How much developer

Discussion in 'Darkroom Equipment' started by Erik Hartmann, Jul 14, 2008.

  1. Erik Hartmann

    Erik Hartmann Member

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    I have got a Jobodrum 4531, witch take four 13x18 negatives.....
    How much developer (fixer) ect. do I have to use.... And developing time when I use the Durst Camot rolling machine....
    Hope to get an answer here......
     
  2. 2F/2F

    2F/2F Member

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    The tank itself should list minimum chemical volume on the side. If you go to Jobo's Website, you can find the max. chemical volumes. (For my 3010 tank, it is 210mL minimum, 350mL maximum, but I did not know about the max. until I did some research.)

    As for amount of developer stock needed, it will depend on your developer. With four 13x18cm negs, you need enough developer stock to do two rolls of 135/120, regardless of dilution.

    BTW, you have the same name (different spelling) as the world's top flying ace of all time (but you probably already know that).
     
  3. Erik Hartmann

    Erik Hartmann Member

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    2F/2F

    "BTW, you have the same name (different spelling) as the world's top flying ace of all time (but you probably already know that)."

    NO.... I do not know anything about that..... please tell !!!
    And I cant find anything about that old drum on Jobo's web-site (sorry)
     
  4. rwyoung

    rwyoung Member

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    The MINIMUM amount of developer is primarily a function of film surface area and developer type. For example, Rodinal (R09) the rule of thumb is 5ml of developer per 80 square inches of film. Some will say 6ml, others 10ml. Fine, Rodinal is cheap so lets just say 10ml so we don't have to worry about it being exhausted.

    80sq inches = 516sq cm

    13x18cm=234sq cm

    So for all intents and purposes, being generous with the rounding and assuming 10ml / 80sq-in, with Rodinal it would be 5ml per sheet (516 / 234 = 2.2, which means it takes 2.2 sheets of 13x18 to equal 80 square inches of film).

    Now you can use this to work backwards from the dilution ratios to what your tank can really hold. Same sort of calculation can be done for other developers but you need to first find out the recommended minimum stock solution for some given surface area of film and work backwards to your film size and sheet count.

    Next you need to decide how much fluid the tank will hold and still spin on your rotary base without overloading the motor. With the 2905 (I think that is the tank number) it will physically hold something like a liter of fluid but the rotary capacity is 240ml. So about 1/4 max capacity. But in the case of the big 16x20 print drum I have, it says something like 120ml rotary capacity but filled full it is LOTS and LOTS of fluid.

    Personally, I run them both at 240ml (and use PyrocatHD or Rodinal). I do feel that the motor housing is warmer when I run the 16x20 drum with 240ml so perhaps I'm going to shorten my Jobo's life span.

    You could try a simple experiment and find your comfort level. Spin an empty tank for 10 minutes and feel the motor housing (or tape a thermometer to it). Record the temperature rise. Let the housing cool back to room temperature again. Fill your tank 1/4 with fluid and run again. If the temperature rise is similar after 10 minutes then I would feel comfortable with that volume of developer / fixer in the tank.

    By the way, if you wanted to, you could fix with the tank on the table and just fill it with fixer until full. Then agitate by hand. Same goes for stop bath and HCA if you decide to use them.
     
  5. RobC

    RobC Member

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  6. RobC

    RobC Member

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    I rekon 300ml will do it for you as the film is held at the edge of that tank so 300ml will cover the film and be enough to develop that area (140insĀ²).
     
  7. Erik Hartmann

    Erik Hartmann Member

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    Thanks RW and Rob.... Now I am going to develop safely......
     
  8. RobC

    RobC Member

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    p.s. I based the 300ml figure on the 2521 tank which requires 270ml for 6 sheets of 4x5 (120insĀ²). But those 6 sheets protude further into centre of the 2521 tank than yours will so 300ml should easily do it providing its the right strength. I'm assuming you are using the plastic sheet which fits around the inside edge of the tank.
     
  9. Erik Hartmann

    Erik Hartmann Member

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    ROB.... there are some plastic 'things' that keeps the films on there right place.... think (hope) that is OK.... going to try it to morrow........
     
  10. RobC

    RobC Member

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    If you just acquired this tank I would give everything inside it a very thorough clean. If it has been used for colour prints chemical contamination is a very real risk.

    If you have been doing hand inversion with intermittent agitation, then as a starting point reduce development time by 15% when using constant agitation on a roller base. You will have to experiment with time as it could be as much as 25% less. It really depends on your previous procedures so I can't be precise.