Determine the basic exposure for palladium printing

Discussion in 'Alternative Processes' started by sudek, Sep 15, 2013.

  1. sudek

    sudek Member

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    The attached test strip was the one that I made for determining the basic exposure for palladium printing. I used a blank sheet of Pictorico Ultra Premium OHP Transparency Film to cover part of the coated area on Bergger COT-320. And It turned out that the area covered by the film would never reach the same density as the uncovered part, even if I had increased the exposure time up to 6 minutes. Its density was in gradual increase in brown, could not even reach dark brown, while the uncoverd part seemed to have reached its Dmax within 2 minutes.

    And for coating the paper, the suggestions I found on the net are telling that 6 drops of Ferric Oxalate plus 6 drops of Palladium solution would be sufficient for a 4X5 -inch image. I didn't realize that it was not sufficient until it turned out to be. What's the common practice in this situation? Let it dry down and give a second coating?

    Sorry for the naive questions as I'm all new to the process.

    Thanks much in advance for any kind reply!
     

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  2. Vaughn

    Vaughn Subscriber

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    Based on what I use for an 8x10 (~22 drops ferric/22 drops pt/pd on Cot320) , the amount you used seems sufficient.

    What light source are you using? 6 minutes does not seem long to me...my exposures are much longer with my LF negatives (more like 30 minutes) which tend to be very robust, but it is difficult to compare camera and digital negatives.

    I will let those more experienced with digital negs answer. Good luck in your explorations!

    Vaughn
     
  3. Rick A

    Rick A Subscriber

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  4. Loris Medici

    Loris Medici Member

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    Sudek buy a couple of 31 step tablets (from Stouffer - the T3110 variant - or PDN, I personally find the latter is better for our specific requirements...) and cover half of the tablet with the transparency material so that each step is half covered, and test again until you get at least two steps merged under the tablet + transparency, your standard exposure will be 1/3 stop less than what is needed to merge two steps under the tablet + transparency. (Because the test material UV density is about 1/3 stop ...) Standard Pictorico needs at least 2/3 stop more exposure IME. Therefore if you're getting black in 6 minutes w/o the negative material, you'll need *at least* 6 x ( 2 ^ (2 / 3)) ~= 9,5 minutes with Pictorico. (Probably a little more, I think Ultra is more opaque to UV...)
     
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  5. WetMogwai

    WetMogwai Member

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    Some papers and brushes are more absorbent than others. I usually use the same amount as you when I want to coat a 4x5 without going all the way to the edge, which is my usual way of coating paper. I'm using a 2" hake brush and Arches hot press. I add another drop of each if I want to coat all the way to the edge.
     
  6. sudek

    sudek Member

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    Vaughn: I used 8 black light tubes (30 watts each) and the distance between the tubes and the exposure plane is about 6 inches.

    Rick: Thanks much for the link!

    Loris: Thanks so much for the detail instruction!

    WetMogwai: Thanks much for sharing the experience. I'll look for a hake brush and have a try.


    Sorry for the late reply. I replied twice since the day before yesterday. But I don't know why it couldn't get approved to be posted. Not sure if it can be approved this time.
     
  7. sudek

    sudek Member

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    I've been trying to do more testing before resorting to step tablets and thus kept testing for longer exposure time, while shortenning the distance between the tubes and the print.

    Finally I shortened the distance to about 1.5 inches and exposed for 2.5 hours (see the attached, the right side covered by Pictorico Ultra Premium OHP Transparency Film). The result that it's still far from being dark is driving me crazy.

    Can anyone give me some advice? Would a step tablet make a difference? I really don't know what to do next. Longer time would lead to solarization, as what the four-hour strip showed. And isn't it unreasonable to expose a print for several hours?

    Thanks and sorry for my ugly brush strokes

    PS: The paper is Bergger COT320, prewet for ten seconds before coating. a Hake brush. 6 drops FO+6 drops of palladium solution for an image area of 4X5 inches.


    strip1.jpg
     
  8. Richardk550

    Richardk550 Member

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    Off-hand, it does not look like your paper is clearing very well, but it could be a number of other factors in the image - it may or may not be part of what you are seeing. A question: how old is your FeOx? I have been told it is good for six months, but only keep my FeOx three or four weeks.

    I do not prewet. I use sunlight and Pictorico and cannot relate to times with a UV box.
     
  9. Loris Medici

    Loris Medici Member

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    Hi sudek, what kind of lightsource do you use? Do you practice any other UVA sensitive process? (You can try with another process and see if it's exposing slow too - if yes, it's the lightsource / not chemistry.) Have you tried another paper? (Cheap Masa paper is very iron-process-friendly, try with another paper too, in order to rule out any problems with paper...) Pt/pd and hours of exposure doesn't seem right to me, especially so for materials like Pictorico... If you're Europe based see for Philips tubes ending with -05 or /05 suffix, these are perfect for UVA sensitive processes. (Output peaks between 360-370nm) Tube codes ending with -05-R or /05-R ending have in-tube reflectors; even better...

