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Thread: Pyrocat-HD

  1. #31

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    Quote Originally Posted by Donald Miller
    I don't find the stain being the same in these two methods of development to be all that unusual. As I look at it, the material that is capable of containing proportional stain is the gelatin of the film emulsion. The amount of gelatin has not increased or decreased in the methods. Thus it would seem that the potential is to contain a given degree of stain.

    Donald,

    However, HP5+ negatives developed in Pyrocat-HD 2:2:100 in trays have a lot less stain, for a given CI, than negatives developed in Jobo with fast rotary action, which clearly suggests that vigorous development and oxidation through air contact also play a role in staining, at least in non-image forming stain. I know this for a fact because I tested some negatives made by Clay Harmon using the two method of development. This fact, in the absence of other consderations, would have led me to believe that a negative developed completely submerged in the developer, with very limited agitation, would not experience the same level of oxidations, and would consequently have stained less.

    I don't have a clear idea at this point why the supposition appears to be false.

    Sandy

  2. #32
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    Sandy:

    I can't help but think that oxidation of the developer has something to do with staining. Anytime I pour out the spent developer from my Jobo and it is brownish-orange, then I can expect the negative to have quite a bit of visible staining, including some undesireable general staining.

    I am beginning to wonder if saying 'rotary development' may be a little too imprecise to describe what may be going on. It seems to me that if you develop a sheet of 7x17 film in a homemade tube with a 3 inch diameter, then the film will spend a lot less percentage of time exposed to the air than if you develop 5 sheets of 8x10 film in a jobo expert drum, which has a much larger radius. Developer volume would also be a factor here in determining the amount of time the film spends in the developer versus out of the developer.

    Yet another variable with the expert drums is the fact that they dribble developer like a water wheel and this would maximize the exposure of the developer to the air versus a single straight tube which would have more or less a fixed surface area of developer that is exposed to the air.

    I guess the real test of this for someone with patience would be to tray develop some identically exposed film tests, and time it so that one stayed completely submerged, one spent about 1/3 of the time being hoisted into the air, and the other about 2/3 of the total time not submerged. I am willing to bet that there would be some noticeable differences in the staining.

    If I could learn to develop in trays without scratching, I think I would probably end up doing that method, because it seems to me to provide the least general stain and the maximum image stain with most films. My jobo tests have certainly shown me that slowing the rotation speed is a big help, but rotary processed negatives still are not as 'clean' looking as the tray developed ones.

  3. #33

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    Quote Originally Posted by clay
    Sandy:

    I can't help but think that oxidation of the developer has something to do with staining. Anytime I pour out the spent developer from my Jobo and it is brownish-orange, then I can expect the negative to have quite a bit of visible staining, including some undesireable general staining.
    Clay,

    I definitely agree with you that a very great percentage of the b+f or non-image stain results from oxidation of the developer, and that more of it results from fast rotation. This can be controlled to considerable extent, as we have discusssed in the past, by adding extra sulfite to the working solution, if the additional b+f stain is a problem, as it certain can be with films such as Tmax 400, BPF, and to a slightly lesser extent TRI-X and HP5+. On the other hand films like FP4+, Delta 100 and 400 and Tmax 100 hardly develop any b+f stain at all, though they all develop some image stain to a varying degree.

    The curiosity for me is why a sheet of film developed in a tube completely covered with developer and never in contact with the air would develop any b+f stain at all, especially since there is so little agitatin during develoment. And yet with minimal agitation I am seeing about the same level of b+f for film developed this way as with film developed with rotary agitation, *assuming that the two films are developed to the same CI.*

    Sandy

  4. #34
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    Could part of the reason be the large time difference between the methods? The deciding factors may be the surface area exposed to the developer AND the amount of time. With stand developing, you are developing for what, maybe 3-4X the time you would normally use for rotary tubes? Maybe there is some sort of natural oxidation that occurs in the solution. Isn't that the reason that we store the solutions as an A+B solution instead of mixing it all together? Jorge, you're the chemist here. Wouldn't the alkali start some natural oxidation once it was mixed with part A?

  5. #35

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    Quote Originally Posted by sanking


    The curiosity for me is why a sheet of film developed in a tube completely covered with developer and never in contact with the air would develop any b+f stain at all, especially since there is so little agitatin during develoment.

