Pyrocat Mystery

Discussion in 'B&W: Film, Paper, Chemistry' started by CraigK, Dec 11, 2003.

  1. CraigK

    CraigK Member

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    Hi All,

    The other day I developed a roll of Tri-x (120) exposed at 320 and a roll of APX 100 (exposed at 80). I developed them in Pyrocat HD (1:1:100) for my usual time and temp. The negs ended up being quite thin. I put it down to having too many pints down at the local pub and underexposing as a result. Today however I developed another roll...this time HP5 (120) exposed at 200. The negs were even thinner than the others.

    The Pyrocat solutions A and B were mixed perhaps 5 months ago and are now in half empty bottles (separately of course).

    Is the developer losing potency?
     
  2. Eric Rose

    Eric Rose Subscriber

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    PyroCat does not keep well. Air will kill it quick. Time to make some more soup!
     
  3. sanking

    sanking Member

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    Craig,

    I recommend keeping the Stock A solution for no more than six months, but in fact in my conditions I have used it from partially full bottles after more than a year with good success. And when I did have a Stock A solution go bad, after about 2.5 years, it announced itself to me by turning a very dark brown.

    So in short I don't have an answer to your mystery question. But if the Stock A solution is clear I would look for other reasons for the thin negatives. Stock B, unless contaminated, should last for years and years.
     
  4. CraigK

    CraigK Member

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    Thank for the replies Sandy and Eric

    I will run a test tomorrow of two identically exposed sheets of film processed in different dev's (Pyrocat vc. D76)

    I will let you know how things turn out.
     
  5. CraigK

    CraigK Member

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    Well it looks like my Pyrocat HD has gone south on me. I shot two sheets of film and developed one in Pyrocat and the other in fresh D76. The Pyrocat neg was thinner than thin....barely there. The D76 neg was normal.

    The only thing I can think of is that my Pyrocat must have gotten contaminated somehow. So I dumped what was left of it (maybe 30 mls of each solution)

    Anyway I would like to order more from Photog Formulary or Artcraft. I am wondering however just how economical the kit for Photog Form is. Am I better off to buy the chemicals in bulk? I would like to get enough for 20 or 30 litres of working solution. What quantities of the chem's should I get if I go bulk?

    Thanks
     
  6. Donald Miller

    Donald Miller Member

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    I bought my chemicals in bulk from Artcraft. I have been mixing my own chemicals for some time for reasons of economy. I already had everything but the Cathecol and Phenidone A in stock so those were the only additions that I needed. I bought a pound of Cathecol and 250 gms of Phenidone. However that will make a lot more then the quantities that you specified.

    By looking at the formula at www.unblinkingeye.com you can determine what you will need in bulk to arrive at the your quantities. The only other consideration is a scale that will measure in gms. Good luck.
     
  7. philldresser

    philldresser Subscriber

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    Craig

    I have also bought from Artcraft and highly recommend them. They will supply any quantity required.
    I dont have access to a scale so they even batched the chems into packs capable of making 100ml of solution for me.

    Phill
     
  8. Michael Kadillak

    Michael Kadillak Member

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    Pyrocat HD maintains its strength for extended periods of time. Six months is a reasonable period if stored properly to expect it to perform as intended. Contamination is a serious problem that I have experienced first hand. I got some solution A into my solution B and it turned the B solution a tawny brown. I had to discard my B solution. As a result when mixing developer volumes, I use separate pipets and suction bulbs for each solution to take the contamination variable out of the equation.

    One of the variables that I believe many are taking lightly as evidenced by reports of thin negatives with Pyrocat HD is carefully measuring your developer temprature with a process or an accurate digital thermometer and adjusting your development time accordingly. If your developer tempratures are lower than expected and you develop for the time recommended for the higher temprature, you are taking a double adverse hit on the results. Just my $0.02.
     
  9. Tom Hoskinson

    Tom Hoskinson Member

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    Craig, it is likely that the phenidone in solution A has oxidized. When mixing the stock solutions and the working solution, it is important to use deionized or distilled water that has been boiled to remove dissolved oxygen.

    Other potential problems are the small quantity of phenidone required (with consequent measurement difficulties) and the difficulty encountered in dissoving it in water.

    I prefer to weigh the phenidone myself on a small electronic scale (about $30. on eBay) and dissolve it and the catechol in a small amount of dry methanol before adding them to the boiled water. Done this way, Solution A should last 6 months to a year.