Stain on Kodak Technical Pan

I am experimenting with Kodak Technical Pan. After processing it using C-41 colour developer and fresh Ilford Rapid Fixer I got a fairly dense pink/magenta stain (see the picture). I thought the problem was with insufficient fixing discussed in this thread:


I did another test and fixed a blank piece of film (in daylight). The film cleared in 25 seconds and I fixed for 2 minutes. I got the same stain as with the C-41 developer. I thought it was some stubborn antihalation layer so I washed the strip in baking soda. The stain turned brown-yellowish and became lighter. To quickly dry the film I washed it in ethanol. This removed most of the stain. Some still remained near the edges.

Previoiusly, I made a step wedge on Technical Pan and processed it in Barry Thornton's 2-Bath developer. My fixing time was about 3 minutes. There is no stain (see the picture).



Top: undeveloped fully exposed film, fixing for 2 min; water wash; baking soda wash; ethanol rinse
Middle: C-41 colour developer; about 2 min. fix; water wash
Bottom: BT Two-Bath developer; ~3 min fix; water wash


I checked the datasheet for this film and there are no specific requirements with regard to fixing.
Is it fixed insufficiently? If so, does the "twice the clearing time" rule apply for this film? How long should I fix it for?

So, looks like an anti-halation dye issue. The thing with these dyes is that it depends a bit on the developer how easily they wash out in subsequent processing. Maybe it's the high amount of sulfite in the first Thornton bath that helps to clear the dye very effectively. C41 developer doesn't have much sulfite at all, so wouldn't have this 'feature'. There are plenty other differences of course.

In any case: (1) anti-halation dye clearing does not only depend on fixing. (2) Clearing or lack thereof of the anti-halation dye doesn't say much about the completeness of fixing. Remaining dyes are not necessarily indicative of remaining silver halides. (3) doesn't matter much how you clear the anti-halation dye as long as you get rid of it to your satisfaction. If it takes an additional extended wash, a rinse in ethanol, a soak in a sulfite bath or whathaveyou; just use whatever is convenient to you.

Thank you for the reply.

koraks said:

looks like an anti-halation dye issue

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The thread that I mentioned confused me. It was not clear if the dye was an anti-halation layer on the non-emulsion side of the film or the sensitising dye added to the emulsion.

koraks said:

it's the high amount of sulfite in the first Thornton bath that helps to clear the dye very effectively

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I agree. I noticed that it dissolves the antihallation layer very well. Unfortunately, after I processed Verichrome Pan (pinkish) and Foma (greenish) the solution took some indeterminate colour and I could not notice any change after processing Technical Pan. Same with the colour developer, it is nearly exhausted.

koraks said:

Remaining dyes are not necessarily indicative of remaining silver halides

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Fixing vs. dissolving the dye was another confusion after reading the thread. My understanding is that removing the dye is a side-effect of prolonged fixing. Extending fixing time solely to clear the dye sounds like a bad idea to me.

koraks said:

doesn't matter much how you clear the anti-halation dye

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Sulfite bath seems the most practical option. Some people suggest soaking instead of extended washing in running water (or extra rinses in Ilford method). That could also work. Ethanol would be too expensive, even when diluted and reused. Any suggestion on the concentration of sodium sulfite? Bath A uses 40g/L and we know it works.

I have a 12m roll of 70mm Technical Pan. I never worked with this film before and would like to nail my processing before I go and start shooting it.

N

Romanko said:

Extending fixing time solely to clear the dye sounds like a bad idea to me.

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Not necessarily; there's no real penalty for fixing longer than necessary. You'd have to go for an outrageously long fixing time to get you into any trouble at all. It's mostly just annoying to have to sit and wait for it to finish, so I generally try quicker methods instead.

Romanko said:

Any suggestion on the concentration of sodium sulfite?

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I'd go for a seat-of-the-pants approach and take a convenient amount of water and then teaspoon some sulfite into it. For me that would probably be a volume in the range of 500ml to which I'd likely just toss one teaspoon to begin with and then add some more if things don't go as fast as I'd like.

Romanko said:

would like to nail my processing

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This is not a very critical part. If the dye doesn't clear, just throw some generic chemistry at it to solve the issue. There's a lot you can do without harming the images in any way. I wouldn't worry about it and shoot whenever/as soon as convenient.

koraks said:

toss one teaspoon to begin with

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That should do the trick. Will try this tomorrow and report the results.

koraks said:

I wouldn't worry about it and shoot whenever/as soon as convenient.

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I am still not sure if I would be able to tame the contrast of this film and if I like the look of it. The first test shot was not too bad but it was a low-contrast scene. I don't want to spend too much time doing sensitometry and strip tests of the expired and discontinued technical/document film. At some stage I'll have to draw a line and start shooting anyway.

Yeah, I see what you mean. Well, liberal exposure and somewhat arcane, low-gamma developers would do the trick. But you're on that track already by the sound of it. Can't help you with this part as I've never shot Tech.Pan. TMAX is similar in terms of the dye issue though and I used to shoot that frequently in 4x5. It did indeed clear only with relative difficulty.

Romanko said:

The thread that I mentioned confused me. It was not clear if the dye was an anti-halation layer on the non-emulsion side of the film or the sensitising dye added to the emulsion.

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A anti-halation means (not even necessarily being a dye) not necessarily must be located in the back of the base.
Even technically more advanced was the Agfa approach on placing it in front of the base.

AgX said:

placing it in front of the base

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Thank you AgX, I always learn something new from you.

Today I made another step wedge and processed it in C-41 colour developer for 19 minutes at 20 degrees Celsius. The film came out with clear base without any sign of stain. The only thing different from the test strip (see the picture in the first post) is agitation. This time I used 30 s initial agitation followed by 10 s agitation at 4, 8, 12 and 16 minutes. I looked at the film after fixing it for 2 minutes and it was clear (no stain). I fixed for another 2 minutes.

So the problem seems to be my test strip method. I have a small lifting platform with a lab stand on top. I attach a strip of film to a glass stirring rod held in a clamp of the lab stand vertically. I lower the strip into the bottle with the developer to a specified depth (at 5 mm increment) at required time intervals (3 minutes). With this setup I cannot provide adequate agitation. Rocking the bottle after each step seems to be insufficient. Next time I'll try separate strips of film (one for each step) and develop in a tray/dish. That way I can be more consistent with agitation.

In any case, C-41 seems to do the trick of controlling the contrast of the film. I am happy with the results. Thank you koraks and AgX for your advice and encouragement!