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  1. #1
    m. dowdall's Avatar
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    Pyrocat B saturated solution

    I recently mixed up a batch of Pyrocat HD A and B solutions. I got the A solution right but not the B. I ended up with a lot of potassium carbonate that would not dissolve settle out in the bottom. Ya Ive got to check my scales when weighing out larger quantities. Its an older Mettler and it works great up to 10g. So any way now I have a saturated solution of potassium carbonate instead of 75g to 100ml of distilled water. The sheets that Ive developed in 2:2:100 my normal ratio, have come out fogged. They are not stained in the outside edges they just have reduced silver, that I can see. Ive tried a 2:1:100 solution and got reduced fog, but it was still present. After that long explanation my question is does any one know what a saturated of potassium carbonate is?

    E.G. Xg. of potassium carbonate to 100ml. distilled water.

    I'm looking to figure out what ratio of A to B to use.

    Thanks Michael

  2. #2
    gainer's Avatar
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    Quote Originally Posted by m. dowdall
    I recently mixed up a batch of Pyrocat HD A and B solutions. I got the A solution right but not the B. I ended up with a lot of potassium carbonate that would not dissolve settle out in the bottom. Ya Ive got to check my scales when weighing out larger quantities. Its an older Mettler and it works great up to 10g. So any way now I have a saturated solution of potassium carbonate instead of 75g to 100ml of distilled water. The sheets that Ive developed in 2:2:100 my normal ratio, have come out fogged. They are not stained in the outside edges they just have reduced silver, that I can see. Ive tried a 2:1:100 solution and got reduced fog, but it was still present. After that long explanation my question is does any one know what a saturated of potassium carbonate is?

    E.G. Xg. of potassium carbonate to 100ml. distilled water.

    I'm looking to figure out what ratio of A to B to use.

    Thanks Michael
    The Handbook of Physics and Chemistry says 112 grams of K2CO3 will dissolve in 100 ml cold water. It doesn't say what the final volume will be.
    Gadget Gainer

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    The original recipe for solution_B was 100g pot.carb to 100mL water making approx 130mL of solution. Sandy re-wrote it to make the made-up volume 100mL (75g pot.carb in whatever amount of water makes 100mL of solution). If you think you put too much pot.carb in the solution, according to Gainer's figure above you could only be a bit over what you're supposed to have, maybe about +10%. The cause of the fog looks to me like something else.

  4. #4

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    Quote Originally Posted by m. dowdall
    I recently mixed up a batch of Pyrocat HD A and B solutions. I got the A solution right but not the B. I ended up with a lot of potassium carbonate that would not dissolve settle out in the bottom. Ya Ive got to check my scales when weighing out larger quantities. Its an older Mettler and it works great up to 10g. So any way now I have a saturated solution of potassium carbonate instead of 75g to 100ml of distilled water. The sheets that Ive developed in 2:2:100 my normal ratio, have come out fogged. They are not stained in the outside edges they just have reduced silver, that I can see. Ive tried a 2:1:100 solution and got reduced fog, but it was still present. After that long explanation my question is does any one know what a saturated of potassium carbonate is?

    E.G. Xg. of potassium carbonate to 100ml. distilled water.

    I'm looking to figure out what ratio of A to B to use.

    Thanks Michael
    Michael, a few questions:

    What kind of film did you use?

    Did you measure the base + fog density of the developed film with a densitometer? If so, what was the density?

    Did you measure the base + fog density of the undeveloped film? This can be determined by fixing an exposed and undeveloped piece of film.

    What development agitation technique did you use?
    Tom Hoskinson
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  5. #5
    gainer's Avatar
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    Quote Originally Posted by john_s
    The original recipe for solution_B was 100g pot.carb to 100mL water making approx 130mL of solution. Sandy re-wrote it to make the made-up volume 100mL (75g pot.carb in whatever amount of water makes 100mL of solution). If you think you put too much pot.carb in the solution, according to Gainer's figure above you could only be a bit over what you're supposed to have, maybe about +10%. The cause of the fog looks to me like something else.
    Just to make sure the CRC people weren't lying, I weighed out 112 grams of K2CO3 into 100 ml of aqua pura. It took a while, but all dissolved and made a volume of about 130 ml. I agree, it's gotta be something else.
    Gadget Gainer

  6. #6
    m. dowdall's Avatar
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    Thanks to all for your replies.

    Tom, Ive gone back and checked the negs developed the week before from the same outing but developed in an older batch of Pyrocat. The edge fb+f of the older batch is Vis. channel .12, Blue channel .15. The ones form the new batch read Vis. channel .36, Blue channel .46. Developed in a home made slosher panel, agitation was 5 seconds every 30 seconds by lifting alternating sides. Film was Tri-x 4x5 from the same box.

    I assumed that it might be the solution B was the problem after searching this site and reading discussions about varying A and B ratios. Sandy King recommended not increasing the B over A, as it can cause fogging. But from what gainer and john_s say I have to agree that the B solution is not the problem.

    I also checked the chemicals and think my problem may be an old bottle of Potassium Bromide. Does anyone know if this stuff goes bad? The K,Br that went into A had a slight discolouration to the top layer. Grey? If this has gone bad then that surly is where the fog came from.

    Next weekend when I have another chance to get into the darkroom Ill make up another batch of solution A with some fresher K,Br that I should have used and try developing an unexposed sheet cut in two in each solution.

    Michael

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    Michael, making up a new batch of solution A with fresh KBr is a good idea IMO.

    With my sloshers (or cradles), I soak the film in tempered water for 5 minutes before developing. During development, I agitate very gently by slightly lifting alternate corners of the tray for 5 seconds every minute. That is my maximum agitation technique with Pyrocat-HD. Too much agitation can cause increased fog levels.
    Tom Hoskinson
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