Re: Bleach-development with gum
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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