Brown or Green FAC for VDB

Discussion in 'Alternative Processes' started by davido, Jan 5, 2007.

  1. davido

    davido Subscriber

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    I just came across an older thread in which Dana Sullivan was recommending the use of Brown Ferric Ammonium Citrate for VanDyke. According to Dana, the Brown version "extends the shelf life of the solution, eliminates the white precipitate, and produces an image with considerably better mid-tone separations and not the harsh contrasty look of the Green Ferric Ammonium Citrate version"
    This is the first I had heard of Brown FAC and I was wondering if others had compared the two and what they thought. Should I put in an order to B&S?

    cheers
    david
     
  2. Jim Noel

    Jim Noel Member

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    I have not tried the brown because I have not needed to order since I read this posting by Dana. However, I do plan to give it a try as I know Dana tests thoroughly prior to publishing information.
     
  3. Dana Sullivan

    Dana Sullivan Advertiser Advertiser

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    I am not exactly sure why the Vandyke solution made with the brown FAC acts the way it does. Howard Efner did extensive testing and found that he could increase the contrast and increase the D-max of the brown FAC version by adding drops of .25% oxalic acid solution. No effect was seen in the green version.

    I think this gives us several reasons to use it; superior image quality, longer shelf life, and the ability to control the contrast (and by proxy, the color) in a way not capable using the traditional formula.

    Ferric ammonium citrate is an ill-defined chemical, similar to the way Ferric Oxalate is ill-defined. Unlike a water molucule (H2O) or a sodium chloride (NaCl) molecule, which both have very well know and defined chemical formulas, ferric ammonium citrate has no single chemical formula.

    Brown FAC is 16.5%-18.5% iron content while green FAC is 14.5%-16% iron, so there's a very wide latitude as to what constitutes ferric ammonium citrate, anywhere from 14.5%-18.5% iron.

    If you allow Vandyke solution made with brown FAC to sit undisturbed for 2-3 weeks a brown layer of free iron settles to the bottom. Shake the solution up before each use and you won't have any problems. The iron is too fine for any of the filters I have and it doesn't cause any problems in the printing process, so I see no reason to try to remove it.

    Thanks for reading.
     
  4. Jim Noel

    Jim Noel Member

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    Kevin,
    Thanks for this very complete reply. Now I am really going to have to try it.
     
  5. Dana Sullivan

    Dana Sullivan Advertiser Advertiser

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    Kevin!? Hah!

    No, no, no. I'm the good looking one!
     
  6. davido

    davido Subscriber

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    Brown FAC formula

    Dana

    Does your Vandyke formula use the same ammount of Brown FAC than would green? I came across some info on Wikipedia which states that you have to double the amount of FAC if it is of the brown variety. I've received my order of brown FAC from B&S and just wanted to confirm the formula before mixing up a bottle.

    thanks
    david
     
  7. Ole

    Ole Moderator Staff Member Moderator

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    My first attempt with brown had too much iron - left rust stains all over. Next mix used 20% less than the "standard green mix", and is still good after 2 years. :smile:
     
  8. Dana Sullivan

    Dana Sullivan Advertiser Advertiser

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    The formula I used to use for VDB using Green FAC was:
    30g Silver Nitrate
    15g Tartaric Acid
    90g Green FAC

    Divide 700 ml of 130*F in two parts. Disolve Silver Nitrate in one beaker, FAC and Tartaric Acid in the other. Make sure both beakers are completely disolved, then combine. Add water to 800 ml.


    The current formula I use is:
    30g Silver Nitrate
    17.5g Tartaric Acid
    110g Brown FAC

    Makes 800ml, like above.

    The iron content of the Brown FAC is only 2-3% higher, so I'm surprised to hear about iron staining.
     
  9. davido

    davido Subscriber

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    thanks Dana for your formula.
    Ole, perhaps the Brown FAC prints need longer clearing and, thus, the staining? What is your typical clearing protocal Dana? Also, do you use double coating with the Brown FAC?

    david