These days Anne Larsen often does that part. The cool part is that they do two sheets at a time like this. The two sheets are back to back (obviously) and flipped together for the full 2 minutes in Dektol.Originally Posted by Ben Calwell
These days Anne Larsen often does that part. The cool part is that they do two sheets at a time like this. The two sheets are back to back (obviously) and flipped together for the full 2 minutes in Dektol.
It is possible lack of adequate flow behind the paper might cause problems such as stains, but not overall emulsion fog unless, for example, one is not using an acid stop bath, and is using an alkaline fixer, or perhaps if temperatures are ridiculously high or something.
In any case, with general purpose chemicals, fog should not have anything to do with agitation/aerial oxidation.
If the paper is floppy around to a certain extent, due to being softened, what constitutes its front versus the back is somewhat unpredictable. Who knows in this case. It will have to become an experiment in resolving the variables one at a time. 16X20 is a rather big FB print size for successful drum use. What I've thought of hypothetically doing is using thin fiberglass or carbon fiber spring rods in the drum diameter to hold paper in place at both ends. Never got around to that experiment because I didn't need to. Removable moisture and chemical-resistant lacquer-style masking tape could also be hypothetically used.
Fog from "flopping around" when developing fiber-based paper in a Jobo drum isn't an issue. That process was well documented. Rather, the challenge is paper being "plastered up against" drum ribs and deforming. Scott Jones worked it all out two decades ago. Here are forum threads in which he walked everyone through the necessary steps:
I cannot offer Marco any advice on the fog increase, but don't recall Scott ever reporting that he experienced it.
The answers so far -- thank you very much to all of you for the help, by the way -- seem to belong to two categories: the former is "if that happens can be caused by this or that", the latter is "it should not happen / there is something wrong". The good observation that Sal has made is that Scott Jones would have noticed it.
I am working on profiling various positive papers and reversed negative papers for in-camera photography, and this increase in fog when I switch from trays to the Jobo happens only with fiber-based papers. That's why I asked if in the standard negative-positive process of developing fiber-based papers with the Jobo (so, no positive paper or reversal development stuff that complicates the story) a notable increase in fog is known to be a problem. From the above I would say that the answer is "no." There may be problems related to the ridges in the drums, I get that, but nobody has ever mentioned an increased fog.
As soon as I have an afternoon free I will contact print a couple of 4x5 Ilford FB sheets with a Stouffer TP4x5, develop one in trays, the other with the Jobo and see what happens when I remove all this positive or negative-reversal development business. And report here what I get.
To answer your question: when I develop the 4x5 FB sheets in trays I do the hypo bath in tray and the wash in tray. When I develop the 4x5 sheets in the Jobo the hypo bath is still done in the drum, the wash in tray. The subject is a Stouffer R2120 step-wedge that I measure with a Heiland TRD2 densitometer.
[QUOTE=Marco Annaratone;1596665 . . . is it maybe common knowledge that the development of fiber-based paper in the Jobo increases fog compared to tray development? . . . [/QUOTE]
Might the same be true of film when developed in a Jobo, versus tray development?
Several people in photrio.com developed FB paper in a Jobo, nobody mentions an issue with fog. Except one OP but he says that when he bought new paper the problem did not occur any more. Go figure ...
Marco, you haven’t mentioned the chemicals/process. It could (possibly) help diagnose the problem.
-Developer
-Stop bath? Acid or water? How long?
-Fixer type? Acid or alkaline?
I did that on purpose. We are talking about four different papers, three different developers, plus a proprietary reversal process. That's why I restricted my initial question to one specific issue, i.e., whether it is a known fact that using the Jobo increases the fog in a more conventional fiber-based paper development process. I did not want to go into the rabbit hole of splicing and dicing processes that may have nothing to do with the problem. With some papers I use a stop bath, with others I do not. With some I use Ilford MG as developer, with others a proprietary developer. It suffices to say though that the development chain is _identical_ (concentration, times, temperatures, etc etc etc etc) in trays and Jobo. With the resin-coated paper I measure no differences between trays and Jobo, with fiber-based paper my base+fog jumps 0.10-0.14 when I move from trays to the Jobo. Every time, consistently.
Before looking into the specifics of my own processes, I wanted to make sure that the fogging with fiber-based paper was not something that everybody but me :-) knew about it. (I have been using the Jobo for almost ten years, but only with with RC paper.)
No one has mentioned developer oxidation and subsequent emulsion staining yet. I've had some issues with this with a couple of different developers (especially when the developer has had a few prints run through it).
Since you don't want to divulge which developers you are using, I can't speak directly to them. However, if oxidation and staining is the problem, anything that helps reduce developer oxidation should help. That means slower agitation (or even rolling the drum by hand), maybe adding a bit more sulfite to the developer and using the freshest developer you can.
If you can eliminate the fog/staining by slowing agitation and using fresh developer, then this is almost certainly your problem.
Best,
Doremus
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