Interesting advantage of C-41 kits with separate fixer + bleach: Easier disposal.

I was just watching YouTuber Shaka1277's review of a particular C-41 kit, and he said something that caught my attention (link):

Any fixer, once used, will have dissolved silver salts in it. That makes it a hazardous waste that has to be disposed of at your municipal waste disposal facility. You can get around this by using the steel wool method to de-silver the fixer. Iron salts replace the silver salts, and the silver turns into metallic silver, coating the steel wool. The de-silvered fixer is safe to pour down the drain and the solid steel wool with silver coating can be tossed in the regular trash.

This doesn't work if your C-41 kit uses blix: The purpose of the bleach is to take metallic silver and convert it back into ionic silver. So it won't let the silver stay on the steel wool.

I thought that was interesting.

Interesting, and also correct.
The bleach is a bit of an issue due to the ammonium bromide, which is apparently nasty.

Things a slightly different if you take the used chemistry away for disposal to a dedicated facility. There it depends on the nature of the disposal process if it's still beneficial to have separate bleach & fix.

It's also different for large-scale labs since desilvering and regeneration of blixes is perfectly feasible and indeed commonly practiced (for paper; no high volume film blixes are used AFAIK).

dcy said:

This doesn't work if your C-41 kit uses blix: The purpose of the bleach is to take metallic silver and convert it back into ionic silver. So it won't let the silver stay on the steel wool.

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Well, that's sorta true, but doesn't the blix eventually become "exhausted" such that it can no longer "bleach" the metallic silver? How do you resolve this question?

One significant reason that a moderately-sized commercial lab would not use a film blix is that it's much easier to recover silver from fixer than from a blix. It's sort of a trivial thing to electrolytically recover a high proportion of one's silver from a fixer (assuming that one possesses purpose-built equipment and knows how to use it). The electrolytic silver gives a "known quantity" of high purity silver flake, meaning that 1) silver refining charges are pretty low, and 2) it's hard for a "questionable" (I'm being polite here) refiner to take advantage.

Note that this "desilvered" fixer is still not ready for disposal cuz there's still significant silver in it. Electrolytic desilvering can typically only get down to around 100 mg/L silver; some sort of "tailing" method would ideally be used.

A second significant reason that a moderately-sized commercial lab would not use a film blix is that it can't be "regenerated." With a pure C-41 bleach it's possible to collect the process overflow (from a replenished system) then add a regenerator package, essentially converting a waste product back into a replenisher.

Here, for home users it goes down the sanitary sewer. No biggie.

Small labs use a cartridge of steel wool for the trickle that comes off the machine, effluent then goes to sanitary sewer.

Depends on where you live. In Iowa we have access to so many resources and have so few people it's not a problem

Runoff from Big Agriculture is another thing. Huge problem!!!! Over application of nitrogen fertilizers, some liquid animal waste from swine and poultry.

State is pretty much controlled by the lackeys of the agricultural concerns. Of course I live in "The People's Republic of Johnson County" beautiful place. No hogs except for a few living outside and in shelter. Old school

dcy said:

Any fixer, once used, will have dissolved silver salts in it. That makes it a hazardous waste that has to be disposed of at your municipal waste disposal facility.

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That's not really ALL true, at least in the US.

The US has a law known as RCRA, which by definition can make a silver-bearing solution become a so-called "Hazardous Waste" (assuming that the law has not been changed since I last had involvement). The number, as I recall, is something like 5 mg/l silver. Now, there are other details, including probably a small-user exemption. At any rate, as i recall, RCRA only comes into play when you remove the "waste" from your facility. So if you can treat it within your facility, AND if your POTW (publicly owned treatment works, the sewage treatment plant) is willing to accept your effluent then RCRA doesn't come into play at all. So it doesn't formally become a so-called Hazardous Waste. As a small user in the US you can probably, more than likely, just dispose of your "silver-bearing solutions" down your municipal sewer. But... verify via local laws and regulations first.

It probably sounds like I'm just playing with semantics, but... in a number of studies I've read, photographic silver has never been shown to be especially "Hazardous." (By photographic silver I mean silver thiosulfate, as in fixer.) The general gist is that in silver thiosulfate the silver is so tightly bound that only vanishing small amounts exist in ionic form (Fwiw this is a main reason why it is difficult to electrolytically recover silver.) Earlier US EPA documents, circa 1980 say that silver thiosulfate is something like 10,000 to 30,000 times less toxic to microorganisms than silver nitrate, for example. Later studies indicate that, when photographic silver gets into a sewage waste stream, it soon ends up as silver sulfide, which is considered VERY stable.

