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......
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.
