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  1. #1

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    Hi,

    I am starting out in pt/pd printing. It seems I have managed to read too much information regarding this process and succeeded only in confusing myself. I will be getting the Arentz book, but this is all being shipped here to Australia together so I will not have the benefit of reading it before I order chemicals. This is where your knowledge is very helpful!

    My main concern is contrast control. It seems the best way to go is to use Potassium Dichromate in the dev? My questions are:

    Assuming I will be doing 4x5 for now, how much potassium oxalate should I order?

    How much potassium dichromate should I order, and in what ratio should I mix it with the dev for the various contrast levels?

    How does using potassium dichromate instead of ferric oxalate #2 affect your sensitizer mix? Ie. do I simply use more ferric oxalate #1?


    Thanks!

    Adam

  2. #2
    cjarvis's Avatar
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    Do yourself a huge favor and just get the 25ml kit from B&S to start, and wait to get the Arentz book, which IMHO places too much emphiasis on sensitometry...especially for beginnners.

  3. #3
    cjarvis's Avatar
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    emphiasis? Sheesh.

  4. #4

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    Adam, you will want at least 500 ml of PO solution to develop your 4x5, personally I would use at least 1 liter to 1 1/2 liter....you reuse PO so really might as well insure you get the print covered completely.

    The problem is that you will have to make at least 5 different solutions of PO/Pot Di to have enough contrast spread. I use solutions of PO at 30% so if you plan to do the same you will have to order 750 grams to make 5 different 1 liter solutions.

    I use a 10% solution of pot di to be added to the different "contrast" solutions of PO. The way I do it is 1 ml pot Di/200 ml PO for solution 1
    etc, etc....so for one liter this would be the amounts

    Developer 1 1ml PD/200 PO= 5ml of PD/1 liter of PO
    Developer 2 2ml " " = 10ml
    Developer 3 3ml = 15ml

    And so on...I am sure you get the idea.....

    You will have to determine a replenishment rate of the pot dichromate, IOW, after you use the developer certain number of times you will have to add more pot dichromate per 200 ml or you will start seeing a lowering of contrast.

    Yes, you use only ferric oxalate number 1. For example if your initial drop count was 6 drops of pt/pd, 3 drops of # 1 and 3 drops of #2 you would use instead 6 drops pt/pd and 6 drops of #1.

    I disagree with cjarvis, there is no such thing as "too" much sensitometry and testing when we are talking about pt/pd. If you follow Arentz, you will have a methodical approach to printing that will allow you to "guesstimate" printing times and contrast right from the first print which will result in significant savings.

  5. #5

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    Adam,

    While getting Dick's book is not a requirement, I somewhat consider it the 'bible' of platinum printing. When I first started out, it had all the steps necessary to get through the process. However, even more useful is the formulary aspect of the book, which has many use formulations and procedures that you can use in pt/pd, including the dichromate approach that you are asking about.

    There is no other book that I've seen that has all of this information compiled together into a single reference.

    FYI, Dick discusses using SODIUM dichromate in a 50% solution, not potassium dichromate, however, there has been some speculation whether they are all functionally identical. I think they may be, except that it is possible to get sodium dichromate into a much higher percentage solution than potassium, and likewise for ammonium.

    What's important is that you have the same amount of dichromate in the developer, and using saturated solutions, it will take more if you use potassium dichromate instead of sodium dichromate.

    Yes, Jorge, I'm back. I've decided to give it one more try.



    ---Michael

  6. #6
    cjarvis's Avatar
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    Pardon the mea culpa...my suggestion that Mr. Arentz places too much emphasis on sensitometry is based in the context of someone who "managed to read too much information regarding this process and succeeded only in confusing" himself. If reading another book seems like the thing to do, I'm all for it. There is indeed no such thing as too much information...except when using it to spend too much time theorizing and not enough time practicing.

    I'll stick to my suggestion, however. Buy a small kit, and learn the basics first. There is as much intuition and feeling involved in Pt/Pd printing as there is technicality. Good luck, and enjoy your adventure.

  7. #7

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    Adam,

    Many of the contributors to this forum have vastly more experience than I, but let me suggest that IMHO it's all about the negative, not about the chemistry. You would do much better (and retain a modicum of your net worth) if you matched your negatives to your chemistry, rather than trying to manipulate chemistry to help your negatives.
    Secondly, don't underestimate the paper. Start with Arches Platine or Rising Stonehenge and hand size it with gelatin. I started hand sizing two weeks ago when I came across an unsized paper, but I went back and sized all my other papers and reprinted with amazing results. I can now single coat AP with better results than when I double coated it before sizing. That's a cost saving!
    Good luck and have fun!

  8. #8

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    Quote Originally Posted by Deckled Edge
    Adam,

    Many of the contributors to this forum have vastly more experience than I, but let me suggest that IMHO it's all about the negative, not about the chemistry.
    Well, it may not be "all about the negative" but it is surely a lot about the negative, which is why I think that a sound understanding the sensitometry of negative making and print making will make your work a lot easier save youy both time and money.

    And I agree with Michael about the Dick Arentz book. Although some may object to the heavy dose of sensitometry I don't think there is any doubt but that it is the most compleete book on Pt/Pd printing out there. The book Carl Weese did with B&S is also a very good reference.

    BTW, Dick is currently in the final stages of a revisioni of his book and I think it should be coming out later this year. I did an appendix on UV light for the book and use quite a bit of sensitometry in comparing the results from different light sources.

    Sandy

  9. #9

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    In followup to Sandy's post, I wanted to add that the sensitometry in Dick's book is very useful, but it is almost completely missing from the chapters that a beginner will be using to make their first prints.

    This means that the step-by-step procedures that are detailed can be followed without much difficulty for even a non-technical photographer.

    Since Adam stated that he is a bit overcome with information, I suggest that he put on some blinders for a little while. Take one source of information (Dick's book, or another source with complete printing information) and a starter kit from B+S, and make some prints.

    After a while, expanding the options and printing sophistication can be done by pulling the blinders away a bit.

    For a beginner, I don't recommend the dichromate method of developer, because it is a bit too much infrastructure for someone who may decide that pt/pd is not what they want to do. Additionally, the additional precautions that are required (although fairly slight) are somewhat of a distraction for a beginner.

    Once a certain amount of printing comfort and competence has been established, it is an easy transition to the dichromate method and other more sophisticated printing approaches (double coating, paper testing, pH, etc.).


    ---Michael



 

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