Kodak Flexicolor - experimental replenishment - Jobo centric.

AgX · Aug 25, 2020

Donald Qualls said:
As I recall from discussions when PE was involved, if you follow Jobo's instructions on how much chemistry to use in the rotary systems, you'll be exhausting your chemistry more in a single use than you ever would in an inversion system, and then pouring (part of) that back into the stock bottle.

In a inversion process you have about 1/2 of the exhaustion, but then also you put twice the amount back into the stock solution compared to rotation processing. In the end, that is in the stock solution bottle, the situation will be exhaustion-wise the same for both inversion and rotation. So, on this your argument is invalid.

What may matter though is whether during the processing the rather small volume per film area is depleted to a degree affecting good processing.

Jobo processors though have been used in commercial photography over here for decades and I never heard of depletion issues.

Furthermore, by putting the cap on the tank (driven by its bottom end) one can easily highten the used volume.
And one then can do sensitometric tests under same processing dynamics, on whether there is a difference in outcome depending on used volume.

Mr Bill · Aug 25, 2020

Tom Kershaw said:
To update this thread I'd like to report that last week my replenished Flexicolor developer ceased to function correctly...

Hi, thanks for the update... this may save some trouble for other Jobo users.

As I said in post #14 the color developers rely on having a relatively small, and consistent, concentration of preservatives. So I'd guess that this has a lot to do with what you found, a lot of the preservatives are oxidized in the Jobo tank.

As a note, I had roughed out some calculations as to how much of the developing agent and preservatives could be oxidized by the oxygen contained in a Jobo tank. (I though I had posted this, but I guess not.) From my recollection I think that a single Jobo run could potentially kill off about half the developing agent and preservatives, depending on the tank size, etc. This seems like it would have a tremendous impact on the quality of the processing, which seems likely to NOT be occurring, just based on random forum chatter. So my presumption is that the reaction takes a bit of time to occur, and that the time factor predominates over the total oxygen in these cases. But I could be wrong. It's too bad there's not a cheap and easy way to fill the Jobo tank with an "inert" gas.

Lachlan Young · Aug 25, 2020

Mr Bill said:
It's too bad there's not a cheap and easy way to fill the Jobo tank with an "inert" gas.

And if you're doing so, you might as well adopt nitrogen gas burst agitation...

I've found that negs developed in single shot C-41 in a Jobo are generally more consistently well behaved than most replenished systems - even well run dip/dunk systems. If you use a decent amount of Portra 800, it pretty rapidly becomes apparent who is and isn't replenishing at the right rates...

AgX · Aug 25, 2020

Mr Bill said:
As a note, I had roughed out some calculations as to how much of the developing agent and preservatives could be oxidized by the oxygen contained in a Jobo tank. From my recollection I think that a single Jobo run could potentially kill off about half the developing agent and preservatives, depending on the tank size, etc.

On one hand the surface of the bath in a rotating tank is quite large. On the other hand the bath is only facing these circumstances for a few minutes, before it goes back (in a replenishing process) into its bottle, maybe even under inert gas.

The same bath though may be in a mini-lab processor for days or even weeks under replenishing.

Tom Kershaw · Aug 25, 2020

Lachlan Young said:
I've found that negs developed in single shot C-41 in a Jobo are generally more consistently well behaved than most replenished systems - even well run dip/dunk systems. If you use a decent amount of Portra 800, it pretty rapidly becomes apparent who is and isn't replenishing at the right rates...

Good point about the Portra 800. As I do my own processing I don't have any recent experience of sending film away. I'm not sure what level of quality to expect back...

Lachlan Young · Aug 25, 2020

Tom Kershaw said:
Good point about the Portra 800. As I do my own processing I don't have any recent experience of sending film away. I'm not sure what level of quality to expect back...

It's more what I've seen from what people got back from other places - it's supposed to look much the same as the other Portra bases...

Tom Kershaw · Aug 25, 2020

Lachlan Young said:
It's more what I've seen from what people got back from other places - it's supposed to look much the same as the other Portra bases...

Ah ok, I see what you mean about replenishment rates then.

Donald Qualls · Aug 25, 2020

Mr Bill said:
It's too bad there's not a cheap and easy way to fill the Jobo tank with an "inert" gas.

I don't know the Jobo system well, but if it's all electronic switching (as opposed to, say, microswitches and relays) and an induction motor (vs. an AC/DC universal brush motor) to drive the rotation, butane for lighter fuel would be safe. It's fairly cheap and fully inert relative to photographic developers. Flammability is the only issue -- in a chemical storage bottle it's fine, once closed with air excluded there's no oxygen for it to combust with, but in a Jobo tank, open to the air (and actively mixed with that air due to agitation) a spark could be bad. Argon sold for air exclusion is, as I recall, about three times the cost per similar size container, and butane stores as a liquid that expands tens of times on release, while argon is just a compressed gas. In between is "canned air" which isn't (as) flammable, is liquid in the can, but costs more than lighter butane.

mshchem · Aug 25, 2020

First thanks for the update.
I received a 10 sheet box of 8x10 Portra 160 today. I got it on sale, free shipping from Adorama in NYC. Only 14 dollars a sheet. I don't have color capacity with my 8x10 enlarger so I got the idea, and I think it will work great to make contact prints. I have 4x5 color enlargers so light source is easy.

I'm going to be processing in a Jobo 3005 on CPP3. There's part of me that wants to use hangers in 1 gallon tanks. I have a temperature controlled 8x10 setup for 8 1 gallon stainless tanks.

There's still part of me that thinks Jobo is radical, even though I've used one for several years now. There's just something so elegant about regular old school ways of doing things.
Best Mike

Lachlan Young · Aug 25, 2020

mshchem said:
There's part of me that wants to use hangers in 1 gallon tanks. I have a temperature controlled 8x10 setup for 8 1 gallon stainless tanks.

You might want to read up on Kodak's documents about sink-line processing C-41 - you ideally need both manual and gas agitation as I recall.

mshchem · Aug 25, 2020

Lachlan Young said:
You might want to read up on Kodak's documents about sink-line processing C-41 - you ideally need both manual and gas agitation as I recall.

Oh I've done it without the gas. No problems at all. Kodak has more published on deep tank use than for Jobo. I'm sure I will use the Jobo, so easy.

MattKing · Aug 25, 2020

Donald Qualls said:
Flammability is the only issue

Now here is a great entry for the "famous last words" contest!
Although right now the Hindenburg still has a lead.

Kodak Flexicolor - experimental replenishment - Jobo centric.

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