Acidification of Fabriano Artistico for Pt/Pd

Discussion in 'Alternative Processes' started by gattu marrudu, Apr 11, 2009.

  1. gattu marrudu

    gattu marrudu Member

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    Hi,
    I have found, from my little Pt/Pd printing experience, that Fabriano Artistico Natural White HP is my favorite paper for texture, tone, image quality and price.

    Still I have some problems with it - some times, the emulsion is grainy and too light, as if it came off by tiny chunks. I noticed this happens more when I coat with a Hake brush than when I use a synthetic wash.

    Could this be due to poor acidification?
    Dick Arentz suggests soaking the paper in a 1 to 2% solution for 3 min. In this forum, though, I read someone mentioning that they soak it in a 5% solution for 10 minutes. Won't this destroy the paper sizing?

    What I usually do is use a liter of solution and soak about 10 30x40cm sheets, putting them in one by one, rotating them from bottom to top and taking them out in the sequence I put them in - to ensure the soaking is as uniform as possible. I then discard the acid or use it to clear test strips.

    One more thing - after soaking the paper in the acid, I should NOT soak it in water - right?

    Thank you!
    gm
     
  2. Don12x20

    Don12x20 Member

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    Fabriano Aristico will require acidification.

    I use a 10% solution of Oxalic Acid (100g per liter), and brush coat this onto the paper. You can use your coating brush - there are no issues as long as you rinse it afterwards. I don't count drops -- just dip and coat until you have covered the surface. You will see little gas bubbles in places where a chunk of basic coating is neutralized. Just don't put so much on that oxallic acid is crystallized on the surface after drying.

    After coating the paper, hang and allow to dry. Keeps forever.

    There is no need to wash the paper subsequent to the acidification.
     
  3. gattu marrudu

    gattu marrudu Member

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    Thanks Don, I will test your method althought the concentration you use sounds very high.
    Would surface sizing help? And humidification?
    gm
     
  4. Don12x20

    Don12x20 Member

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    10% was the recommedation from Bostick-Sullivan when I received my paper. Works fine. They recommend 5% if you are going to soak.

    Surface sizing and humidification not necessary.
    I coat at about 60% humidity and don't humidify before exposure.
    YMMV
     
  5. Andrew O'Neill

    Andrew O'Neill Subscriber

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    This thread got me to thinking...I have a bottle of oxalic acid. So, I went down to my darkroom, made up a solution of 10% oxalic acid and brush it onto the paper that I use for Kallitype printing (Rising Stonehenge, which is acid-free).
    Let it dry, coated it with sensitizer and exposed it. Once it hit the developer (sodium citrate), it stained like hell, with weird orange colour lines running through it. Yuck.
    I mixed up a 5% solution and soaked a sheet of paper in it and this time it worked not too badly but I could see very subtle uneven densities...maybe I didn't soak the sheet long enough in the 5% solution. So another sheet in the solution and I gave it an hour soak. This time it worked really well. Blacker blacks and nice cool tone.
    I then tried putting drops of the 5% solution in with the sensitizer. Ten drops (mixed in with 22 drops each of the ferric oxalate and silver nitrate solutions for an 8x10). It worked, but seems slightly grainy compared to the print that received the oxalic acid bath for an hour.
     
  6. scootermm

    scootermm Subscriber

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    coating the paper with oxalic acid seems (to me at least) a very inconsistent means of acidifying paper such as Fabriano Artistico.

    The intent of an oxalic acid prebath is to neutralize the buffering agent used in paper making.
    Most are buffered with calcium carbonate.
    Coating the sheet of paper with a brush dipped in oxalic acid seems like it would inconsistently neutralize this buffering agent.
    I would highly recommend that you completely immerse the paper in a bath of 5% - 8% oxalic acid. My normal procedure with Fabriano Artistico (Extra White is the one I use).. is to pre-bath usually 20-40 sheets at a time.
    I cut the 22x30 sheets in half to make 15x22 sheets. In a large grout mixing tray I make up a big ol huge bath of 7.5% Oxalic acid. usually in the range of 8L +/- and then put each sheet in one by one until all 40 are in there. Then I'll usually shuffle from bottom to top a couple rounds (usually 4-5) then pull the out and hang them to dry.
    Makes for nice consistent results.
     
  7. PVia

    PVia Member

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    I put my Fab EW through 1% oxalic acid for 3 minutes...works great though some batches, I am told, need more occasionally. I refresh after 1-2 22x30 sheets of the 300gsm (140lb) variety. I rarely pre-acidify more than this...so far.
     
  8. Andrew O'Neill

    Andrew O'Neill Subscriber

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    That is exactly what I found, too.

    I'm now trying out a 1% bath. I think the secret to success is a long soaking time.
     
  9. Paul

    Paul Member

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    I have only brush coated once. I used a 10% solution of oxalic acid. When it dried, it left visible crystals on the paper. Not sure how to get around this, but maybe using less would have helped.
     
  10. Andrew O'Neill

    Andrew O'Neill Subscriber

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    What if you resoaked the paper in plain water?
     
  11. scootermm

    scootermm Subscriber

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    or just soak it in a bath of ox acid instead of brushing. ... or even in addition to brushing.
     
  12. PVia

    PVia Member

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    I use a low ox acid dilution bath because that's what Stan Klimek and Dick Arentz use...simple as that.

    If it works for the best...well...?
     
  13. photomc

    photomc Member

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    I use the soak as well, but a couple of tablespoons in a 2 liters of water - one sheet at a time (which is slow, but I can watch the paper to see when the bubbles stop). Takes longer, but it's my time - usually takes a couple of min and I am usually hanging the paper up, getting the next sheet ready - plus running a couple of trays with OA.