    Sandy
    I meant to add to the above sentence the fact that when the developer is discarded after developing with the extrmeme minimal procededure there is almost no discoloration at all of the spent solution. The large amount of developer that is required to completely cover the film in a tube appears to almost entirely eliminate the discoloration I previously associated with oxidation. But with long development times there is still some b+f stain, even when the discarded developer has no apparent discoloration. This make me believe that there must be some other mechanism in play in addition to developer oxidation.

    Sandy

  6. #36

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    Quote Originally Posted by clay
    Could part of the reason be the large time difference between the methods? The deciding factors may be the surface area exposed to the developer AND the amount of time. With stand developing, you are developing for what, maybe 3-4X the time you would normally use for rotary tubes? Maybe there is some sort of natural oxidation that occurs in the solution. Isn't that the reason that we store the solutions as an A+B solution instead of mixing it all together? Jorge, you're the chemist here. Wouldn't the alkali start some natural oxidation once it was mixed with part A?
    Well, I am very confused by this thread as well as the one at Michael's forum. I always thought of stand development as a technique for lowering contrast, but Sandy and others are reporting full CI's with this technique.

    Every time we introduce oxigen in the mix, we will have oxidation and as you correctly pointed out this is why we keep the two solutions apart, yet it seems Sandy is correct and there must me another mechanism. If I had to guess, I would say that the superadditivity mechanism is preventing developer oxidation, using all the available oxidation to regenerate the individual developing ingredients, thus the absence of discoloration in the solution. When we use robust agitation we are aereating both the film (with the left over developer on it) and the developer itself, and we get discoloration.

    I am doing some portraits tomorrow, so I will experiment with one of the negatives with this technique, but I dont know if I have the patience to sit for 40 min waiting for the film to develop.

  7. #37

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    BTW, with brush development I get little overall stain, for a .89 G bar I only get .25 b+f (UV), but then I think two factors are in play here, the film is always submerged and I use NaOH as the accelerator which requires a lower concentration to develop to the same CI as the Carbonate.

  8. #38

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    Quote Originally Posted by Jorge
    BTW, with brush development I get little overall stain, for a .89 G bar I only get .25 b+f (UV), but then I think two factors are in play here, the film is always submerged and I use NaOH as the accelerator which requires a lower concentration to develop to the same CI as the Carbonate.
    Jorge,

    The b+f of log 0.25 is with Ilford FP4+ (or Photowarehouse ASA125), right? And with UV reading?

    If so, this is fairly close to my own results with this film with regular Pyrocat-HD with the potassium carbonate accelerator.


    Sandy

  9. #39

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    Ah, sorry should have been more specific (I beleive this is twice I have done this to you.), the .25 is for TMY, for PhotoW I get somewhat higher, around .30 (UV) for high CI's. For low to moderate CI I get very low readings in the neighborhood of .12 to .18 (UV) for both films.

  10. #40

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    Quote Originally Posted by Jorge
    Ah, sorry should have been more specific (I beleive this is twice I have done this to you.), the .25 is for TMY, for PhotoW I get somewhat higher, around .30 (UV) for high CI's. For low to moderate CI I get very low readings in the neighborhood of .12 to .18 (UV) for both films.
    Jorge,

    Curious, I get much lower b+f with Ilford FP4+ than TMY.

    BTW, I spent the evening experimenting with a 25% sodium hydroxide B solution with Pyrocat-HD. I did tests at 1:1:100, 1:2:100, 2:1:100 and, 2:2:100, 4:1:100, and 4:4:100 4:1:100. I got the best results (in terms of maximum Dmax and minimum b+f) with the 2:1:100 dilution.

    I don't see much differnce, if any, in terms of minimum b+f density between the sodium hydroxide and potassium carbonate, at equivalent best amounts, but the sodium hydroxide sure works better in developing contrast quickly with the low contrast films. I think it is even more effeperhaps e than ABC Pyro at the 1:1:1: 7dilutiion, though for sure I will need to run more test to veify this.

    To balance the mixture at 1:1:100 I figure to adjust the Stock B Sodium Hyroxide solution to about 12%. Does that sound about right to you. I notice that your working solution is 1:1.5:100 with a 10% Stock B sodium hydroxide solution, which sounds very close to what I came up with as the best mix of the two stock solutions.

    Sandy

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