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Developing Fomapan 100R - replenish bleach or replace?


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#1 Marc Roessler

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Posted 30 October 2010 - 01:45 PM

Hi,

I'll be developing two rolls of 16mm Fomapan 100R in a lomo tank in a few days. I've got the Foma Reversal kit which suffices for development of these two films (2x 30,5 Meters). The kit will give me 1.6 liters of processing solution. The tank requires 1.8 liters for one batch (i.e. 30 meters of film).

I need to thin the solution to 1.8 liters (1.6 is not enough, I tested this). Usually development time is 12 minutes. How should I extend the development (and bleach, and fix..) time to account for this? Last time I used 13.5 Minutes instead and this seemed to somewhat work, but I'd love to know the relationship between concentration of the developer and development time. Is this a linear relation? I.e. half the concentration, double development time? I'm sure it's not that simple..?

Then there is the issue of the bleach. The Foma kit comes with sulfuric acid/permanganate bleach bath. The permanganate will no doubt oxidize until I can process the second film (directly after the first one, but no doubt too long...). I see two options:

A
before processing the second film, replenish the bleach bath with fresh permanganate (including filtering etc..). The question is how much to replenish (fully?) and if I also need to replenish sulfuric acid (don't have any of that handy).

B
set up a fresh bleach bath with potassium permanganate and sodiumbisulfate (NaHSO4). The bisulfate I have is industry grade (swimming pool ingredient) so there's the question if that's pure enough, and even if it is pure enough if this mix will work as well the original mix from Foma with sulfuric acid.

Any experiences here?

Thanks,
Marc

Edited by Marc Roessler, 30 October 2010 - 01:50 PM.

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#2 K Borowski

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Posted 30 October 2010 - 03:06 PM

You're using a rewind tank, right? If so, oxidization of processing solutions makes it a bad idea to try to replenish. With this method of processing, it's best to use solutions in a "one-shot" configuration.

Also, consider the small amount of solution, about a half a gallon (~1.8L) processing two hundred-foot rolls (~61m) of 16mm film. You get to a point where the actual amount of solution that is used up by processing that much area of silver halide film is so high that replenishing it is MORE expensive than just throwing it out.

Processing machines that can be practically replenished are often more than 4+ U.S. Gallons (15+L) where oxidization is minimal compared to the total volume of chemistry.

The smaller amount of solution, the greater surface area, the less practical it becomes to replenish chemistry.


Professional motion picture processors (considered "small" by this industry's standards) are 50+ gallons (190+L) per tank, which is minimally impacted by running a couple of rolls of film through. Every time they run film, they almost immediately dump a certain amount of tank solution, and replace it with over-concentrated replenisher, which "regenerates" the partially-exhausted tank solution.

Hope this helps.
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#3 Charles MacDonald

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Posted 30 October 2010 - 07:02 PM

You're using a rewind tank, right? If so, oxidization of processing solutions makes it a bad idea to try to replenish. With this method of processing, it's best to use solutions in a "one-shot" configuration.


The Lomo Tanks are a spiral tank, not a rewind job. Doing your own processing was part of the fun in the old Soviet system.

I am not sure of there is ANY relationship when you dilute the chemicals, as the PH would change. I wonder if FOma might have a tech buletin on this - they have undoubtedly encountered the problem as those Lomo tanks are quite common in the former eastern block
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#4 Marc Roessler

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Posted 30 October 2010 - 07:44 PM

The Foma processing kit is 20 Euros (about 28 Dollars). Replenishing the bleach with 4 grams of permanganate is about 50 Cents, doing a completely new bleach mix with Disulphate and Permanganate is about 2 Euros maybe. I agree that replenishing the other processing solutions is probably not economical, but I didn't talk about that, just the bleach bath.

I'm a bit reluctant to dump perfectly well processing chemicals, generating unnecessary toxic waste... as Foma states, the baths are sufficient for 2 100" rolls. The only problem is that the bleach will oxidise until the second batch. This is why I would like to replenish (or re-mix from scratch) the bleach bath only.

It is the lomo spiral tank, as Charles wrote. The morse rewind tanks.. well I just think they're a bad design.

Marc

Edited by Marc Roessler, 30 October 2010 - 07:45 PM.

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#5 K Borowski

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Posted 30 October 2010 - 09:14 PM

Sorry, I was mixing up the Lomo with the Morse. I have a Morse, and it is perfectly fine for B&W, though time-consuming.

So, you're unhappy that I am talking about all processing chemicals, not just the bleach? OK. . .


If it's just bleach you want to re-use, you can just extend the bleach time instead of replenishing, until you reach capacity of the solution.
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#6 Marc Roessler

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Posted 31 October 2010 - 06:07 AM

Thanks Karl!

