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  1. #1

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    Eliminating 'Solarization' in Palladium Prints, Na2 vs Potassium Chloroplatinite?

    Hello All,

    After quite a bit of testing I continue to have difficulty printing a pure palladium emulsion without getting some appearance of what I believe is solarization (or pseudo solarization). It appears in the darkest part of the coating outside of the image area and looks like a water stain, for lack of a better description. It's not a huge deal, but I would like to resolve it if possible. I have confirmed an appropriate exposure time several times and have varied the amount of sensitizer I am laying down (currently 24/24 for 8x10), but to no avail. I have read that adding platinum to the mix should resolve this issue. I was wondering if both Na2 and the standard potassium chloroplatinite will work equally effectively for this purpose. Are there advantages or disadvantages to using one or the other? What percentages of platinum in the sensitizer are typically effective? Any feedback is greatly appreciated.

    Jeff
    Attached Thumbnails Attached Thumbnails Pd Scan.jpg  

  2. #2
    payral's Avatar
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    You really use a lot of emulsion - For my 8x10 prints I use between 12 and 14 drops of each (FO & Pd) - Most of my prints are pure palladium and if I use Na2 is just for a contrast increase. I print mostly on Arches Platine, some papers need a bit more solution somme a little less but never as 24/24.

  3. #3
    Ian Leake's Avatar
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    Solarisation/bronzing of palladium is caused by over-exposure to UV. Palladium is much more susceptible to this than platinum, but mixing them doesn't get rid of the problem (although the platinum may mask it to a certain extent). The only solution, AFAIK, is to reduce your exposure time.

  4. #4

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    Hi,
    Traditionally a small amount of a platinum salt was/is used to combat solorisation in palladium printing. It may be however that you are overdrying your coated paper. Try re-humidifying your paper before printing and see what happens (cheapest test first :-)
    HTH
    David
    What's wrong is wrong even if everyone does it. What's right is right even if nobody does it.

  5. #5

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    Hey Guys,

    Thanks for the replies.

    Philippe, I did initially begin printing with drop counts closer to what you are using... and come to think of it, I didn't have this problem. That was a couple of years ago though (with a couple of years break in between) and there are some significant differences with my workflow now that could also be (partly) responsible for the different results. For example, I was using the lithium palladium per Ron Reeder's workflow, so perhaps the co-salt affects this phenomenon. I haven't tried the LiPd since starting back up as I am currently shooting for the warm tones of the sodium palladium. I was also developing in ammonium citrate and am currently using potassium oxalate. I arrived at my current drop counts because I am constantly reading that the biggest mistake that beginners make is to not use sufficient sensitizer to coat. Additionally, I have read recommendations by seasoned practitioners like Arentz, who recommends 45-60 drops (total count) for an 8x10, and Kerik who recommends .5 drops per square inch of coating area, which works out to about 50 drops for an 8x10 (coated to 9x11). Conversely, I have also read that 'plating' can occur in the areas of heaviest coating, which is kind of how I interpret the results I am getting, but this contradicts advocates of a nice heavy coating. I know what a precarious process this can be and that everyone has their own way of working, so I will continue to work towards the results that I desire by trying to synthesize the information I read with my own practice. As for your response, your volumes and my previous experience are sufficient impetus for me to go back and run some tests with smaller drop counts.

    Ian, I have checked and rechecked my exposure time and am pretty confident that it is correct for my current workflow (which isn't exactly working so it's kind of a moot point =). I am exposing to a BLB array for 3:30. I suppose there is a possibility that if I have slightly thicker regions of coating at the edges of my coating area and this area exposes faster then it could be overexposing while my image exposure is right on. But with an exposure time of 3:30 I wouldn't think that it is grossly overexposing, which I believe is normally the case when solarization appears on a print. I will recalibrate exposure times when I test lower drop counts and see how that fares.

    David, I normally let the paper dry down about 15 min at 70-80F and 55-65% RH. I try to expose once the paper is dry enough that is will not stick to the negative. I recently tried force drying the paper with a hair dryer (warm setting to back of paper, cool to front) and then re-humidifying the paper prior to exposure. This produced much poorer results (lower DMax, increased plating) than I was getting with my normal workflow. I am however in the process of rigging together a humidity chamber for conditioning paper as a result of inadvertently running some tests at 70% and seeing an increase in DMax and a very slight reduction in the problem described originally. I knew that humidity was important of course, but I didn't realize what a difference a 5-10% shift could make in a final print. Perhaps more experimentation in the 70-75% range, combined with adjusting my drop count, will help shed some more light on this problem.

    Thanks again for all the constructive feedback,
    Jeff

  6. #6

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    Jeff, the area outside of the image area gets the most exposure, hence contributing to the results you're seeing. Basic exposure time should be judged according to that area, the 'base + fog' area of the negative. I mention this because there are several ways in which people test for basic exposure time. That is, unless the area outside of your image is receiving direct UV with no blank negative laying over it. This will vary depending on whether you're using analog negs or digital ones...

    If the problem exists outside the image area only, and you don't care about seeing brush marks in the borders, you can mask the perimeter with rubylith or red lithographers tape to eliminate them. Your clearing process must be very good (or use a dbl layer of tape or ruby) in order to avoid a grayness in that area.

    Another thing to try, that I swear by, is to sandwich the coated paper/negative combo between the contact frame glass and a piece of mylar in order to prevent loss of humidity through the back of the paper. This will also help dMax...

  7. #7

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    Pvia,

    I appreciate the reply. To be honest (dare I admit it here on APUG) I am printing with digital negs using Pictorico OHP Premium. The area shown in the attached pic was exposed through the Pictorico. I determine my exposure by the time at which additional exposure (through the OHP of course) will not yield additional print density. For example, with my current workflow I get increasing Dmax as I increase my exposure time to 3:30, exposing longer than 3:30 does not yield any increase in Dmax, so I set my exposure time to 3:30. I know this is somewhat of a departure from using a step wedge as some do, but the logic in it seems reasonable, no.

    I have considered masking the negs in computer by simply creating a black border around the image area, and I haven't completely ruled out this option. Despite my conservative coating technique I would still really prefer to show the coated area outside of the image, thus I am hoping to resolve the issue.

    I will give the mylar backing a shot. That combined with more rigorous humidification practices should at least make for a better print and hopefully help solve the issue.

    Thanks,
    Jeff

  8. #8

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    Jeff, good luck with that...hope it all works out.

    If, by any chance, this thread gets the axe, head on over to DPUG, where you'll be welcomed with open arms.

  9. #9

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    As to masking, my coating area is barely larger than the negative itself. I reuse matts with the window to the size of the negative. Place the matt on the paper to be coated, and coat to the edges. At the end of coating, I'll remove matt; and lightly brush the edges. It still gives the hand coating appearance while reducing the border area susceptible to solarization.
    van Huyck Photo
    "Progress is only a direction, and it's often the wrong direction"

  10. #10

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    Doug,

    I have seen prints that must have been coated in this manner - relatively narrow margins, while still having full coverage of the image area and retaining the distinct appearance of hand coating - and briefly wondered at the time about how precise the coat appeared yet, still had that hand coated aesthetic. Definitely food for thought. I have my humidity chamber tossed together and hope to put it to the test in the next day or two, I'll throw this coating technique into the mix to see if it helps. Thanks for the input.

    Jeff

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