Image stain and general stain

[swmcl]

Hello all,

I wish to try to understand the ideas around image and general stain.

To my mind, as the film is developing in the staining developer solution, a stain develops in and around the image parts as these parts are most sensitized for development. As development proceeds if conditions are right (eg. too high pH, too much oxidation, too little chemicals to prevent aerial oxidation ... etc.) then the staining action goes too far and it occurs over the whole of the film including out-of-image areas. Its not as though the staining action stops in the image area at some point its just that it goes too far and proceeds onto the film in general.

So general stain is bad because you have to print through it and it is also possibly somewhat inconsistent. ie. some parts of the film are more affected than others.

The idea is to allow stain to develop but only to the point where staining in general starts to occur and no more. At this point one might consider a negative to be 'maximally stained'.

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Have I got it right ? Is this how it happens ? Is it absolutely true that a negative that has general stain is badly compromised ? Could one develop negatives to the point where stain is visible and be assured they hadn't damaged the image itself ?

Please offer your corrections if I am wrong. That is what I'd like to see.

Cheers,

 

[Rudeofus]

AFAIK stain forms whenever oxidized Pyrogallol crosslinks with the gelatin. Since it appears to do this rapidly, Pyrogallol oxidized by developable silver halide will stain the negative right where development happened, and people call this image stain. This is the stain which is claimed to do all the good things, amplify the image, reduce grain, whatever.

Contrary to that, aerial oxidation of Pyrogallol doesn't require any developable silver halide, therefore it happens wherever Oxygen meets Pyrogallol, and stain will form right there. Assuming you have an even distribution of both Oxygen and Pyrogallol across your film sample, this sort of stain will manifest itself as more or less homogeneous density. You should be able to print through this extra stain, but perfectionists that many of us are, we'd rather not have it.

Note, that regular image fog (silver halide grains which developed without having seen an intentional exposure) will also create stain, so it can be difficult to distinguish between stain from aerial oxidation and stain from fog.

 

[CropDusterMan]

For quite a while, I did the second bath in the used developer with PMK Pyro and although I no longer do it, and am aware that Gordon Hutchings no
longer advocates doing such, those negative are still wonderful to print. I don't notice much difference in terms of excessive stain affecting print times
contrast or acutance.

 

[Gerald C Koch]

Michael is right non-image stain and image stain form at the same time. It is preferable to keep non-image stain to a minimum. Doing so is tricky and requires the right balance between preservative (sulfite or ascorbate) and staining agent (pyrogallol or catechol). It also depends on keeping aerial oxidation of the staining agent to a minimum.

One of the points usually missed by people fond of very dilute developer solutions is that not only is the amount of developing agent reduced by dilution but also the amount of preservative. When you use these very dilute solution greater than 1:100 you effectively change the entire character of the developer. At a certain point the dilute developer becomes unstable and it is no longer possible to keep the developer for more than a few minutes. It is possible for the developer to not even last for the entire development time.

 

[Vaughn]

For quite a while, I did the second bath in the used developer with PMK Pyro and although I no longer do it, and am aware that Gordon Hutchings no longer advocates doing such, those negative are still wonderful to print. I don't notice much difference in terms of excessive stain affecting print times
contrast or acutance.

I no longer use a 'staining bath' after fixing (I was using Rollo Pyro in drums). I noticed with Bergger 200 (spelling), that there was a greater general staining than some other films.

 

[DREW WILEY]

It all depends on the specifics (exact film, developer, method of development). If you used automated drums you need to used a pyro formula compatible with that method, so you don't get excess aerial oxidation with high overall fog. There are also two unrelated categories of pyro: pyrogallol vs pyrocat, which yield different color images stains and affect their behavior in that respect, not to mention dozens of different tweaks of both options. The early PMK literature did recommend an alkaline afterbath, noted by Vaughn above. It appears to have been a redundant step which merely increased overall fog. I don't know of any true "thick emulsion" films still on the market, but some films do stain more heavily than others.

 

[swmcl]

Thanks guys,

I'm not using a technique to re-introduce the film to the used developer. Just a simple straight-ahead process. One thing after another not re-using chemicals. Pre-wash using distilled, develop using distilled, plain water wash x 2, fix in TF5, plain water wash with many changes and my latest trick is to not use PhotoFlo at the end on sheets. I used to use a very weak citric stop and I am undecided on Lavaquick and Adostab. My process is getting simpler.

