Help Diagnosing 2 Different Problems

[RJ-]

Ilford recommends not using pre-soaking: "A pre-rinse is not recommended as it can lead to uneven processing." See page 3 of the FP4 datasheet http://largeformatfilm.com/FP4-plus.pdf

Hi Pere,

You've mis-read and misunderstood Ilford's literature.

Read carefully:




It's okay - you wouldn't be the first student of photography to do so.

Ilford advise against pre-soaking in relation to rotary processors, which are continuously moving and increasing adsorption. This advice pertains to rotary processors.

Gabriel is not using a rotary processor.

This is because pre-soaking removes "in emulsion" surfactants that can be important.

Anyway a lot of people use pre-soaking without problems and (IMHO) also without any benefit. What is said to bring on problems is using a too short pre-soaking. So if you pre-soak then do it long enough.

...
I don't use presoaking..

The principles and reasoning given regarding surfactants on the emulsion as a rationale, also does not wash. Ilford's own literature states no such rationale, which goes against the principles of basic adsorption of a liquid onto a surface. If the surfactant is not removed from the surface of the film, it will never develop correctly.


RJ

[RJ-]

I'm getting all sorts of problems w my 810 negs, wanted to show a few to see what you all think. JPEGS 1 and 2 show one kind of problem, those lines of low and high density in the sky. #3 and 4 are riddled w fingerprints and crap, as if I'd dipped my hands in fixer before handling the negs (I didn't). Could this be a manufacturing defect?

Hi Gabriel,

Sorry to see this frustrating development issue.

At first glance, Images 1 & 2 appear to have film handling issues - most likely from hand loading out of the film box to make the exposure, and then to return the exposed sheet film into a box and before development, leading finger acids or deposits.

Image No.2 is interesting in the upper right field of the image, where a demarcated tone area of uneven development exists, suggesting uneven agitation in the tray, or Pyrocat HD exhaustion leading to localised development, realised by the impression of a corner of an overlapping sheet on its surface, instead of consistent development.

Image 3 & 4 appear to me as like chemigram photography - local finger print marks blocking developer contact intermittently.

Those are just impressions - perhaps the only conclusive way would be to trial the rest of the box using thin chemical free latex type gloves and developing tongs and clips from start to finish. Light leaks from your holders seem unlikely btw.

I've never experienced emulsion defects with Ilford FP4+ which to me is a trustworthy emulsion and production although have from Maco, Rollei in smaller 4x5 format.

Hope you get to the bottom of this.

Kind regards

RJ

[Pere Casals]

Hi Pere,

You've mis-read and misunderstood Ilford's literature.

Read carefully:

RJ,

Reading carefully ilford says: Dot, "A pre-rinse is not recommended as it can lead to uneven processing", Dot

IMHO the Ilford datasheet should clarify better because some professors were not understanding well the pre-rinse issues and missleading students.

Ilford could say:

> A pre-soak is totally unnecessary regardless of the method of development, if speaking about western films manufactured since 3 decades ago, at least.

> Many decades ago principal (western) film manufacturers designed films to not need pre-soacking at all. Surfactants are included inside the emulsion (not in the film surface) to ensure an even development. Pre-soaking washes out those surfactants, of course. Search ilford forum, there it is explained by competent people.

> A Pre-soaking won't harm with rotary processors, never, because instense agitation will prevent any kind of uneveness.

> With tanks and trays a short pre-soak may lead to uneven development.



So, rule of thumb, don't presoak.

...if you do it with tanks/trays then at least make a long enough pre-soak, and make a vigorous initial agitations to overcome the surfactants elimination.

A lot of Pro labs were not pre-soaking at all, and they knew what they were doing...

[Pere Casals]

If the surfactant is not removed from the surface of the film, it will never develop correctly.

RJ

Let me explain my view about that:

Surfactants are inside the emulsion (it's not an outer surface treatment), this allows the developer to penetrate inside the emulsion quickly and evenly, starting "induction" promptly.

During next 1 minute developer does not exhaust at all inside emulsion, because there is an "induction time" before development starts reacting with exposed crystals, so during this induction time the chem circulation-refreshment is irrelevant.

After the induction time passed emulsion should be softened evenly to provide an even chem refreshening and bromide evacuation. This is a design parameter for the used gelatin.

What hapens with a short pre-soak (tanks)?

IMHO, after the short pre-soak we can have a different emulsion softening in different areas, because different softening speeds: at the sides, near (35mm) sprocket holes, in the center... and we have the surfactants removed... so induction may start soon or later in different areas.

A long pre-soak won't harm perhaps, but film is designed to be processed without pre-soack, surfactants allow induction to start evenly, and gelatin is made to have an even chem difussion after some 1 min when real development starts and local developer exhaustion is a factor.

Sure a long pre-soak was a good advice 50 years ago when Ansel Adams was recommending that. Not today beacuse, as ilford says, it can bring on problems sometimes.

