Jobo tanks, Constant Agitation (Uniroller) and Fluid Quantities

[JWMster]

Fairly simple question I think I know the answer to, but would like confirmation before processing:

With Jobo tanks, the fluid quantity minimums are for the number of FILMS, not the number of reels, right? This is my default since chemistry minimums tend to be driven by square inches of film in the tank. I've a tank that will hold 3 reels of 120, and though each reel can do 2 films (to make 6 films), I'm not ready for that an running 3 films on 3 reels - because it is EASIER. After I've done this a few times, I might decide to try 2 films per reel, but not at the start.

Beyond that, the minimum levels are suggested to be minimums. I wonder when this number is 550ML how many are actually using quantities north of that? Say 600ML or 750ML? Just curious.

THanks!

 

[Willyekerslike]

The info on my Jobo 1520 tank states Rotation: 240ml, Inversion 485ml. It then lists the number of films that the tank will take. 110 films 8, 126 films 4, 135 films 2, 120 films 2 and 220 films 1. For rotation I always use 240mls irespective of the number of films in the tank. I do not use Jobo tanks for inversion. Hope this helps

Regards...W.

 

[CCLA]

For rotation purposes you cannot go below the minimum quantity or the center of the reel might not get enough chemistry.
I also never used inversion on Jobo tanks.

claudio

 

[grahamp]

For inversion you need at least enough solution to cover the reel(s) holding film. You may need more - it depends on the developer capacity, not the tank size. For rotation, there is a minimum tank volume, irrespective of reels used. There is also a maximum based on the size of the tank and the capability of the machine. So highly dilute developers usually limit the number of films in a load in order to have enough active ingredients in the solution without exceeding the capacity of the machine. With inversion, the volume maximum is the capacity of the tank.

Developers have a capacity (1 35mm approximates 1 x 120, 4 x 4x5, 1 x 8x10) for a given volume of solution. You have to allow at least enough volume to fully immerse the film using inversion or rotation, and also allow enough volume to provide the active ingredients needed for the area of film - whichever is the greater. Most film recipes, if they do not say otherwise, should develop a 35mm film in the minimum volume required for immersion using inversion agitation.