Basically I take these thoughts,
- Back off on the accelerator or indeed change the accelerator if the general stain is too high (assuming both the agitation method aint changing because it can't get any slower and neither can I change a stock solution ...) My first sheet with carbonate was a wicked green so the next is with a metaborate.
- An amount of general stain isn't too detrimental to the printing process but should be avoided and minimised.

I see in some notes on PMK that carbonates are best for pyrocatechol and sodium metaborate for the pyrogallol. So I'll spin up a test with my new potion and some metaborate soon.

I'm thinking a 1:2:100 mix. I've made a stock solution with 300g metaborate into 1 litre as my Part B.

There are some different formulae for PMK I think and one of them is using a pretty stiff brew of metaborate (did I see 600g into 1400ml ?) at 3:100 I think. I'll tone it down for my first test and try to remember to take a pH reading just before I add Part A.

The stain on my sheet that came out green previously seems to have changed a bit toward a brown and the stain may have faded. All a bit subjective if I don't measure it I guess. But .. here's a question ... do the different stains (pyrogallol vs pyrocatechol) change over time and how sensitive are they to UV or IR ? I did read they were sensitive so I'm not asking if they are but more how much they are sensitive ...

Cheers,

 

[Shawn Dougherty]

The stain on my sheet that came out green previously seems to have changed a bit toward a brown and the stain may have faded. All a bit subjective if I don't measure it I guess. But .. here's a question ... do the different stains (pyrogallol vs pyrocatechol) change over time and how sensitive are they to UV or IR ? I did read they were sensitive so I'm not asking if they are but more how much they are sensitive ...

Cheers,

I have been reading a bit on this and meaning to start a thread. It seems to deserve it's own so I have started one:
(there was a url link here which no longer exists)

Thanks you.
Shawn

 

[Doremus Scudder]

...

The stain on my sheet that came out green previously seems to have changed a bit toward a brown and the stain may have faded. All a bit subjective if I don't measure it I guess. But .. here's a question ... do the different stains (pyrogallol vs pyrocatechol) change over time and how sensitive are they to UV or IR ? I did read they were sensitive so I'm not asking if they are but more how much they are sensitive ...

Cheers,

My experience with PMK: The stain will "evolve" over the processing time, increasing a bit during the final wash even, and changing color a tiny bit as the negatives are drying. After that, I've found the stain to be very stable as long as the negatives are stored well and away from light. That said, I even have a couple of negs that were pinhole tests that have been sitting around in a window sill in the kitchen for a couple of years and which look just the same as they did the day they were developed and are just the same color as the other well-stored negative. I'm not too worried about my negatives fading before I'm not able to print them any more...

Using a sulfite-based wash aid on PMK negatives will remove stain and change its color. I've also found that selenium toning negatives (which I did earlier to intensify them somewhat) will remove the stain also. I've switched to bleach/redevelop for intensifying the odd negative now (more later). There may be other things that will affect the stain as well. I now develop, acid stop, double fix and wash only.

As for stain color: I've found that my negatives processed in Vienna (Austria) using the tap water are slightly greener than my negatives processed in Eugene, Oregon with the tap water there. I'm not sure what causes this; the chemicals are identical (PMK kits from Photog. Formulary) and the developing times are within 30 seconds of each other. I do find that the PMK is a bit more "active" in Vienna due to the harder water. It could be that this extra bit of calcium carbonate in the tap water somehow affects the pH or buffering a bit and, therefore, the stain color as well. In any case, the negs all print well, so the slight color shift makes little difference, if any.

You don't say how you are developing, but if you're using rotary processing, which tends to produce a great degree of aerial oxidation, you may be better off with Rollo Pyro (with ascorbate added) than the PMK formula. Also, you seem to be formulating your own developer or at least tweaking PMK. You should realize that both PMK and Rollo Pyro were years in the making, and their formulators optimized the formulae time and time again to optimize the balance between image and general staining (the same applies to Sandy King's Pyrocat). You may not find a much better solution than what has already been achieved.

FWIW, I use bleach/redevelop from time to time to intensify weak negatives. I bleach in a ferricyanide/bromide rehalogenating bleach and re-develop in PMK. The resulting stain on these negs is more intense and more yellow-green than the "army green" of my usual PMK negs. As an aside, the technique works really well for getting about a Zone more contrast from a negative and provides a bit of extra shadow detail as well.

Best,

Doremus