[koraks]

This thread makes me wonder if the surfactants are added to the emulsion to enhance even development, or if they are there for coating purposes.

For the record, with b&w, I never presoak any film or paper and get even development as long as my agitation regime makes sense.

[Pere Casals]

This thread makes me wonder if the surfactants are added to the emulsion to enhance even development, or if they are there for coating purposes.

For the record, with b&w, I never presoak any film or paper and get even development as long as my agitation regime makes sense.

Surfactant is a wetting agent, it decreases liquid (water) surface tension, so as developer starts entering in the emulsion then it is mixed with the wetting agent and it easily penetrates evenly and fast, so the differences between different areas are minor.

It is possible that surfactants have other applications in the film manufacturing, like improving coating operation and many others, of course.

Time ago there was a thread in the Ilford forum http://www.ilford.org.uk/cgi-bin/yab...;action=search about that, and IIRC an ilford techician was answering why ilford was dicouraging pre-soaking, now I cannot find it but he made clear to me the reason.

Perhaps we may ask ilford...

Addition: I've just asked it to ilford technical support. If they answer me I'll post it.

[Doremus Scudder]

The "to presoak or not to presoak" issue has been discussed extensively here and on APUG; so much so that we're really beating a dead horse here...

Ilford even contributed to one of the earlier conversations by clarifying (IIRC) that while a presoak was not recommended, it was not recommended against for most development regimes.

I presoak because I develop sheet film in trays by hand and without a presoak, the sheets would stick together. I presoak for a minimum of 3 minutes, usually longer. My developed negs are even and consistent. A too-short presoak can indeed result in uneven developing, so don't presoak or presoak long enough that evenness is not affected.

Best,

Doremus

[Pere Casals]

Doremus, I agree with you about presoak or not, and how long

...also I agree that they killed a horse, but that debate was technically inconclusive, at least what I had been reading sported poor reliable arguments, no mention to the induction time vs gelatin softening time, no mention about surfactants impact in the induction start, no mention about heterogeneous gelatin softening speed, no mention about AA era films vs modern films.

The single time I found a sound technical explanation was in that ilford forum, there an ilford technician (iirc) was giving accurate technical information.

I've asked Harman Technical Services if the reason they have to discourage the venerated pre-soak is surfactants wash out, let's see if they answer the question and what they answer, asking to people that has the knowledge is better than killing horses

[koraks]

Addition: I've just asked it to ilford technical support. If they answer me I'll post it.

Thanks, keep us updated. I know what a surfactant/wetting agent is and what it is supposed to do, and therefore, I can very well imagine that it plays a role in the film coating process. Still, it may be only there to enhance development; as a parallel, RA4 developers include a wetting agent as well (at least Fuji Hunt's does) which, I assume, is there to allow for even development given the short process times of RA4 paper. However, with film, such short processing times aren't customary and therefore, I wonder if a surfactant would be a logical addition to a film emulsion. It also brings up the question why no B&W developer formulas (film or paper) include surfactants (with the exception of collodion developers, which use alcohol in this role).

All this leaves some doubt if (1) the surfactant in Ilford films (assuming it's actually there, I haven't checked) plays a role in the developing process and (2) if the uneven development issues associated with inappropriate pre-soak regimes have anything to do with this supposed surfactant in the emulsion in the first place. Maybe - I just don't know. Let's hope Ilford gives you an answer.

Okay, one more observation from my end: I always use a fairly short (ca. 1 minute) pre-soak when developing C41 film, which really only serves to bring the tank and film close to the required temperature. I never get uneven development this way... Of course, you can't extrapolate this experience to a B&W film just like that. But still, I have a feeling that the issue with uneven development is virtually always idiosyncratic and therefore apparently caused by quite subtle differences in materials and processing parameters that we generally don't control for very strictly or are even unaware of. The conclusion? Figure out what works for you and stick with that. Experiences of others serve mostly to get inspiration for the kind of process parameters that may be relevant, but someone else's processing regime can't always be copied successfully. Maybe this even extends to the process suggestions/guidelines suggested by film manufacturers...

[Pere Casals]

All this leaves some doubt if (1) the surfactant in Ilford films (assuming it's actually there, I haven't checked) plays a role in the developing process...

koraks, my guess (say grounded speculation) is that a gelatin emulsion containing a wetting agent will get wet (with developer) way earlier and more evenly, so induction starts in all film areas at the same time, so practical developing time (after induction) is even.

Then if wetting happens uniformly, beyond induction start, also emulsion softening should happen at same time in all areas, and I also have the guess that the softening state should play a role about the amount of developer that's stored inside emulsion between agitations. Sure that a thinner emulsion (less softened) accumulates less developer and it can be exhausted earlier, and would contain a higher bromide concentration. Also a evenly soft emulsion should refresh developer inside in the same way in all areas...

This is what I concluded from my readings, sadly I cannot find the thread were a film manufacturing technician was explaining that, let's see if people at harman answer the question... just it would be interesting to know it for sure.