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Thread: Pyrocat HD mixing for the first time?

  1. #11

    Join Date
    Sep 1998
    Oregon and Austria

    Re: Pyrocat HD mixing for the first time?


    I agree with you wholeheartedly about doing things right, however, topping off when for mixing a developer like Pyrocat, PMK, or Jay's 510 Pyro, is simply not needed. What is important is consistency.

    If you standardize on, say, 500ml water (carefully measured out) with (for me) 10ml PMK solution B and 5 ml PMK solution A (also precisely measured out with syringes) to make 515ml of working solution, and if you test with this mix and calibrate EI and developing times to this mix, then, indeed, you have no need to top off and, as Jay observes, you have removed a step from the mixing. Just always do the same thing when mixing.

    I, and a whole lot of other careful photographers, mix developers this way, and I think the OP is safe with that method as well as long as he is consistent. On the other hand, if he chooses to top off, and remains consistent with that, then he'll be fine too.

    And, BTW, it is necessary to top off when making percentage solutions, since the dry chemical you add to the water will increase its volume somewhat. If you start with the final volume, you'll end up with too much after adding the chemical...



  2. #12
    jim landecker JimL's Avatar
    Join Date
    Sep 2004
    Vancouver, BC

    Re: Pyrocat HD mixing for the first time?

    Not to mention that my 1 liter pyrex beaker is marked +/- 5%, so I could have anywhere from 950ml to 1050ml when I fill it up...

  3. #13

    Join Date
    Aug 2000

    Re: Pyrocat HD mixing for the first time?

    No one has mentioned temperature. Pyrocat will work at 68 deg, but the times will be long. I believe the suggested temperature is 75 deg. F. Often on this site the complaints about thin negatives have been determined to be caused by low temperatures coupled with "suggested" times.

  4. #14

    Join Date
    Sep 2003
    Seattle, Washington

    Re: Pyrocat HD mixing for the first time?


    The advantage of not topping up is in simplifying the mixing. The advantage of topping up is in precision. Understanding the degree of precision required, or possible in any process, comes with experience. If one can't measure the precision in results, it's wasted effort, and simplification trumps precision. When teaching a concept, as in a high school chemistry class, these practical issues are not the point. Mixing and using a developer is a practical matter, where simplicity and consistency are more important than rote learning. Since I pointed out the error I was recommending, and my reasons for it, I don't feel I've led anyone too far astray. If you're more a letter of the law, than a spirit of the law kind of person, by all means top up, but your own error in recommending that topping up is not necessary when making a percentage solution illustrates the downside of rote learning compared to a fuller understanding of the underlying concepts that predict the consequences of deviating from standard practice.

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