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Thread: Higher fog in rotary development of fiber-based paper?

  1. #1

    Higher fog in rotary development of fiber-based paper?

    I am getting strange results but before searching for the culprit well hidden in my development chain I must ask: is it maybe common knowledge that the development of fiber-based paper in the Jobo increases fog compared to tray development? I am getting differences in the density of 0.1 in base+fog between tray development and rotary/Jobo development. And this higher fog is quite visible. Please assume that there is no obvious reason (light leaks etc), I went through those already myself. Assume same batch of paper, same development temperature, same concentration, same developer from same bottle, same development time. I have six pairs of sheets (six in trays, six with Jobo) and all of them show this, so it is not a fluke, there is something structural going on. Important data point: the tests I have done with resin-coated paper show no appreciable difference between tray and rotary/Jobo development re: base+fog.

    Dmax is instead comparable.

    Thanks!

  2. #2
    Drew Wiley
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    Re: Higher fog in rotary development of fiber-based paper?

    Jobo is a high RPM system, and you're going to get a lot more agitation and oxidation than tray development. Some people develop film in rotary drums, or RC color papers, but not fiber-based paper. Why do you need to do it in a drum? FB paper sizes get soggy and collapses to an extent in a drum, exposing it to intermittent air and uneven development. Not recommended.

  3. #3

    Re: Higher fog in rotary development of fiber-based paper?

    Quote Originally Posted by Drew Wiley View Post
    Why do you need to do it in a drum?
    When I print 16x20 my darkroom is too small to use trays large enough for this size. Hence ... the Jobo

    (And unfortunately I develop 16x20 prints 70% of the time.)

    Could slowing down the rotation -- say to 'F' instead of 'P' -- help?

  4. #4
    Drew Wiley
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    Re: Higher fog in rotary development of fiber-based paper?

    Jobo just doesn't go slow enough in my opinion. But try the slowest speed. And it might be worthwhile to try displacing any air inside the drum with an inert gas like argon, which is sometimes done to prevent excess oxidation with certain film developers too. You might also try a removable tape on corners and edges of the paper inside the drum, when the drum is still dry.

  5. #5

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    Re: Higher fog in rotary development of fiber-based paper?

    Something doesn't sound right about this. You should not be getting development fog on paper even with relatively violent agitation - unless there is something strange about the developer.

    For example, John Sexton develops his prints by quickly and continuously yanking the prints out of the tray and slapping them back down (thwap!...thwap!...thwap!...). A Jobo drum rotating at virtually any of its speed settings should not cause paper fog.

    Agitation, in and of itself, should not influence fog. Nor should aerial oxidation have any impact on fog under normal circumstances with general purpose print developers.

  6. #6
    Drew Wiley
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    Re: Higher fog in rotary development of fiber-based paper?

    Spoken from experience, Michael? I doubt it. There are certain reasons why almost nobody develops FB papers in drums. There was an early Kodak drum system which retained prints using an overlying screen. It was allegedly a finicky system. RC prints don't soak in the solution deeply like FB prints, so retain their shape in a rotating drum. A separate factor is that some drum don't allow for consistent solution flow or drainage behind the print. So chemical residue can get trapped back there, and then potentially come out at the wrong time. That has to be tested for too. We don't know the specific developer or fixer in question either, or if exhaustion of one or the other is involved.

  7. #7
    jp's Avatar
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    Re: Higher fog in rotary development of fiber-based paper?

    I am wondering if things don't get clean in the drum as chemicals change... The FB paper would absorb more and drain slower. Perhaps try a water rinse after developer and stop bath. I have not used drums for prints except for color back in the 1990's and it was too much work then.

    Can you build some shelves to stack trays and use trays? It seems trays stacked would not take up any more space than a jobo processor.

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    Re: Higher fog in rotary development of fiber-based paper?

    Quote Originally Posted by Michael R View Post
    Something doesn't sound right about this. You should not be getting development fog on paper even with relatively violent agitation - unless there is something strange about the developer.

    For example, John Sexton develops his prints by quickly and continuously yanking the prints out of the tray and slapping them back down (thwap!...thwap!...thwap!...). A Jobo drum rotating at virtually any of its speed settings should not cause paper fog.

    Agitation, in and of itself, should not influence fog. Nor should aerial oxidation have any impact on fog under normal circumstances with general purpose print developers.
    I hope John Sexton wears old clothes or an apron when he's splashing about in the darkroom!

  9. #9
    Drew Wiley
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    Re: Higher fog in rotary development of fiber-based paper?

    I recommend amidol for those sloshing activities. That way you can prove what you were doing, regardless of how the prints come out. Tie-dyed head to toe, and of course, black fingernails too, just like a heavy metal rocker.

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    Re: Higher fog in rotary development of fiber-based paper?

    The fog applies equally to print borders and highlights? Are you doing washing in the tank, or in a washer? This information is not in the original post.

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