Jobo processor question regarding to a DIY build

Hi all

I recently started looking at the jobo processors as I want to rotary process my film and be able to develop C-41 at home.

Now I almost figured out everything about the machine to make my own, using jobo tanks.
It seems that the tank is lying in the water when it's rotating. Is it to keep the water moving or keep the tank on temperature? Because it's only just a bit in the water... and it seems unlikely that it could keep the tank on temperature like that.

Many thanks in advance

Most Jobo processors use the water bath to keep the chemicals in the rotating tank at a constant temperature. At least one model used heated air. There is about a one degree C difference between the tank and the waterbath. This is taken into account in calibrating the waterbath temperature readout on some models.

Don't forget that the whole of the tank revolves in the water bath, albeit a bit at a time so it experiences the equivalent of being submersed in the water bath. This is enough to keep the developer, bleach, fix etc at a constant temperature.

There should be a white line in the water bath to which you should ensure the water reaches. If the chemicals have been immersed in the water bath for long enough to reach the correct temperature before being poured into the tank and the film has been brought to the same temperature by a pre-soak then the film is developed as it should be, at the correct temperature.

So in short the tank is meant to revolve with the correct portion of its bottom part in a constant temperature water bath which maintains each chemical at the correct temperature.

I hope this covers your question

pentaxuser

It covered my question. Thanks !

I always fill it as full as possible to get the maximum amount of waterbath touching the tank, to keep the temps as constant as possible.
That amount is, of course, limited by the fact that the tank floats with no chems in it, if it does I drain the bath just enough for it to sit on the rollers and not pop off the cog.

Don't forget the pre-wet which is intended to temper everything, tank and reels along with the film. This provides a big boost in overall stability of the temp.

PE

Photo Engineer said:

Don't forget the pre-wet which is intended to temper everything, tank and reels along with the film. This provides a big boost in overall stability of the temp.

PE

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Don't forget to do the pre-pre-wet running of the tank to bring the tank up to temperature. This will help to eliminate any temperature shock when you commence your pre-wet.

LJH said:

Don't forget to do the pre-pre-wet running of the tank to bring the tank up to temperature. This will help to eliminate any temperature shock when you commence your pre-wet.

Click to expand...

HUH? Whats with all the pre's?

Pre-wet is filling the tank with water up-to-temp and wetting the film, it gets the film up to temp and swells the emulsion or something on the film. I don't do it for B+W nor E6, can't remember what I did for C41 besides follow the instructions (only done C41 once).
The other pre-pre-wet is just running the jobo for a few minutes in the water bath with no chems, the warm the tank. You can't overdo this, last E6 I did I just left it running for half an hour while I did other stuff to make sure everything is correct temp.

fotch said:

HUH? Whats with all the pre's?

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To heat the drum to temperature prior to inserting the developer use a five minute run with the tank filled with film but no fluid.

ic-racer said:

To heat the drum to temperature prior to inserting the developer use a five minute run with the tank filled with film but no fluid.

Click to expand...

+1

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ic-racer said:

To heat the drum to temperature prior to inserting the developer use a five minute run with the tank filled with film but no fluid.

Click to expand...

This also recommeded by Jobo for Delta films and Xtol. NO PRE-WASH. Pre-temper.