FOMA B&W film sheets - a question

BlueWind

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Can someone confirm that Fomapan 100 sheet films have any sort of chemicals on the film side opposite to the emulsion side ??
I got some pink discoloration on the border of my 13 x 18 negatives , in areas where the back if the film sheet may be stuck against the reel grooves.
Developer R09

 

thinkbrown

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I get the same pink discoloration on fomapan in 120 under the end tape. Haven't shot it in sheet but it seems likely it's coated the same way.
 

koraks

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Fomapan films have an antihalation dye embedded into the gelatin layer in the backside of the 120 and sheet film formats. It's green though on all the fomapan film I've seen so far.
 

thinkbrown

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It definitely rinses green but there's definitely a pink component to it in the base. I'll see if I've got a trimming sitting around to snap a picture of
 

koraks

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thinkbrown said:
It definitely rinses green but there's definitely a pink component to it in the base. I'll see if I've got a trimming sitting around to snap a picture of
Click to expand...
The end tape on 120 goes over the emulsion side, not the base, unless you fold it over after removing the film from the backing paper. In that case it may cover both sides. If you tear it off and leave only the part that's originally on the film, then what you have underneath it is the emulsion side, not the backside. This will have the color of the silver halide emulsion, which tends to be creamy and can have a magenta tinge due to the presence of spectral sensitizing dyes. It's been a while since I processed Fomapan roll film and I don't recall exactly what the emulsion looks like on that product.


Anyway, refer to this thread: https://www.photrio.com/forum/threads/fomapan-100-what-gives.185354
I think it's a dye in the actual emulsion and it'll probably wash out with a prolonged alkaline and/or sulfite wash.
 

thinkbrown

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koraks said:
The end tape on 120 goes over the emulsion side, not the base, unless you fold it over after removing the film from the backing paper.
Click to expand...

That's exactly what I do haha. I'll double check and see if I can confirm the side next time I process a roll
 

koraks

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thinkbrown said:
That's exactly what I do haha.
Click to expand...

Hey, there's a reason I thought of that option, haha!

Anyway, looks like there's a magenta dye thing going on with relatively recent production Fomapan. I haven't experienced it yet, myself, but the thread I linked to does give some clues as well as confirmation that it's there.

In general, magenta dyes in film tend to wash out, sometimes with some difficulty. They're pretty omnipresent; you get them in Kodak and Ilford B&W films and also in color negative films. Whether it's always the same kind of dye, IDK, but I wouldn't be surprised if they're all the same or at least closely related.
 

thinkbrown

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Found a scrap. It's doesn't seem like the same type of dye I get in other films because it appears to go away before I get to the rinse step, vs something like tmax where the water rinses pink for ages.

Worth noting that this roll of foma expired in early 25 so it's not an especially new batch.
 

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BlueWind

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Thank you for your answers. So the FOMA sheet has indeed an anti-halation layer on the backside.
That may be related to the stains I have found. I will change the protocol to ensure that more water reaches that part of the film (before and after the development). If necessary I will do the fixing and final rinsing in trays.
I don't know if I should try any form of physical removing (rubbing? scrubbing) those stains...
Regards
Joao
 

koraks

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thinkbrown said:
Found a scrap. It's doesn't seem like the same type of dye I get in other films because it appears to go away before I get to the rinse step, vs something like tmax where the water rinses pink for ages.
Click to expand...
It's interesting though since your sample shows very nicely the green anti-halo dye on the backside as well as the (I think new) magenta dye on the front/emulsion side!

BlueWind said:
I don't know if I should try any form of physical removing (rubbing? scrubbing) those stains...
Click to expand...

No! It won't help and it'll just damage your film. The magenta is on the image side of the film. It's a dye that's embedded in the emulsion. I remember now that the solution should be to soak the film for a few minutes in a fairly strong solution of ethanol; something like 10-30% v/v at least.
 

ic-racer

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Try a prolonged water soak. Maybe more than 30 min. Anyway, that is what works for me.
 

Alan9940

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I've always had good luck with HCA removing any last traces of anti-halation dye.
 
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BlueWind

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Thank you for your replies, but I think I have solved the problem.
Four exposed 13 x 18 negatives in a reel in a daylight Patterson tank, using R09 one shot. Prolonged pre-wash, development as usual, stop bath with tap water as usual. Then two negatives were kept in the reel and two were placed on a tray . Ilford rapid fixer in the tank and in the tray. Five minute fixing in both cases. Stains persisted in the reel-fixed negatives and were absent on the tray.fixed ones !!!

I will confirm this result once more and will change my darkroom protocol.

Another question arises related to tray-fixing : can I do it under a weak red safelight or should I fix in total darkness ???

Thank you again

Joao
 

retina_restoration

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Any sheet film processing technology that holds the film stationary in a reel or clamp holder tends to impede the chemistry’s ability to neutralize or leach out the anti-halation dye. As you’ve discovered, the solution is to either fix the film in the tray or avoid using the film holder style technology altogether. I must admit, I’m biased in this matter. I’ve never used any technology other than trays for processing sheet film (and likely never will), so I speak from my personal experience and preference.

As for fixing, you can fix in trays with a light on, as long as development has been stopped completely by using an acid stop bath (not just water).
 
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