Crawley's FX-2, Glycin and Potasium Carbonate ????

Discussion in 'B&W: Film, Paper, Chemistry' started by BradS, Sep 1, 2006.

  1. BradS

    BradS Member

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    Why does FX-2 call for Potasium Carbonate instead of Sodium Carbonate? Could one substitute Sodium Carbonate for the Potasium Carbonate in the formula? At what ratio? and with what effect?


    TIA.
     
  2. Gerald Koch

    Gerald Koch Member

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    Not only does it call for potassium carbonate but potassium carbonate, sesquihydrate. The reason, given by Crawley in either the original BJ article or as a later note, is that the sesquihydate contains some potassium bicarbonate which acts as a buffer.

    However, there is a modification of unknown origin known as FX-2K which uses a B solution containing 97.5 g/l of sodium metaborate. This is said to produce somewhat smoother tonality with a slight loss of acutance.
     
  3. Lachlan Young

    Lachlan Young Member

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    I think FX-2K was a Bill Troop modification as was the suggestion that 75ml of solution A could be used with 75ml of a solution B made from 150g Kodalk in 1l of water with 30-60g of sodium chloride being added to the 1l of working solution.

    Hope this helps,

    Lachlan
     
  4. Tom Hoskinson

    Tom Hoskinson Member

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    Potassium Carbonate is more soluble than Sodium Carbonate so you can make a more concentrated stock solution with Potassium Carbonate.

    However, I use the Sodium Carbonate version and it works fine.

    The 1971 Dignan Newsletter published a sodium carbonate version of Crawley's FX-2.

    See the APUG Chemical Recipes: http://www.apug.org/forums/article.php?a=48
     
  5. jim appleyard

    jim appleyard Member

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    In my copy of "The Darkroom Cookbook", the FX-2 formula call for crystalline Pot. Carb.
    Is this the same as sesquihydrate? Sorry, I never did well in HS chemistry. :sad:
     
  6. BradS

    BradS Member

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    Thanks. The Kodalk idea is interesting - although I do not have Kodalk at hand either. It seems that solution B could, in this case be approximated with a solution of Borax and Lye - but, again in what poroportions? I think I asked this somewhere else...will go search.


    Will also give the Straight Sodium Carb formula recommended by Tom H. a go. How much base fog can be expected with this version?
     
  7. Gerald Koch

    Gerald Koch Member

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    Usually this is the reason for potassium salts being used rather than the sodium ones. However, in the case of FX-2 there is no solubility problem with the amount of carbonate needed in the developer. Potassium alkalies are somewhat more active than the sodium ones in photographic developers and this may be the reason why it was used in the original formula.
     
  8. Lachlan Young

    Lachlan Young Member

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    I seem to remember a comment that crystalline Potassium Carbonate had some degree of buffering - is this correct?

    Thanks,

    Lachlan
     
  9. Tom Hoskinson

    Tom Hoskinson Member

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    I believe Crawley published a concentrated FX-2 stock solution recipe in the BJPA that called out a rather large amount of Potassium Carbonate.

    In any event, I use the Dignan Sodium Carbonate Recipe (with no Pincryptol).

    I get excellent results (with Kodak TMAX, Ilford Delta and EFke) with low fog levels.
     
  10. Gerald Koch

    Gerald Koch Member

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    The amount of buffering would depend on the amount of potassium bicarbonate present. This would not be very large if the potassium carbonate is of reasonable purity.
     
  11. Lachlan Young

    Lachlan Young Member

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    Tom,
    What sort of development times do you get with the Efke films at 20C?

    Thanks,

    Lachlan
     
  12. BradS

    BradS Member

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    Tom, Gerald and Lachlan:

    Thanks Guys! This all helps - lots! Now, jkust need to get some Glycin.


    Oh, BTW: elsewhere on the 'net somebody has made the assertion that Metol was Glycin was basically the precursor to Metol and that Metol was superior. I took this with the usual dose of sketicism but...???? What of it? any ideas or further opinions on the matter?
     
  13. Tom Hoskinson

    Tom Hoskinson Member

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    I've had good results with the following variation on Ole's method:

    EFKE 100, 50 & 25 With FX-2, diluted 1:1 at 20deg. C, gentle agitation for the first minute, then stand for 20 minutes without agitation, followed by gentle agitation for 30 - 40 seconds, stand for 20 minutes without agitation, followed by gentle agitation for 30 - 40 seconds, stand for 20 minutes without agitation, total time about 60 minutes.

    I define gentle agitation in a small tank as gentle inversion of the tank while smoothly twisting or rotating it.
     
  14. Lachlan Young

    Lachlan Young Member

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    Thanks for the information! :smile:

    Lachlan
     
  15. Gerald Koch

    Gerald Koch Member

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    One reads the most outrageous drivel on the net.

    I am uncertain as to the meaning of "precursor to Metol", is this meant in a chronological sense or in some other manner.
     
  16. Neanderman

    Neanderman Member

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    Dignan FX-2 formula

    Does anyone have the Dignan formula handy? The above link doesn't work.
     
  17. PhotoJim

    PhotoJim Member

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    If that were true, Ansco 130 would be just another print developer, but it has a tonality unlike any other developer and a shelf life that beats every print developer I've ever used. Glycin is no metol.
     
  18. Neanderman

    Neanderman Member

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    Actually, both Metol and Glycin are derivatives of p-Aminophenol (aka the sole reducer in Rodinal). Or, said another way, p-Aminophenol is a precursor to both Metol and Glycin.

    Metol and Glycin were both 'discovered' in 1891, albeit by different people.

    Ed
     
  19. Tom Hoskinson

    Tom Hoskinson Member

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    Here is the FX-2 working solution formula that I am using. I got it directly from Patrick Dignan in 1970

    Metol...............................................0.25 gm
    Sodium Sulfite...................................3.5 gm
    Glycin..............................................0.75 gm
    Sodium Carbonate monohydrate............7 gm
    Water to make...................................1 liter
     
  20. gainer

    gainer Subscriber

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    Kodalk also has good buffering. The 14.5 grams sodium hydroxide + 69 grams borax decahydrate + 16.5 grams water are equivalent to 100 grams Kodalk, close enough for government work if not for PE.:tongue:
     
  21. Neanderman

    Neanderman Member

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    Thank you!

    Can I ask what films you've tried and if you have some starting development times? A group of us are getting ready to run some tests on some films.

    Ed
     
  22. Tom Hoskinson

    Tom Hoskinson Member

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    Ed I've tried TMax 100 TMAX 400 TMY with good results (I have not tried Kodak's new version ofTMY yet), Also EFKE 100, 50 & 25 With FX-2, diluted 1:1 at 20deg. C, gentle agitation for the first minute, then stand for 20 minutes without agitation, followed by gentle agitation for 30 - 40 seconds, stand for 20 minutes without agitation, followed by gentle agitation for 30 - 40 seconds, stand for 20 minutes without agitation, total development time about 60 minutes.

    I define gentle agitation in a small tank as gentle inversion of the tank while smoothly twisting or rotating it.