Reversal processing in print drums for enlarged negatives

Discussion in 'B&W: Film, Paper, Chemistry' started by John W, Feb 12, 2009.

  1. John W

    John W Member

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    Hi all,

    I'm contemplating(**) making enlarged negatives for contact printing via reversal processing (e.g. using APHS film). After doing my homework on reversal processing, one challenge seems to be that using potassium permanganate as the reversal bleach can result in soft emulsion and resulting emulsion damage, esp. if process temperature isn't well controlled.

    An obvious approach to solving that issue would be to drum process the enlarged negatives, esp. with a water-bath drum processor such as a Dev-Tec model as used for RA-4 printing. The stumbling block using this approach comes in the reexposure phase: how do I manage the reexposure without removing the print film from the drum while it's still prone to damage? Has anyone tried such an approach before? Sadly, my lightsaber is out for CLA so I can't just turn it on through the open drum. :wink:

    This would be rendered moot if I had a reliable chemical reexposure process, but I'm not aware of any published formulas. Likewise, I may eventually work with dichromates for gum printing as well, in which may make sticking to permanganate for the bleach a moot point.

    Does anyone experienced in reversal processing foresee other practical difficulties with a drum processing approach?

    (**) the risk of an idle mind whilst I plan and start construction on my first darkroom... :D
     
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  2. tim_bessell

    tim_bessell Member

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    If you are using APHS film, why use a drum when you can process it under red safelight conditions in a tray, dish, whatever. If you use potassium dichromate the soft emulsion problem is solved. Re-exposure can be done right in the tray as you wash, no lightsaber required. See http://unblinkingeye.com/Articles/NbyR/nbyr.html for starters.
     
  3. tiberiustibz

    tiberiustibz Member

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    Use one of those fogging chemicals like the one in the E-6 Reversal bath.
     
  4. fschifano

    fschifano Member

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  5. Cor

    Cor Member

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    I used Liam Lawless his approach (see also the unblinking eye link), I simply re-exposed the film in the drum: I opened the drum and held it up to a bare light bulb in the ceiling (75 watt), I even put the tank to the ceiling, so the whole bulb "disappeared" (I am tall and my ceiling is low..;-)..). Worked like a charm. I figure that a strong torch for say 30 sec should also work.

    good luck,

    Best,

    Cor

    Ps I use a JOBo I find it more convenient that a try, you need quite some trays, and more fluid, and my darkroom is small..
     
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  6. OP
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    John W

    John W Member

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    My only reason to consider a drum over single-tray processing was for ease of temperature control (using the Dev-tec processor's water bath). And you're right; using potassium dichromate gets me out of that bind. I've perhaps been overly concerned about safe disposal of the dichromate bleach, but on reflection it's not that much more trouble than dealing with spent fix.
     
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    John W

    John W Member

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    That's interesting! I've searched around a bit, but wasn't able to find out much practical discussion of its use. One intriguing aspect of using APHS seems to be that adjustment of Dave Soemarko's LC-1 formula provides some measure of constrast control, potentially useful for fine-tuning the enlarged negative.
     
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    John W

    John W Member

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    Ah, I knew there had to be some info out there. Looking into E-6 process was a useful lead; thanks.

     
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  9. fschifano

    fschifano Member

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    Well John, I haven't tried this stuff yet. I'd be surprised if you couldn't get some sort of contrast control through development with it. I've used APHS to make enlarged interpositives, and from them, enlarged negatives by contact printing the interpositive to another sheet of APHS for the negative. Contrast control is difficult but do-able to an extent. I've tried Dektol 1+9, and that seems to help a bit. HC-110 at 1+63 is a little better because it works more slowly. Perhaps higher dilutions will prove to be better choices. I've read of folks who have used Rodial 1+100 and seem to like that for contrast control. I haven't tried that yet. I don't mind the extra contrast, since I'm thinking of using these enlarged negatives for cyanotypes which could benefit from a higher contrast negative.

    Thanks for pointing out Soemarko's LC-1 developer formula. Seems very easy to mix up. I'll need to give that a try.
     
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    John W

    John W Member

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    I found out about the LC-1 processes from Christopher James' The Book of Alternative Photographic Processes. There's a nice discussion about the LC-1 and LC-1B developers, and the process of contrast adjustment made possible by varying the A and B parts of these formulas.
     
  11. tim_bessell

    tim_bessell Member

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    John,

    One thing you will find and this is using the Liam Lawless approach, is that your initial image and flash exposure is the control for contrast. As the article @ unblinkingeye.com says, develop to completion. I know it is a hard concept to grasp. Using LC-1 will not help in this particular process. The final re exposure is also done to completion, since the bleach step has removed all unneeded developed silver.
     
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    John W

    John W Member

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    Ah! Thanks for pointing this out! I'd quickly skimmed Ed Buffaloe's article on unblinkingeye yesterday, but I hadn't had time to let the implications of the flash exposure sink in.

    For other folks just sorting this out, the insight is as follows. After the initial exposure, the highlights will have some base exposure (call it one unit) while the shadows will have several stops more exposure (let's say 33 total units). Thus we have about a five-stop exposure range between shadows and highlights.

    Let's say the flash step applies a constant 15 units of additional exposure to both shadows and highlights. This now gives us 16 units of exposure in the highlights and 48 units of exposure in the shadows. This reduces the overall contrast greatly, to about 1.6 stops. (log_2(48/16))
     
  13. cchisena

    cchisena Member

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    Reversal processing in drums

    I have been using drums,BPFB18 film, and T Max Reversal Chemistry for dupes for several months.The chemistry requires no light reversal step and seems to reverse any film I've tried.However, even with a very good densitometer,there is not a lot of control with that chemistry.The Photo Warehouse film is X-ray duplicating film I believe and is also not easy to work with. I am coming around to using APHS and using 2 steps(interpositive) or BPFB18 film and 2 steps.The Bergger film is very expensive,but also excellent.I am beginning to think that seeing the interpositive and working on it may be the better way to high quality results.I hope someone can answer what is the best way.All I read is that even digital may not be as good,but very close.I'd like to stay analog, but I'd like any help or ideas to make it better.