Re: Bleach-development with gum
This is my best so far (after six test prints - including this one):
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
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
On 12/1/07 7:27 PM, "Katharine Thayer" <firstname.lastname@example.org> wrote:
> Loris, thanks for the report; I look forward to seeing your better
> 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.
> On Dec 1, 2007, at 9:02 AM, Loris Medici wrote:
>> 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
>> 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.
>> Quoting Katharine Thayer <email@example.com>:
>>> This isn't working very well for me; I don't know why. I've
>>> 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
>>> 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.