Pyrocat-PC, from Dixactol and stand development.

Discussion in 'B&W: Film, Paper, Chemistry' started by sanking, May 29, 2007.

  1. sanking

    sanking Member

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    In the Dixactol and stand development thread a reference was made to Pyrocat-P. I started to respond there, but decided it would be more appropriate to start a new thread.

    If you like Pyrocat-P you might be interested in Pyrocat-PC, which is is very similar, but the Stock A solution is mixed in propylene glycol rather than water for great shelf life, and with Pat Gainer's recommendation, uses ascorbic acid in place of sulfite.

    You can easily mix it yourself, as below.

    Pyrocat-PC
    Stock A
    Propylene Glycol at 150ºF 900ml
    pyrocatechin (catechol) 50 g
    Ascorbic acid 4.0g
    p-aminophenol 5.0g

    (Mix in the above order and stir until dissolved. Add glycol to 1000ml.)

    Stock B
    Distilled Water 750 ml
    Potassium carbonate 750g
    Stir until dissolved, then add distilled water to 1000ml

    Dilutions and development times same as Pyrocat-HD and Pyrocat-MC. Basically 1:1:100 for silver graded papers and 2:2:100 for alternative proceses. For semi-stand or extreme minimal development, 1.5:1: 200.


    (Mix in the order noted and stir until dissolved. This formula is easier to mix in glycol than either Pyrocat-HD or Pyrocat-MC).

    All of the Pyrocats give similar results to a number of pyrocatechin based proprietary developers, including Dixactol, Exactol Luz and Prescysol-EF. The advantage is that the Pyrocat formulas are public and you can mix your own for cost savings if that is desired. Like all of the Pyrocats, Pyrocat-PC gives very good results with stand and other forms of minimal agitation. So far as I know Pyrocat-PC is not available in kit so if interested you must mix it yourself.

    BTW, p-aminophenol is the same stuff used in Rodinal.


    Sandy King
     
    Last edited by a moderator: May 30, 2007
  2. Philippe-Georges

    Philippe-Georges Member

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    Sandy,

    As I am very interested in this pyrocatechin 'technology, I have some , presumably, stupid questions, but stupid questions can evolve smart answers...

    Can the p-amino-phenol be substituted by the easier to find para-cetamol?
    Is the Propylene Glycol only used to extend the shelf life, and if so, can it be omitted?

    Thank you for answering,

    Philippe
     
  3. juan

    juan Subscriber

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    I've been using the Pyrocat PC for about 3-months now. It is easy to mix - I heated the glycol in my microwave. I had previously used Pyrocat P and liked the way that it instantly turned purple when mixed, giving visual proof that the A and B solutions had been mixed properly. The PC version doesn't instantly turn purple - I find it turns a bit amber and slowly turns purple over several minutes time.

    I don't have any way to measure results other than by eye, but I seem to get some of the sharpness effects of minimal agitation development even though using continuous agitation (brush or PhotoTherm) with the PC version.

    Philippe, if I were going to mix in water rather than Propylene Glycol, I think I would stick with the original Pyrocat HD. I don't see much difference in the results of the two developers - the reason I mixed the PC was to try out the longer shelf life offered by the PG.
    juan
     
  4. sanking

    sanking Member

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    Philippe,

    I don't know about substituting para-cetamol. Maybe someone else can comment.

    If you want to mix in water try the original Pyrocat-P. Without the sulfite the stock solution probably would not be very long lived mixed in water.

    Sandy
     
  5. Tom Hoskinson

    Tom Hoskinson Member

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    In principal, Phillipe, you should be able to react paracetamol (Tylenol, etc.) with sodium Hydroxide and water to get rid of the acetyl group, leaving p-aminophenol Base.

    Check out this thread: http://www.f295.org/Pinholeforum/forum/Blah.pl?b-lab/m-1132019056/

    In the USA, we can buy p-aminophenol Base from Photographers Formulary.
     
  6. gainer

    gainer Subscriber

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    One could, of course, use ascorbic acid in place of sulfite even in the water mix. That might extend the life of the stock just by keeping the pH down until the B solution is added. It might also help sharpness and stain a tad if it's what they say about sulfite reducing those things. I haven't tried it myself, but it seems logical, as Spock would say.