FWIW I'm a proponent of recovering one's silver as much as can be justified. But I'm real skeptical that local "municipal waste disposal programs," where people bring in their household "Hazardous Waste" have much value related to disposing of used photographic fixer.

Mr Bill said:

That's not really ALL true, at least in the US.

The US has a law known as RCRA, which by definition can make a silver-bearing solution become a so-called "Hazardous Waste" (assuming that the law has not been changed since I last had involvement). The number, as I recall, is something like 5 mg/l silver. Now, there are other details, including probably a small-user exemption. At any rate, as i recall, RCRA only comes into play when you remove the "waste" from your facility. So if you can treat it within your facility, AND if your POTW (publicly owned treatment works, the sewage treatment plant) is willing to accept your effluent then RCRA doesn't come into play at all. So it doesn't formally become a so-called Hazardous Waste. As a small user in the US you can probably, more than likely, just dispose of your "silver-bearing solutions" down your municipal sewer. But... verify via local laws and regulations first.

It probably sounds like I'm just playing with semantics, but... in a number of studies I've read, photographic silver has never been shown to be especially "Hazardous." (By photographic silver I mean silver thiosulfate, as in fixer.) The general gist is that in silver thiosulfate the silver is so tightly bound that only vanishing small amounts exist in ionic form (Fwiw this is a main reason why it is difficult to electrolytically recover silver.) Earlier US EPA documents, circa 1980 say that silver thiosulfate is something like 10,000 to 30,000 times less toxic to microorganisms than silver nitrate, for example. Later studies indicate that, when photographic silver gets into a sewage waste stream, it soon ends up as silver sulfide, which is considered VERY stable.

FWIW I'm a proponent of recovering one's silver as much as can be justified. But I'm real skeptical that local "municipal waste disposal programs," where people bring in their household "Hazardous Waste" have much value related to disposing of used photographic fixer.

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Nice comments!

One other thing. Black and white much of the silver stays on the film and paper.

Any scrap photo paper should go to a waste disposal concern.

Mr Bill said:

A second significant reason that a moderately-sized commercial lab would not use a film blix is that it can't be "regenerated."

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I'm not aware of any lab-oriented, replenishable film blixes. I don't know why that's the case, but I've always assumed that part of the reason was the doubtful efficacy of film blixes as mentioned several times by @Photo Engineer. Your argument of easier silver recovery and regeneration likely is a big part of it too. However, I'm also not aware of any reasons why a film blix cannot be regenerated. It's done at a massive scale with RA4 paper blixes, after all. The same conceptual approach would not be possible with a (hypothetical) film blix?

mshchem said:

One other thing. Black and white much of the silver stays on the film and paper.

Any scrap photo paper should go to a waste disposal concern.

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Film and paper are solids. The issue discussed in the video, and my comment, is silver disposed of in the sewage system.

Mr Bill said:

That's not really ALL true, at least in the US.

The US has a law known as RCRA, which by definition can make a silver-bearing solution become a so-called "Hazardous Waste" (assuming that the law has not been changed since I last had involvement).

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Notice that I did not capitalize "hazardous waste", nor refer to any laws or statues. When I wrote those words, I was just using plain English: waste that is hazardous. The author of this video has a PhD in chemistry and his job focuses on chemical waste management. He is talking about a topic he is interested in and expressing his opinions, not giving legal advice, which of course depends on jurisdiction. The video is a deep dive into the MSDS, which I found enjoyable. I thought the bit about how blix interferes with the steel wool method of capturing silver was interesting and worth sharing.

dcy said:

Notice that I did not capitalize "hazardous waste", nor refer to any laws or statues. When I wrote those words, I was just using plain English: waste that is hazardous. The author of this video has a PhD in chemistry and his job focuses on chemical waste management. He is talking about a topic he is interested in and expressing his opinions, not giving legal advice, which of course depends on jurisdiction. The video is a deep dive into the MSDS, which I found enjoyable. I thought the bit about how blix interferes with the steel wool method of capturing silver was interesting and worth sharing.

