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  1. #21

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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!).

  2. #22

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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...

  3. #23
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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.
    Kerik Kouklis
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    www.kerik.com
    2014 Workshop Schedule Online

  4. #24

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

  5. #25

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    Quote Originally Posted by Kerik View Post
    I also use it to make potassium oxalate developer for a fraction the cost of buying potassium oxalate.
    How do you make potassium oxalate from oxalic acid? Here in EU it is very hard and expensive to find, compared to oxalic acid.

  6. #26
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    An excerpt from my workshop manual:

    To make potassium oxalate from raw materials:

    (You may want to do this outside or at least with good ventilation as the process gives off CO2, some heat and a significant amount of bubbles.)

    To make 2 Liters:

    1. Start with 1100 ml cold distilled water in a large container

    2. Add 450 grams of Potassium Carbonate mono with stirring until dissolved. This will cause the solution to heat up.

    3. SLOWLY add 400 gm of oxalic acid to the potassium carbonate solution with stirring, waiting each time you add the acid until bubbling stops. Continue until all of the oxalic acid has been added.

    4. Add water to bring total volume to 2 liters. Check the pH at this point. It should be near 7.0 (neutral). Now add more oxalic acid in small amounts and keep checking the pH. When you get the pH to about 6.0, you’re done.

    The pH of potassium oxalate is important. It should be used in an acidic state. This should be checked periodically with a pH meter or narrow-range pH paper. If the pH rises above 7.0 (i.e. alkaline) it can be adjusted by the addition of small amounts of oxalic acid. Add the oxalic acid powder a little at a time and keep rechecking the pH. I usually add oxalic until the pH reaches about 6.0. Filter your developer once in while and maintain the pH and you can use it for a very, very long time.
    Kerik Kouklis
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  7. #27

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    Great tip. Thanks a lot.

  8. #28

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    Kerik...

    Have you used the currently available Fabriano Traditional White for anything?

  9. #29

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    Hi Kerik,

    Diluted (non-fuming / safer than concentrated -> I don't advocate using or storing concentrated HCl at all! No need to buy concentrated form. I don't get why concentrated comes into your mind in the first place?) muriatic acid is as close as the nearest Home Depot (pool or garden sections) to ordinary US citizens (it's sold in any supermarket in Turkey for cleaning / "dissolving" calcium residue in the bathrooms and kitchen where the tap water is hard - does that ring bells? Calcium residue -> calcium buffer...) and would be definitely cheaper than buying oxalic acid from a chemicals supplier. No need pure grade; so called technical grade is OK. Also, a little goes a long time since it's further diluted (to final concentration of 1% to 5%). But I'm not in pennies and cents here...

    To me diluted (to safe levels) liquid acid is much safer than and easier to weight/operate compared to any powder. Powder can get airborne (and small particles can shed most easily), liquid does not.

    Grittiness is a fact to me since I've experienced this more than once, with more than one paper (all when coating with a glass rod). In any case I still think (and will tell people) that HCl or acetic acid (white vinegar) is definitely a better ("right") method for the purpose. My END.

    Philosophy of my objection: I don't like the idea of "if the best do it, it's OK for me too" kind line of thought, especially in the "alt" context. It would be better for the novice/less experienced practitioner to provide firm grounds to themselves why they are doing something in a particular way.

    Of course it's certainly understandable to prefer (and suggest) oxalic when one stocks and use it for other purposes too, moreso if they aren't experiencing any negative effects.

    Now, this sound like the infinite (and useless) discussion (somewhere else) about glyoxal against formalin against gluteraldehyde (in the context of hardening gelatin sizing)...

    BTW, I must add that I'm not questioning / discrediting anyone's (including yours) mastery, technical competence and technical / artistic talent here. I deeply admire your pt/pd and gumover pt/pd work and always drive my students to your website for a perfect demonstration of mastery... So don't take it personal.

    Regards,
    Loris.


    Quote Originally Posted by Kerik View Post
    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.
    Last edited by Loris Medici; 04-17-2009 at 12:58 PM. Click to view previous post history. Reason: (added the "glass rod" criteria)

  10. #30
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    Loris,

    I agree we are approaching the infinite and useless level of discussion, but I have one last shot from my end. Muriatic acid from the hardware store is usually about 37% dilution. I don't consider that dilute and I don't want it in my darkroom. I speak from experience that it is more hazardous to use and store than oxalic acid. Being a liquid, HCl is all to easy to spill and the airborne vapors from an HCl spill dwarf the hazard from oxalic acid powder in my opinion.

    You said: "I don't like the idea of "if the best do it, it's OK for me too" kind line of thought,"

    Ummmm, me either!! Did I say I was "the best" or do things the way "the best" do? I'm just passing on my experiences having printed pt/pd for nearly 20 years now.

    I haven't coated pt/pd with a glass rod since I found the Richeson 9010 brushes many years ago.

    I'm not taking this personally and I appreciate your kind words about my work. Like you, I am just presenting my thoughts on the "right" way to do this.
    Kerik Kouklis
    Platinum/Gum/Collodion
    www.kerik.com
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