    P.S. Just for sake of comparison; my standart printing time with POP Pd under UVA tubes and 2mm glass is around 6-8 minutes, and (because of self masking) POP Pd is usually a little slower than develop out Pd.

    P.S.2. I don't understand what you mean by pre-wetting the paper? IME, COT 320 doesn't need any kind of special treatment...
     
  10. sudek

    sudek Member

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    Richardk550:

    You're right, it was not cleared enough. I just cleared this strip in Citrid Acid for five minutes. The result exhausted my patience to go through the complete procedure. Usually I would use Citrid Acid for the first bath, and EDTA+Sodium Sulfite for the second and third bath. Each bath five minutes respectively. But the problem is that the yellow stain would still be obvious even though I went them through the complete procedure.

    The FeOx has been three months old since I received it from B&S. I know it's a bit old. But it still seems to work well in the uncovered part.


    Loris:

    Thanks so much for the kind suggestion :smile:

    For pre-wetting the paper, I mean humidify the paper by holding it in the mist from a humidifier for few seconds. It's said to be helpful for reaching a deeper black, or so I have heard. :tongue:

    And there's one thing I can't understand. Should there be anything wrong with the paper, the solution, the tubes or the glasses, the part that was not covered by the Pictorico film shouldn't have reached its Dmax within 2 minutes in my first strip, and in totally dark too in the following strips with longer exposure time except for the four-hour one.
     
  11. Loris Medici

    Loris Medici Member

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    Ok, sorry, I forgot that you were having full dmax in 2 minutes - you've mentioned that in previous posts.

    The fact is that you can never reach the same dmax under the negative, more so with self masking processes, and develop out pd still has some print out, therefore some degree of self-masking. Most people aim for 90% of the dmax to calibrate for, that way you keep the dark tones more in the straight line of the H&D curve. There's always some amount of tonal progression, the trick is to find the point where the marginal utility equals 0. This is more easy to observe with a step tablet test; my method is to significantly overexpose the test tablet, then scan the print, average each step and use the threshold tool to find the minimum step number where it merges with the previous one and decrease the exposure according the numbers.

    Also, a too humid paper may compromise the negative, the silica coating is very very hygroscopic, will suck moisture and/or emulsion if it's not dry enough: try to not pre-humidify the paper or putting 1/2 mil impervious and transparent material (mylar for instance) between the paper and the negative.

    Regards,
    Loris.
     
  12. Richardk550

    Richardk550 Member

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    sudek:

    I use three baths of (4 heaping tbsp EDTA & 2 heaping tbsp of sodium sulfite per gallon) and get complete clearing - I no longer use citric acid at all & end up with the paper being the same color with no yellow stain left.

    Loris already covered my next comment: the Pictorico coating is water-soluble.
     
  13. Loris Medici

    Loris Medici Member

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    BTW, when not using a step tablet, you have to calculate the exposure individually for each step so that each one takes the same amount of "logarithmic" exposure, see below:

    1. Target total test exposure time: 10minutes,
    2. Each step: 1/3 stop, (pick your own values for these)

    then

    10:00 (start timer, none of the steps are covered)
    07:56 (cover the first step)
    06:18 (cover the second step)
    05:00 (so on...)
    03:58
    03:08
    02:30
    01:58
    01:34
    01:15
    01:00 (cover the 10th step, there should be one more step remaining, that will be exposed for the last minute...)

    To find the correct slices for a different total exposure and/or step resolution you can use the formulas below:

    1. To increase: time * (2 ^ (step)),
    2. To decrease: time / (2 ^ (step))

    Example:
    1. 10:00 + 1/3 stop = 10 * (2 ^ (1 / 3)) = 12,60 = 12:36,
    2. 10:00 - 1/3 stop = 10 / (2 ^ (1 / 3)) = 7,94 = 07:56

    Since that's a real PITA (both calculating and waiting before the exposure unit for an impractical and dangerous duration - UVA is not good for skin and eyes!!!), most people prefer using step tablets.

    Regards,
    Loris.
     
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  15. sudek

    sudek Member

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    Richardk550,

    Thanks much for the clearing experience:smile:


    Loris,

    Thanks a lot! Ok, I'll get a step tablet and have a try,but I'm wondering how I could make it in a few minutes with the step tablet while the blank pictorico itself couldn't get dark in more than two hours.
     
