Mistery flowmarks on C41 negatives from dip and dunk

[John Salim]

Hi John, thank you for the message.

Cycle is 3s ON, 7s OFF. There is also a 1s pre-agitation setting that happens just before the rack lands.
The machine does not burst while transporting but I guess the pre-agitation happens at the very last moment of the lift movement if that's what you mean.

E

Hi E,
Well that all sounds fine to me, though 3" seems a little long and 7" sounds short ( but not critical )
The developer solution should rise about an inch during burst.

John S

 

[owk.edo]

Hi E,
Well that all sounds fine to me, though 3" seems a little long and 7" sounds short ( but not critical )
The developer solution should rise about an inch during burst.

John S

Hi John
interesting, they were set that way by the engineer and slightly adjusted by me once the densitometry line was up.
The solution does rise about an inch with the burst but I did notice quite a lot of bubbles/foam with somewhat intensive throughput of rolls.
Do you think excessive foaming and bubbles hanging onto the film in between lifts could be the cause of this?

thank you for your input

E

 

[koraks]

Do you think excessive foaming and bubbles hanging onto the film in between lifts could be the cause of this?

How long does it take between the film exiting the development bath and dropping into the stop bath?

 

[owk.edo]

How long does it take between the film exiting the development bath and dropping into the stop bath?

The lift cycle takes 27s to complete, including 8s of drip time. There is no stop bath, the film goes from the developer straight into the bleach

 

[owk.edo]

The lift cycle takes 27s to complete, including 8s of drip time. There is no stop bath, the film goes from the developer straight into the bleach

I'd like to point out that this setting has been unchanged since the machine was installed 4 years ago and the issue at hand has only started happening recently

 

[koraks]

Sorry, of course; no stop bath.
OK, 27 seconds is a long time and if you have foam dripping off of the film that might indeed be a problem.

Can you actually see foam sliding down the film at a slow pace?

Has the developer bath always foamed like this?

 

[owk.edo]

Has the developer bath always foamed like this?

Yes, pretty much. Maybe in different amounts over the years but not having any issues with negatives or densitometry so far made me feel confident with the way things were going or at least I haven't really monitored these aspects closely. I understand now this might have been an oversight.

The question of how this only started happening recently still bothers me but at least I have one more thing to look at before I dump the chemistry.

 

[koraks]

Yes, I agree, it's odd that there's a problem now where there wasn't one before and you've not seen a clear change.

Btw, as to the foaming: to promote even wetting, color developers tend to contain wetting agents/surfactants and these can contribute to bubbles and some foaming. How this interacts in a d&d system I really don't know, I can only attest to the fact that a little foaming is normal. But foam sticking to the film surface isn't; the developer should really sheet cleanly off of the film as the film is pulled out of the bath. Hence my question if you see foam clinging to it (on a test run in daylight).

 

[owk.edo]

Thank you for the insight, it makes sense!
I'll be running some tests in daylight tomorrow and hopefully have good news.

 

[Lachlan Young]

27 seconds is a long time and if you have foam dripping off of the film that might indeed be a problem

As long as it's accounted for within the development time etc, it should not be an issue - e.g. even something much smaller like a Jobo Autolab takes about 15s to tip out C-41 dev and runs the pump for the bleach for about 12s.

While I do suspect that the lifts/ bursts might have to do with the current issue - for example, there are known issues with the length of time for submergence relative to time taken for development to start on 8x10 film when 2 sheets are above each other on the rack, it is also known that under some circumstances, certain surfactants can act as development accelerators (due to enhancing emulsion swell, for example) and even very slight carryover of a few drips in the clips from the final rinse + a small coating package change (e.g. when Portra went from CTA to PET in rollfilm) might be all it takes to cause problems within the first 15-30s of development, in line with the vertical direction of the hanger travel.

 

[John Salim]

I don't believe this is an agitation or tank transfer problem E.

However if you're processing up to 120 rolls a week for a 60 Ltr dev tank, you might not be processing enough rolls to turn the tank over sufficiently.
I'm not entirely sure with C-41, but estimate you should be processing around 180+ rolls a week.

Does this problem happen with a fresh tank or only after a few weeks ?

John S

 

[Lachlan Young]

I don't believe this is an agitation or tank transfer problem E

Generally I'd agree, especially as the relative level of dilution is vast, but I have encountered cases where people managed to get small amounts of wetting agent residue on to the film before it went in the developer.

However if you're processing up to 120 rolls a week for a 60 Ltr dev tank, you might not be processing enough rolls to turn the tank over sufficiently.
I'm not entirely sure with C-41, but estimate you should be processing around 180+ rolls a week.

If it's the chemistry I think it is, it's supposed to be run at 60ml per 135/36 or 120, rather than the high replenishment rate of something like Fuji 60 AC (90ml per 135/36) that's designed for very low usage.

The instructions are also pretty clear about not leaving working strength replenisher standing for more than a week.

 

[koraks]

you might not be processing enough rolls to turn the tank over sufficiently.

Whether or not that's the case, that wouldn't explain this failure mode. It might be an additional problem, but I doubt it is because the densitometry apparently tracks OK.

 

[John Salim]

Whether or not that's the case, that wouldn't explain this failure mode. It might be an additional problem, but I doubt it is because the densitometry apparently tracks OK.

I know densitometry records fine, but I was thinking possibly developer by-products building up ???
I'd like to know if this happens with a fresh tank at start up.

John S

 

[koraks]

I was thinking possibly developer by-products building up ???

Sure, but those would affect densitometry, and they would not cause uneven development. They will affect curve shape, tracking between curves and gamma.