This leads me to the next question: how critical is "over bleaching"? I know that Fomapan has a soft emulsion and that care will need to taken here, but how critical is this seen from a purely chemical view?

I more or less tend to try the disulphate bleach, first testing it for chlorine ions (using the silver chloride test) that may be present due to the technical grade quality disulphate.

For reference, in case others read this thread:
Concerning replenishment of bleach I found in Friedrich/Meier's "Filmhandbuch" (a book on movie film lab chemistry) that only the bleaching agent (in their example: chromate) is consumed. The acid is only needed for getting the necessary pH value as a setting for the reaction to take place. I.e. as long as not too much water or alkaline components are introduced from the previous baths, the acid does not need to be replenished.

Marc
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#7 K Borowski

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Posted 31 October 2010 - 12:16 PM

I don't have a BS in Chemistry, sorry.


I know the solution has to be acidic, but I've never bothered to test the pH, as I am bleaching to completion. You can bleach by inspection in a Morse, with the little window on the front, so I usually follow this approach.

I would say that, as a start, you want to increase 10-20% on the bleach time with each subsequent run. I don't know how many runs you can get away with, but I wouldn't go past using that same solution more than 4 times.


You are not going to have the acid eat through the emulsion or the film base, no. I've used the standard R-9 bleach, potassium dichromate and sulphuric acid. There are very small amounts added to a large batch of water, only a few spoonfuls per U.S. gallon. I've had to stick my bare hands in the solution occasionally, when film becomes detached from a rewind wheel during the process, and it would only sting if I had a cut on my hand.

So, if you are using something similar, it's quite dilute (low molarity), so as long as you don't dump 100g of sodium hydroxide in it accidentally, it should remain sufficiently acidic from use to use.

As far as dichromate, or in your case disulphate, ions, there are figures available online for how much silver is in a 100-foot roll of 16mm film (check Kodak tech pubs to start if you can't find Foma figures). Silver chloride, bromide, and iodide molecules I'm not sure will react differently from one another, but figure that, with B&W, you generally only remove about half of the silver on the film (slightly less with reversal, as the unexposed edges are fully developed).

If you want to figure that out in terms of a chemical reaction, you can, but I think that is generally unnecessary. You can always just replenish, if you do figure it out, by adding water and disulphate to bring the volume and concentration back to standard after each run, although the buildup of halides will probably still slow the bleach time.


It really is best just to bleach by inspection! Take the reels out of the tank after the standard bleach time, peel off a few turns of film, inspect, and go from there.
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#8 Marc Roessler

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Posted 31 October 2010 - 12:45 PM

you're brave Karl.. dichromate with bare hands and a cut on the finger :ph34r:

Just checked my disulphate, it contains traces of chlorine ions when dissolved in distilled water. Not so good, so I'll go with reusing the original bleach bath.

Bleach by inspection sounds very good... what is the starting point where no ill effects can be observed on the film when exposed to light? After rising the first developer? After a major portion of the bleach bath has completed its work? I know that you re-expose (to light) after the bleach bath, but you don't re-expose (chemically) to the bleach bath after that again.. so is this safe to check bleaching "in progress" or does one have to take care here?

The (potential) issue with the emulsion peeling off is not because of the bleach itself, it's more because the Fomapan emulsion is quite soft from the start, so having the film in processing solutions for about an hour total (with wild pH changes) is critical already. (That's what I found on the net from others doint a reversal process on foma 100R). That's why I'd like not to dramatically extend bleach time.

Thanks,
Marc

Edited by Marc Roessler, 31 October 2010 - 12:48 PM.

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#9 K Borowski

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Posted 31 October 2010 - 01:45 PM

you're brave Karl.. dichromate with bare hands and a cut on the finger :ph34r:


Well, I don't do it on purpose. I didn't know I had a cut, and the film came off one end of the rewind in the tank, so I had to reach in and re-attach it. Without a cut, I have observed no ill effects from placing my hands in bleach. Of course, I do wash them afterwards B)

Just checked my disulphate, it contains traces of chlorine ions when dissolved in distilled water. Not so good, so I'll go with reusing the original bleach bath.


Not a full-fledged chemist, but wouldn't that be from the acid being in solution? Are you using disulphate and HCl, or some other combination? What is the formula?

Bleach by inspection sounds very good... what is the starting point where no ill effects can be observed on the film when exposed to light? After rising the first developer? After a major portion of the bleach bath has completed its work? I know that you re-expose (to light) after the bleach bath, but you don't re-expose (chemically) to the bleach bath after that again.. so is this safe to check bleaching "in progress" or does one have to take care here?


