55% bleach per liter of water. I first rinse the
print to get rid of the dichromate then put into bleach for 1
minute (face down), then I put into development water for 10
minutes, then I evaluate the print and put into bleach for another
minute - if it acts in a lazy manner - and continue to develop in
water.
Actually I did a wonderful print yesterday but ruined it later
because I was a little bit impatient and pulled it early in
development (I should give it 5-10 minutes more) and when I left it
for drying (flat) I got serious stain (in form of bleeding).
I get best results on unsized paper. I get flaking with sized paper
- I don't know why!? I never managed to make an acceptable print on
sized paper (both 3% and 6%, hardened with formalin) - kind of a
curse I guess...
Anyway, even if the results are very good considering they're one-
coat gums, their Dmax is still less than what I get from properly
done 3-coats... Will try harder.
Regards,
Loris.
Quoting Katharine Thayer <kthayer@pacifier.com>:
This isn't working very well for me; I don't know why. I've
posted
a couple examples from an afternoon's efforts.
The main dilemma seems to be that if I leave the print in the
bleach
for longer periods of time (10-15 minutes) I get blotching and
mottling of the image, (both with highly pigmented and normally
pigmented mixes of lamp black) but if I soak it in the bleach for
shorter periods of time (1-5 minutes) then development is too slow
for
my patience. Perhaps I've overexposed too much at 3x normal,
but I
wouldn't have thought so. The bleach I'm using is Western Family
brand; ingredients are listed only as Sodium hypochlorite 6%,
"Other
ingredients" 94%. I've used it diluted at 15ml/liter of
water. Gum
coating mix is, as always, 1 unit gum/pigment: 1 unit saturated
ammonium dichromate. Arches bright white paper, sized with
gelatin/glyoxal. I've included a normal print, for comparison.
http://www.pacifier.com/~kthayer/html/Bleachdev.html
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