  16. Loris Medici

    Loris Medici Member

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    Hi sudek, try not-humidifiying the paper and putting 1 or 2 mil (25-50um) thin clear polyester between the coated paper and negative first. This became my standard practice after ruining a couple of negatives. The step tablet comes later when you figure out what happens right now.

    Edit: BTW, I reading again I see I've made a mistake, you don't cover the steps as I described above, you open them, I wrote the other way around above. You expose the first step 1 minute then open each step on each stated time. You must use a chronometer not timer (which counts backwards). Sorry for the inconvenience, it's long time I didn't it that way; step tablets makes people lazy! :smile: BTW, one plus of step tablets is that you have the same base for comparison with other tests and tests of other people...

    Good luck,
    Loris.
     
    Last edited by a moderator: Oct 2, 2013
  17. cliveh

    cliveh Subscriber

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    With the name of Sudek, may I ask what you think of your Sudek's work?
     
  18. cliveh

    cliveh Subscriber

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    Apologies for my last post, which doesn't make sense. What I meant to say was with a name like Sudek, what do you think of the work by josef Sudek?
     
  19. sudek

    sudek Member

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    Loris,thank you very much! I'll post the result later.

    cliveh,it's fine. I didn't feel offended. I like much his sensative and poetic way of seeing things. And above all, it's his great passion for photography and life that's impressive. I can't imagine how to operate a large format camera with just one hand and it's the left one.

    BTW, I adore much the works of his compatriot Josef Koudelka. The list of the photographers I love is very long: Hiroshi Sugimoto, Sally Mann, Richard Avedon, Ivring Penn, Eikoh Hosoe, Michael Kenna, André Kertész, H.C.Bresson,Sarah Moon, Paul Caponigro and many more...
     
  20. sudek

    sudek Member

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    I just got back to the experiment.

    Light: a bank of 8 30W HITACHI tubes about 4.5 inches above the print (the tubes are newly changed)
    Paper: Bergger COT-320
    a 21 steps tablet(I couldn't get the 31 steps tablet locally),half of which covered by Pictorico Ultra Premium OHP Transparency Film

    I exposed for 20 minutes and 40 minutes respectively, but the steps are all far from black,yes,even the part not covered by OHP film. Then I changed the glass from 5mm to 2mm and exposed for 40 minutes.Same result.

    Frankly speaking, it's making me feel despair. How come you can make it in just few minutes? I have no idea what I've done wrong. What should I do? To expose for two hours is not a good idea,right? I understand too long exposure is not right for making palladium prints.
     
  21. sudek

    sudek Member

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    step tablet.jpg

    The attached is the one exposed for 40 minutes with the 2mm glass.
     
  22. cowanw

    cowanw Member

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    Keeping in mind that this process will not give you as black a black as gelatine prints, your print looks pretty good. Increasing the contrast a bit will bring the blacks and whites in towards the centre a bit.
     
  23. Loris Medici

    Loris Medici Member

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    Can you please give more detail about your workflow (coating method, drying method times, developer, ect. all the details step by step) and working conditions (temperature, humidity)?

    The step tablet print you show us has no pure white and you can see tonal progression up to the 21th step. But you still don't have a full or almost full black.

    Interesting, never encountered such a case:
    - Lack of clear whites but full tonal progression until the last step indicates too much exposure to me. (I think we would agree on that.) If it was chemical fogging we wouldn't see tonal progression, right, only fog.
    - Lack of full back could be due some kind of bleeding, but then why it's only under the negatives? I'm totally puzzled.

    Have you tried other papers to eliminate if that's a paper issue? Also is your FO fresh?

    Regards,
    Loris.
     
  24. sudek

    sudek Member

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    Thanks much,Loris.
    The details are as belows:
    temperature:19 degrees, humidity: 68%
    I use a synthetic brush. After coating I let it dry naturally in the dark for twenty minutes.Then go for exposure. The developer is sodium citrate. Citrate acid and EDTA as clearing agent.

    I haven't tried other papers.The FO is not fresh though. I bought it from B&S about 5 months ago. How to judge if it dues to the freshness of FO? Also could it be the problem of UV lights? It's too cloudy these days to have it exposed in the sun.
     
  25. Loris Medici

    Loris Medici Member

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    What is the exact model number of your lights? Let's see if there's any spectral power distribution chart for them on-line...

    Definitely try other papers that are known to be working well with pt/pd process. Also old FO can be freshened by adding small amnt. strong hydrogen peroxide (strong to not dilute the iron solution too much), but that's not the business rigth now - we're not sure it's your FO, that (or buying new FO) would be the last measure.

    Regards,
    Loris.
     
  26. Loris Medici

    Loris Medici Member

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    BTW I see some grain only in the lower tones, usually sign of bleeding... Check if the print is bleeding during development. If yes try to use tween or similar surfactant to let the paper absorb the emulsion better...