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Blix used in RA4 printing (almost every one i've seen) doesn't really get recycled or disposed. Film goes through developer, then blix, then 2 sequential fixer baths followed by 3 stabilizer baths. There's hardly any effluent, most of the residual evaporates. There's a tiny amount of effluent that comes off the first stabilizer and the first fixer,, and a little bit from the developer. The last lab operating in Iowa City had an ancient electrolytic device that this stuff went through. C-41 minilabs are similar.
No commercial operation uses blix for developing film.

The big outfits like "The Darkroom" out in California regenerate and replenish the bleach, replenish everything else. Very amazing dip and dunk machines for film. That's the way to develop film!!!

If you want to save the environment mail your film to one of the big boys. Not for me.

koraks said:

I'm not aware of any lab-oriented, replenishable film blixes. I don't know why that's the case, but I've always assumed that part of the reason was the doubtful efficacy of film blixes as mentioned several times by @Photo Engineer. Your argument of easier silver recovery and regeneration likely is a big part of it too.

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Yes, I think that PE was most likely right about that but I don't have any first-hand experience with a film blix. So I can't say for sure. But if true then that alone would be a deal killer for a commercial lab (imo). In a larger lab, at least one that is/was in business for profit, the silver recovery and blix regeneration issues would most likely be deal killers on their own.

koraks said:

However, I'm also not aware of any reasons why a film blix cannot be regenerated. It's done at a massive scale with RA4 paper blixes, after all. The same conceptual approach would not be possible with a (hypothetical) film blix?

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Probably the major issue preventing regeneration of a hypothetical C-41 blix is the buildup of iodide which sorta "poisons" the fixer component. As I said earlier, I have no actual experience with a C-41 blix. However I once DID go through the motions of trying to regenerate C-41 FIXER. As I recall it was something like a 50 gal (US) batch of C-41 fixer overflow. I/we ran it through a commercial electrolytic recovery unit with careful monitoring while removing the majority of the silver. Followed by chem analysis for both sulfite and thiosulfate, then made the appropriate chemical additions to turn it into fix replenisher.

But... the resulting fixer had an overly long "clearing time" with C-41 film. In order to confirm that it was, indeed, due to iodide buildup, we added a similar amount of KI to some fresh fixer, then checked clearing time on that fixer. It was similarly long to the regenerated fixer, suggesting that iodide buildup was indeed the culprit.

So it on this basis that I conclude that regeneration of a film blix would also not be feasible. Because of the behavior of the fixer component.

Regarding RA-4 PAPER blix (as well as Ektaprint 2/3 prior to RA-4), yes, this is perfectly usable. We used to run something like 3,000 US gallons per day of paper (not film) blix replenisher. Which was regenerated from processor overflow. I would say there are probably two main differences between use of such paper blix vs a film blix. First, color paper is much easier to blix (bleach and fix) than film because the silver content of paper is much lower. And second, there is essentially no iodide in the color paper, so the fixing part of the blix is not "poisoned" by same.

Mr Bill said:

First, color paper is much easier to blix (bleach and fix) than film because the silver content of paper is much lower. And second, there is essentially no iodide in the color paper, so the fixing part of the blix is not "poisoned" by same.

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Yes, certainly true; this may in fact be the main reason why film blixes never made it to a production environment.

There's all sorts of technical reasons I suppose. One other thing that comes to mind is the equipment allowed for an easy adoption of bleach then fixer. I suspect it's cheaper to maintain as well.

koraks said:

Interesting, and also correct.
The bleach is a bit of an issue due to the ammonium bromide, which is apparently nasty.

Things a slightly different if you take the used chemistry away for disposal to a dedicated facility. There it depends on the nature of the disposal process if it's still beneficial to have separate bleach & fix.

It's also different for large-scale labs since desilvering and regeneration of blixes is perfectly feasible and indeed commonly practiced (for paper; no high volume film blixes are used AFAIK).

Click to expand...

This is not a legal advice, but it should be understood that the laws concerning the disposal of photochemistry are made with commercial users in mind. Driving 10 km to a recycling site will probably pollute the environment bore than 10 ;liters of iued fixer poured down the drain would. From the legal point of view, it may still be illegal in some localities to pour any amount of any chemistry down the drain.