Two for One?

Discussion in 'B&W: Film, Paper, Chemistry' started by sircarl, Jun 11, 2008.

  1. sircarl

    sircarl Member

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    With my Jobo 1520 tank, it is possible to process two rolls of 35mm film or 120 film at the same time, in 500ml of developer. I've tried this occasionally, but not always with good results. Will 500ml of a developer always be sufficient to handle two rolls? (Some developer instructions say don't re-use after processing one roll, which seems to imply it can't handle two.) Would I need to use a different -- i.e., increased -- agitation with two reels in the tank (for 35mm film) or two rolls of film on one reel (with 120 film)? I'm using mainly DDX and Perceptol, by the way. Would be grateful for any suggestions.
     
  2. MikeSeb

    MikeSeb Member

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    For every developer, there's a minimum volume of stock solution (regardless of dilution) required to develop an 8x10 sheet equivalent (ca. = 135-36 or 120 roll). For Xtol, it's about 100mL; for D-76, I think it's 200 or 250; for HC-110, it's about 6mL of syrup concentrate. Not sure what it is for Perceptol or DD-X; find out what that number is and you're golden. But since developer is cheap and your time and effort aren't, don't skimp.

    So used straight, for instance, I need about 200mL of Xtol to process two 120 rolls. Presumably, it takes 100mL worth of developer "activity" to process the 80 or so square inches of film surface area in a roll/sheet. Diluted 1+1, I still need 200mL of stock, but I've diluted it, so I need 400mL of the working solution. Make sense?

    Now, the Jobo also has a minimum solution volume--required to actually immerse and cover the film in the tank--which should be found engraved somewhere on either the tanks or the processors. You'll need to use whichever volume of solution is greater--the Jobo's required minimum WORKING solution, or the developer's required minimum of STOCK solution, however diluted. For instance, my Jobo requires about 175mL for a single roll, which means I'd need 175mL of solution to cover the film in the tank. Straight, that's almost double the film's minimum Xtol requirement; diluted 1+1, I'd need 200mL of working solution to give the film its 100mL and still give the Jobo its 175.

    In your case, your Jobo seems to require 500mL to do two rolls. Using 500 mL of Xtol straight, you're well above the 100mL/roll developer minimum; even diluted 1+1, you have a comfortable margin of 250mL stock for two rolls. For you, using Xtol at 1+1 would be the economical choice, rather than straight, all else being equal. If you decided to use Xtol 1+2, you'd need 600mL of working solution to make the film happy, which is more than the 500mL needed to satisfy the Jobo. At 1+3, the film wants 800mL of working solution, and the Jobo is fine with it as long as it's not overflowing. I find that I am frequently up against the tank's maximum solution capacity when using very dilute developers--the tank is full and I still don't have the required minimum amount of stock to develop the film--this limits me to 1+1 or 1+2 in most cases.

    Clear as mud? Much harder to read than to conceptualize, and do. So the key is to find out how much Perceptol or DD-X concentrate or stock solution is required per roll, and then you'll know the rest.
     
  3. sircarl

    sircarl Member

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    Mike,

    Thanks for that. I just checked Ilford's fact sheets for these developers. They don't tell you how much concentrate or stock solution is required per roll. They just say how many rolls a liter of developer solution will process. It appears that at standard strength -- which is what I use -- either developer should be enough to process two films in a 500ml tank. But then Ilford goes on to say that "for highest image quality" they "should be used as one-shot developers," which may be read as implying processing more than one roll in 500ml might be less than ideal. Maybe I should just experiment to find out. The fact sheets say nothing about using an altered agitation routine if you load two films into a 500ml tank.
     
  4. mono

    mono Subscriber

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    For Perceptol it is 250 ml per film.
     
  5. Bob F.

    Bob F. Member

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    Not sure if I understand your dilemma correctly but, developing two rolls at the same time is much the same as developing one roll in half as much chemistry as far as I know. Certainly I have never worried about developing multiple rolls at the same time as long as there is sufficient stock chemical for the area of film.

    What most manufacturers recommend against is using the same developer twice - i.e. don't develop one film and then re-use it for another film afterwards. I believe this is mainly because of development by-products (halides?) and dyes etc which will build up in the developer if it is re-used. This does not happen when you process twice as many films in twice as much chemical at the same time. There are a number of chemists here who can correct me if I am wrong here...

    I do not alter agitation with the number of rolls but I can see if you had one of those big Paterson tanks that hold up to 8 reels you might want to!

    Have fun, Bob.
     
  6. sircarl

    sircarl Member

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    Thanks to everyone for the helpful comments. I developed 4 rolls of 35mm Delta 100 in DDX yesterday -- two for the normal time (for the speed I rated it at), two for a somewhat longer time. The second batch came out slightly better, which is what I expected. I have a feeling two rolls in a Jobo tank does inhibit the normal flow of developer, making a longer time (or greater agitation) necessary. Having said all this, I don't plan on doing two rolls at a time too often. It just makes me jumpy!
     
  7. bdial

    bdial Subscriber

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    You state that you are using a Jobo tank, but are you using it on a Jobo base with rotation, or upright and static (and agitating by inversion)?
    If you're using it with inversion, you need to fill the tank completely. I'd have to look, but the tank probably needs more than 500 ml for two rolls if you aren't using rotation.
    Increased agitation won't compensate for inadequate developer volume.
     
  8. pentaxuser

    pentaxuser Subscriber

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    The 1520 needs 240ml for two films by rotation and 485ml for inversion so 500ml which takes the liquid to the very top is more than enough. There's even an argument that you should stick to 485 which is just over the reels but allows enought space for agitation. If you fill it completely then less agitation is possible, possibly having an effect on development

    pentaxuser
     
  9. pentaxuser

    pentaxuser Subscriber

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    Folker. Where does this figure come from and do you mean a total of 250ml of liquid at any dilution level such as 1+1 and 1+3 or 250ml of Perceptol at stock solution?

    pentaxuser