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  1. #1
    Jim Moore's Avatar
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    Mixing Pyrocat-HD From Scratch

    Since I have 70 or so 8x10 negatives to develop over the next several weeks I would like to mix up a large batch of part A and part B stock solutions.

    These directions from unblinking eye are for 100ml of stock solution.

    Stock Solution A
    Distilled Water (125 degrees F) . . . . . . . . 75 ml
    Sodium Metabisulfite. . . . . . . . . . . . . . . . . 1 g
    Pyrocatechin . . . . . . . . . . . . . . . . . . . . . . . 5 g
    Phenidone . . . . . . . . . . . . . . . . . . . . . . 0.2 g
    Potassium Bromide . . . . . . . . . . . . . . . . 0.2 g
    Water to make . . . . . . . . . . . . . . . . . . . 100 ml

    Stock Solution B
    Distilled Water . . . . . . . . . . . . . . . . . . . . 70 ml
    Potassium Carbonate . . . . . . . . . . . . . . 75 g
    Distilled water to make - - - - - - - - - - - - - 100 ml

    I would like to make 1000ml of stock.

    My question is do I just multiply everything by 10 or are there any other adjustments that need to be made.

    Thanks!

    Jim
    "You miss 100% of the shots you don't take"...Wayne Gretzky

  2. #2
    Ole
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    Quote Originally Posted by JMoore
    I would like to make 1000ml of stock.

    My question is do I just multiply everything by 10 or are there any other adjustments that need to be made.
    Yes, and no. Multiply everything by ten, and realise that you've just made enough stock solution for 100 liters of developer at 1:1:100!
    -- Ole Tjugen, Luddite Elitist
    Norway

  3. #3
    Jim Moore's Avatar
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    Quote Originally Posted by Ole
    Yes, and no. Multiply everything by ten, and realise that you've just made enough stock solution for 100 liters of developer at 1:1:100!

    Thanks Ole

    Jim
    "You miss 100% of the shots you don't take"...Wayne Gretzky

  4. #4

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    I generally mix a litre of stock A solution and mix the B only when I am going to process film. A litre of A allows me to have it on hand... it is the slowest to mix. The B mixed at the time of use makes it easy to do & works well. I usually use up the litre within a month or two. Having enough on hand helps make sure I can mix plenty of developer so I am not as tempted to skimp and use only the minimum amount per sheet. I have that safety margin of using more than the minimum & haven't had any underdeveloped negs. It also gives a safety margin with regards to oxidation as I am generally using open trays for 15 min to an hour.

  5. #5
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    Jim, I would stick with mixing one liter batches. As Ole alluded to, a little goes a long ways. Even if you use the 2:2:100 dilution, one liter stock = 50 liters working solution. Assuming 3 liters for a tray full, this gives you at least 16 printing sessions, which should be enough for 70 negs, assuming 6 negs per batch.

    Another thing, the Potassium Carbonate increases in volume as the water is mixed in, by at least 1.5. That is, 1 liter of water will increase to about 1.5 liters or more once the carbonate is stirred in. Therefore, make sure your container is large enough to handle this. If going for the one liter mix, I use a two liter container.
    Semper Fi & God Bless America
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  6. #6
    Jim Moore's Avatar
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    Quote Originally Posted by Alex Hawley
    Another thing, the Potassium Carbonate increases in volume as the water is mixed in, by at least 1.5. That is, 1 liter of water will increase to about 1.5 liters or more once the carbonate is stirred in. Therefore, make sure your container is large enough to handle this. If going for the one liter mix, I use a two liter container.
    Thanks Alex,

    I did not know this. And this sounds like something that is good to know

    Jim
    "You miss 100% of the shots you don't take"...Wayne Gretzky

  7. #7

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    Quote Originally Posted by Alex Hawley
    Another thing, the Potassium Carbonate increases in volume as the water is mixed in, by at least 1.5. That is, 1 liter of water will increase to about 1.5 liters or more once the carbonate is stirred in. Therefore, make sure your container is large enough to handle this. If going for the one liter mix, I use a two liter container.
    Taking the 1 Litre example, the original instructions were for 1Litre water plus 1kg potassium carbonate which made up more than 1 Litre of solution_B. Since this confused some of us, Sandy re-expressed it as 750g potassium carbonate in water to make 1 Litre of finished solution_B. Same concentration, just a different amount, and expressed in more conventional terminology (i.e....and water to make 1 Liter)

  8. #8

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    Quote Originally Posted by JMoore
    Since I have 70 or so 8x10 negatives to develop over the next several weeks I would like to mix up a large batch of part A and part B stock solutions.


    I would like to make 1000ml of stock.

    My question is do I just multiply everything by 10 or are there any other adjustments that need to be made.

    Thanks!

    Jim
    If you want to mix 1000ml of stock you would in fact just multiply the everything by 10 as you correctly surmise. However, as others have pointed out, 1000 ml of Stock A and B will give you a rather large amount of working solution, either 100 liters of 50 liters depending on how you dilute it. If you plan to use that much developer in less than a year, no problem as the stock solutions should easily last that long in partially full bottles.

    However, for that quantity you might also consider mixing Stock Solution A in propylene glycol instead of in distilled water because it will last virtually forever mixed with glycol. I have been mixing my own Pyrocat-HD
    Stock A solutions this way since early spring and highly recommend it because you will have a solution that will last for years and years with no change in performance. The only problem is that you have to heat the glycol to mix the stock solution. If you decide to do this, first heat the glycol to about 250º F and then mix in the pyrocatechin, potassium metabisulfite, and potassium bromide, and then let the solution cool down to about 150º or less and add the phenidone. Be very careful with the hot solution as glycol at 250º F can be very dangerous.

    Stock B, a 75% potassium carbonate solution, mixed with water, has an almost indefinite life span so it can be prepared as per the directions at unblinkingeye.com.

    Sandy

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    Sandy, do you have any problems getting the KBr and sodium metabisulfite into the hot glycol? I would think that the solubility of these two compounds in propylene glycol would be pretty low, even when hot.

  10. #10

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    Quote Originally Posted by Jordan
    Sandy, do you have any problems getting the KBr and sodium metabisulfite into the hot glycol? I would think that the solubility of these two compounds in propylene glycol would be pretty low, even when hot.
    I mix my Pyrocat-HD "A" solution in polyethylene glycol (PEG) and leave the KBr and sodium metabisulfite out. I just assumed these two components would be difficult to dissolve in PEG. BTW, the pyrocatechcol and phenidone dissolve in the PEG at temperatures between 140F and 160F.

    When I started mixing the A solution this way I then added the KBr (as a percentage solution) and sodium metabisulfite when I mixed the working developer. I have made tests with the films I am using with and without the KBr and sodium metabisulfite, and I can not see (or measure) any difference in the results.
    Tom Hoskinson
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