    Find what works best for you, everyone has there special way of processing - eye of newt, mis-matched socks, some funky hat while listening to Pink Floyd backwards :wink:
     
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  15. Kerik

    Kerik Member

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    You mean that's what they did when the latest edition of Dick's book was written? You may find that won't work so well on some batches of this paper. Always be ready and willing to modify your methods as papers are constantly changing. Stuart Melvin, Stan Klimek and I began using Fabriano Uno (the predecessor to AEW) for gum over platinum in 2000 or 2001. That's when we first started experimenting with ways to make Uno work better for pt/pd because it was such a great paper for gumover, but not so good for pt/pd by itself. We found oxalic acid to be the best trick. I'm pretty sure Dick didn't use this paper until after he saw some of our prints at APIS in 2003 or so...
     
  16. Don12x20

    Don12x20 Member

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    Well, not simple as that....

    Actually Dick recommends just brush or rod coating the oxallic acid. I've seen him do it a couple of times, as late as August 2007. He never mentioned soaking the paper in a bath in his masters workshop.

    And he recommends a simple pH pen, like the one he acquires from Light Impressions for testing papers (so it on the backside, unless you know for certain that something was put only on the frontside. (the surface texture is merely the surface hot-pressed or cold-pressed against. Sometimes a sizing is put on the front that you'd want to test).
     
  17. JBrunner

    JBrunner Moderator Staff Member Moderator

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    I just soak in diet sprite. (sprite zero)
     
  18. Andrew O'Neill

    Andrew O'Neill Subscriber

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    My test in a 1% bath of oxalic acid with a very long soak (about 2 hours) appears to have been successful. It's still in the wash though, and I won't know for certain until it has dried. It looks as though 1% will be fine for me, as it still delivers a nicer black.
     
  19. Andrew O'Neill

    Andrew O'Neill Subscriber

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    I should add that the paper I use is Rising Stonehenge...
     
  20. PVia

    PVia Member

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    Andrew...2 hours is a really long time. I'd be afraid that the internal sizing could break down...

    Kerik...Stan wrote an addendum/appendix in Dick's book, and that chapter has been the most helpful part of the book, for me that is. And as you so correctly point out, papers change all the time and the next batch may not react the same as the last. I know several printers who regularly use 8% or higher solution of OA to tame their papers.

    But, that being said, people who are just starting out need at least someplace to start, points of data that can help lead them to a method that will work for them repeatedly.

    So...are you still using Fab Uno/Traditional for pt/pd or have you been using EW? Curious minds want to know ;-)
     
  21. Kerik

    Kerik Member

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    Yes, I know that Stan wrote that section of Dick's book. Fabriano Uno was discontinued and replaced with Artistico Extra White a few years ago and I have used it for gumovers ever since. It's one instance where a new version of a paper is actually better than the paper it replaced! Even with acid treatment, Uno never gave me a straight pt/pd print that I was as happy with as papers like Platine and COT320. It was excellent for gumovers, though. I also use Rives BFK and Whatman's printmaking for gumovers, but I use them much less frequently than AEW because I usually prefer the smoother surface of AEW.
     
  22. gattu marrudu

    gattu marrudu Member

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    I am with scootermm and Andrew - brushing would probably just smear the stuff around and leave crystals due to the uneven coating action. Soaking, instead, would "wash out" the alkali in the whole sheet.
    I think it is important to soak all the sheets in the same bath, otherwise the last sheet would get a weaker bath.

    I tried soaking 20 30x40cm sheets in 4 liters of a 5% solution for about 30 minutes, until it stopped crackling (man, it does! Looks like frying shrimp!).
     
  23. Loris Medici

    Loris Medici Member

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    Why not hydrochloric (or acetic) instead of oxalic?

    Gattu, oxalic acid and calcium carbonate buffer will neutralize to calcium oxalate which is insoluble, therefore won't wash out. Yes, the paper will be neutralized indeed, but the neutralization product will remain in the paper.

    I just don't get why comparingly harder to obtain and more expensive oxalic acid (which the neutralizing product - calcium oxalate - stays in paper and gives a gritty surface, depending on how heavy was the buffer) is used for the purpose of neutralizing buffered paper, whereas easily obtainable and cheaper hydrochloric acid does the job (and that's with the added bonus: its neutralizing product - calcium chloride - is very soluble in water; it won't be there - unlike calcium oxalate - after the rinse!)... Maybe there's something about longevity (oxalic being better in terms of the keeping properties of the paper), but I couldn't find any info/comment/reference about this. I also absolutely couldn't find a reason why oxalic acid was chosen instead of hydrochloric acid? (Maybe because pt/pd printers are more likely to have oxalic on hands, since it's used to facilitate dissolution of ferric oxalate and/or to mix developer from raw materials and/or it's just safer to deal with oxalic acid -> but then there's acetic acid which also is safer to handle which the neutralization product is also highly soluble - calcium acetate...)

    Anyway, could be that it's not always the best to follow the best...
     
  24. Kerik

    Kerik Member

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    Here in the states oxalic acid is cheap and easy to get. I never get any discernible residue or gritty surface with my method (soaking, not brushing on). I'd rather have a safer powdered form of acid in my darkroom than a bottle of liquid HCl. I buy oxalic acid in relatively large quantities because I also use it to make potassium oxalate developer for a fraction the cost of buying potassium oxalate. Cheap, safe, effective, NO grittiness. The end.
     
  25. deisenlord

    deisenlord Member

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    What Kerik says. I have HCL around for etching prints but I rather not even have it in the darkroom.
     
  26. gattu marrudu

    gattu marrudu Member

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    How do you make potassium oxalate from oxalic acid? Here in EU it is very hard and expensive to find, compared to oxalic acid.