It's been a while.
First dev.
Stop
Bleach
Clearing Bath
Chemical or Photographic Re-exposure
2nd Dev
[Optional Fixer]
Wash & Stab (Photo-Flo or other agent)

Are those the steps you're using? May have missed a few intermediate water washes. Anyway, as long as you aren't using bright light, after the stop you should be fine. Better to wait until the bleach has been done for the standard time before going in to inspect, at the very least thirty seconds into the bleach before pulling out the film to inspect.

With a spiral tank, unlike a rewind, you'll have more difficulty seeing when the black metallic silver is completely removed and only halide remains. Back-lit, the silver negative areas will be clear base or partially milky, and the reversal areas, undeveloped will be milky white or appear dense lit from behind.

The (potential) issue with the emulsion peeling off is not because of the bleach itself, it's more because the Fomapan emulsion is quite soft from the start, so having the film in processing solutions for about an hour total (with wild pH changes) is critical already. (That's what I found on the net from others doint a reversal process on foma 100R). That's why I'd like not to dramatically extend bleach time.


The film emulsion is subject to PHYSICAL abrasion, sure, but it is DESIGNED to go through this process. R-9 bleach et al are designed to bleach out METALLIC SILVER ONLY, not halides, gelatin, acetate, or anything else. I would assume it attacks other metals, but that is immaterial here.



That's all I've got. Good luck!
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#10 Richard Tuohy

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Posted 31 October 2010 - 06:30 PM

Hello Marc,
few things. the bleach process is 'too completion'. You can't realistically over bleach. Leave it in for 3 minutes and it will be well and truly done. The permangenate bleach will be fine for a second film processed in the same session. If you are diluting the bleach to make up volume, leave film in longer. While you don't use a stop bath for the black and white reversal process, if you use a very good and long wash, you can turn the lights on after the first developer without effect. But it does have to be a very good wash to make sure there is no developer left on the film. That said, there is no need to do that. After a minute or so in the bleach (wont matter just how long), turn the light on and pull the spiral out and have a look to see if there is any silver left on the film. The silver is black. Of course, it is better to re-expose to light with the film in a water bath so as to ensure the light hitting the film isn't' being focused by little spots of water, but if you have to check, just check.
If you have to dilute the developer, then do so, but just as little as possible. Does the Foma kit provide for a separate developer solution for first and second dev? If so, pinch some second dev to top up the first (as long as its actually the same developer formula that is ... it may be a different developer).
good luck,
rt
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#11 Friedemann Wachsmuth

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Posted 02 November 2010 - 02:54 AM

There is a simple, yet effective way to make Potassiumpermanganate-based bleach last for months instead of minutes. This is absolutely worth it considering how insanely toxic dichromates are. So how?

FIrst of all, use demineralized water for both parts (the acid and the permanganate). This is important, since the latter does react with traces in normal tab water quickly. With this tweak only, the two solutions poured together last many hours instead of minutes. If you add 20g M19 (Photo-Calgon, Sodiumpotassiumhexametaphosphate) oer Liter of mixed solution, it works for many months. This is from an old Agfa Patent EP 1006408 B1, so worth a try :)

The Foma Kit is such a rip off.
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#12 Marc Roessler

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Posted 02 November 2010 - 02:53 PM

Friedemann, cool tip, thanks!

I used distilled water already, but still had the problem of manganese dioxide forming after some time. Does the calgon work against oxidizing?

I developed the two rolls yesterday, used 1800 ml instead of the 1600 ml for all baths, same processing times. Filtered the bleach solution before use. Worked like a charm. For the second film's bleach bath I added 3 grams of permanganate for replenishment, let stit for 15 minutes, and re-filtered it before use.. lots of manganese dioxide in the filter, again, so this tells me the replenishing was not an entirely bad idea.

After I had processed the two rolls I remembered that I still had a short end of 7213 (Vision3 200T) sitting around, so I shot these 12 meters in my bathroom. I developed with the used developer, quickly threw together a stop bath from vinegar (balsamico works great...) and distilled water and fixed in the used fixer. It worked! The negative still has the orange masking of course, but you seem to get a usable image. I developed for 12 minutes, this seems to result in a slightly higher EI then the usual 200. Difficult to judge without a densiometer or scanner or 16mm printer though.

Wanted to attach an inverted scan of the neg, but unfortunately I seem unable to upload any images, as the board claims I exceeded my upload quota. As I can't find how to delete any previously attached images, I'm SOL...

Greetings,
Marc

Edited by Marc Roessler, 02 November 2010 - 02:55 PM.

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