Mixing Pyrocat-HD From Scratch

Discussion in 'B&W: Film, Paper, Chemistry' started by Jim Moore, Nov 27, 2004.

  1. Jim Moore

    Jim Moore Member

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    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
     
  2. Ole

    Ole Moderator Staff Member Moderator

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    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!
     
  3. Jim Moore

    Jim Moore Member

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    Thanks Ole :tongue:

    Jim
     
  4. WarEaglemtn

    WarEaglemtn Member

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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. Alex Hawley

    Alex Hawley Member

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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.
     
  6. Jim Moore

    Jim Moore Member

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    Thanks Alex,

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

    Jim
     
  7. john_s

    john_s Subscriber

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    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. sanking

    sanking Member

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    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
     
  9. Jordan

    Jordan Member

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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. Tom Hoskinson

    Tom Hoskinson Member

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    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.
     
  11. sanking

    sanking Member

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    First, I have not had any problem getting the potassium bormide and sodium metabisulfite to go into solution in glycol, though it does involve heating the glycol to around 250º F. But at this temperature both go intoi solution quite easily.

    Tom is basically right in that the omission of potassium bromide and sodium metabisulfite does not make a lot of difference and may not be immediately apparent in your negatives. However, if you specifically test for it by running BTZS types testing in which test films are developed for different periods of time, and the results then read with a densitometer and plotted, you will indeed find some differences. The difference will probably not be evident with shorter development times but with the longer development times one would see with N+ development or with development for alternative printing the difference is quite obvious. In these cases the lack of potassium bromide results in slightly higher B+F levels and the lack of metabisulfite results in slightly more stain. This may not be important if you are using the 1:1:100 dilution and developing only for regular silver gelatin printing, but it definitely matters with the long development times we often need for alternative printing, where any differnce at all in the stain becomes very important because of the highly actinic nature of brown stain.

    I am currently working on some refinements of the Pyrocat-HD formula involving non-symmetrical mixtures of Solution A and B to make it more active for alternative printing and my current thinking is that the best place for the potassium bromide is in the Stock B solution rather than in the Stock A. So the next time I mix a new batch of Pyrocat-HD I plan to try to mix the bromide in with the Stock B, assuming it be soluble with the carbonate solution?

    As for the sodium metabisulfite I plan to continue to put it in the Stock A solution. Although it is not needed as a preservative in this solution, it nevertheless continue to have some impact on negative stain because it releases as sulfite when mixed with water and the sulfite, in even minute quantities, has an impact on total stain, especially evident with long development times.

    Sandy
     
  12. roteague

    roteague Member

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    Is is possible to purchase Pyrocat-HD in powder form? I have neither the time, nor inclination to mix chemicals myself.
     
  13. Jim Moore

    Jim Moore Member

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    You can get it in a liquid kit from Bostick & Sullivan

    http://www.bostick-sullivan.com/welcome.htm

    Jim
     
  14. roteague

    roteague Member

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    I couldn't find it in the product list. Are they using a different name for it?
     
  15. Jim Moore

    Jim Moore Member

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    They still must not have it listed. When I ordered it I had to call.

    Just give them a call and tell them you would like to order the liquid Pyrocat-HD kit and they'll know what you're talking about.

    Jim
     
  16. Jeremy

    Jeremy Member

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    It's listed after the rest of the pyro chemicals, so you'll have to go one page down from where you think it should be alphabetically: $29/50 quarts working solution. I bought some that should be here later this week.

    edit: here's a link, it's right at the top.
    http://bostick-sullivan.com/commerce/aa_41.htm
     
    Last edited by a moderator: Nov 30, 2004
  17. roteague

    roteague Member

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    Thanks Jim. I'll give them a call. I won't need it right away it looks like; I found out that because of all the humidity here, that all the negatives I have already shot are all sticking together. Ouch :sad: I've asked J&C about it, and he is asking the manufacturer, but I will probably have to chalk this up to a learning experience and reshoot. No big deal, I didn't shoot anything serious yet, just something to get my hand in doing B&W again.