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View Full Version : Uneven Pyrocat development - insufficient agitaton?



evanmoly
25-Feb-2017, 07:58
My example is roll film, but I believe the topic of sufficient agitation applies to all formats.

I processed 120 Neopan Acros with Pyrocat HD diluted 1:1:100 with roll film in a tank successfully several times, employing the inversion technique recommended by Sandy King at four intervals throughout the development time. I was happy with the tones.

I changed my agitation method to 'swirling' instead of inverting the last time i processed. I was using a much larger/longer tank than usual and was concerned that the higher volume of liquid sloshing around would lead to over-agitation.

The result of the swirling method was apparently uneven development most apparent in the highlights of some frames, over the whole image in others, and not apparent whatsoever in a most of the frames.

What confuses me is that some of the tones are great across the negative, while others from the same roll/similar lighting conditions are horrible. Is the swirling technique that inconsistent that some frames will develop evenly while adjacent frames do not?

Attached are a heavily affected frame, a partially affected frame and an unaffected one.

aflc
25-Feb-2017, 08:07
Stick to inversions as described by Sandy King. I've found that with pyrocat less agitation/fewer inversions works better.
I've had "stains" similar to the ones on your negatives by inverting the tank too many times.

Invert slowly.

Alan9940
25-Feb-2017, 08:18
I use a B&W King tank to develop 4x5 with Pyrocat HD and the recommended agitation method is a twisting action using the lid of the tank. I got very similar uneven development to what you describe and show in the attachments. I eventually worked out an inversion technique and all my issues vanished. I know a lot of photographers swear by 'swirling agitation', but it didn't work out well for me.

Doremus Scudder
25-Feb-2017, 09:49
For some reason, unless you get the agitation just right with 120 film, there is turbulence at the edges resulting in increased edge density (like your examples). If you have an agitation regime that works and consistently delivers even development, go with that! I remember exposing roll after roll of 120 under my enlarger and then processing with different agitation schemes until I hit on one that worked well all the time. Surprisingly, I had to agitate rather vigorously to get even development with 120. When I switched to sheet film and tray processing, I never looked back.

Best,

Doremus

evanmoly
25-Feb-2017, 17:48
For some reason, unless you get the agitation just right with 120 film, there is turbulence at the edges resulting in increased edge density (like your examples). If you have an agitation regime that works and consistently delivers even development, go with that! I remember exposing roll after roll of 120 under my enlarger and then processing with different agitation schemes until I hit on one that worked well all the time. Surprisingly, I had to agitate rather vigorously to get even development with 120. When I switched to sheet film and tray processing, I never looked back.

Best,

Doremus

Thank you for your response. I am going back to inversions for roll film.

However, the swirling technique has worked well for me when loading sheet film into tanks using the 'taco' method since I dont have a space for tray processing (two sheets of 4x5 in a roll film tank with a rubber band around each - bit unorthodox, time consuming, and probably not encouraged by any experts).

I would like to start tray processing my sheet film when I find a space to do it, but I have always wondered - how does one get enough agitation in the tray? It seems like the developer moves so gently across the negative. What have you found to be an effective agitation cycle for tray processing sheet film?

Doremus Scudder
26-Feb-2017, 03:55
Thank you for your response. I am going back to inversions for roll film.

However, the swirling technique has worked well for me when loading sheet film into tanks using the 'taco' method since I dont have a space for tray processing (two sheets of 4x5 in a roll film tank with a rubber band around each - bit unorthodox, time consuming, and probably not encouraged by any experts).

I would like to start tray processing my sheet film when I find a space to do it, but I have always wondered - how does one get enough agitation in the tray? It seems like the developer moves so gently across the negative. What have you found to be an effective agitation cycle for tray processing sheet film?

Evan,

I batch process 4x5 sheets (up to 8, but I like 6 at a time) in deep 5x7 trays and agitate by taking one sheet from the bottom and moving it to the top, submerging it slowly and then repeating. I like to go through the stack once every 30 seconds. When I'm developing just one sheet, I'll lift it from the tray, turn it 180 and resubmerge it in the developer once every 15 seconds. I find tray rocking inadequate.

If you'd like more details, search here or on APUG for some of my (and others') more detailed descriptions of tray processing, or PM me.

Best,

Doremus

koraks
26-Feb-2017, 04:20
Swirling may result in a laminar flow along some parts of the film surface, while obstacles and edges result in turbulent flows in other places. The outcome is unevenness. The only real solution is to make sure the flow is turbulent in all places. An easy way to achieve this is to agitate through inversions - and not too gently at that.
The same issue can occur in Paterson tank with the stick-twisting implement, particularly with 120 film. I find it doesn't cause much problems (at least in my experience) with 135 film, but 120 film is much more finicky due to its large, even surface (no sprocket holes etc.)
Sheet film is an entirely different story as the edges of the separate sheets will induce turbulence in a rotation/twisting agitation scheme, making it a little less prone to uneven development. Mind you: less prone, not immune...
One other instance worth mentioning is agitation in a rotation processor like a Jobo CP*. This can cause issues with partly laminar flows as well, even if the rotation direction is alternated. I find this to be particularly the case at the higher rotation setting of my CPE2 when using roll film. Sheets in a 25xx tank are fine, but 135 film in a 15xx tank is a nightmare with very noticeably higher development along the edges of the film strip.

For me, it helps to visualize what happens in the tank when I run into uneven development issues and then come up with a few hypotheses why it happens. These can be deliberately tested, which usually helps. Similar to Doremus' 120 approach, but a little less random.