How much silver is actually in modern films and papers?

[foc]

This is a question about silver in the wash water.

When I operated my minilab (in Ireland), I had a Metafix silver recovery unit, and all the lab's effluent, including wash water, was put through the unit. This was a requirement of our local Environmental Protection Agency.

 

[TomR55]

Good grief... this reminds me of an old battle axe photo teacher in my district (thankfully retired!), who switched entirely over to digital, then went to the district to try to get us other heathens to also switch over to digital, for the very same reason. Us heathens won.

As an aside…, I am certain that someone, somewhere has done studies on the environmental costs associated with the digital footprint. Assuming a greater number of producers/consumers on the digital side of the street, I don’t believe that the trace amounts of silver present in wash water poses a significant problem?

 

[koraks]

As an aside…, I am certain that someone, somewhere has done studies on the “environmental costs” associated with the “digital footprint.” Assuming a greater number of producers/consumers on the digital side of the street, I don’t believe that the trace amounts of silver present in wash water poses a significant problem?

LCA's are fickle subject matter. And even so, in a confrontation with an environmental agency that's enforcing effluent regulations, it's not going to help to offer this argument.

 

[TomR55]

LCA's are fickle subject matter. And even so, in a confrontation with an environmental agency that's enforcing effluent regulations, it's not going to help to offer this argument.

I’m certain you’re correct on that score. I was thinking more about the photo teacher who switched to a digital workflow to mitigate environmental damage due to silver.

 

[koraks]

Yes, of course; you're right there. That is to say - there'll be lots of arguments for and against both sides, but no conclusion. The LCA for whatever imaging technology you choose will never be sufficiently representative to make "the right" decision. There's always a limit to how deep you can dive into the ecosystem and supply chain, too many unreliable assumptions that end up having too much influence, etc. Moreover, the 'environmental impact' argument when followed through always ends at the conclusion that it's best to walk deep into the woods, lie down there and don't get up. Or perhaps less dramatically: the lowest environmental impact (or any other impact, really) has the photo that wasn't made to begin with. The problem is that we have to strike a balance between doing what we need/want/like to do, and not being too harmful in doing so. So I personally think a better approach is to choose a mode (whether it's digital or film) and then trying to be as sensible as realistically achievable in pursuing that option.

 

[relistan]

Wash water will certainly have a tiny amount of silver from the fixer that was left on surfaces and absorbed into the film. But it's got to be absolutely miniscule. Agree with all the above comments to have your own testing done on the effluent.

 

[Harman Tech Service]

Hi old_squint,
If you like, I can send you a couple of fixer test strips to use on your wash water.

Semi-quantitative test strips Ag-Fix for silver in fixing baths

The convenient Ag-Fix test strips allow a simultaneous semi-quantitative determination of silver and the pH value in photographic solutions.

www.mn-net.com

I suspect the results on these will be zero.
Just send your address to:
technical@harmantechnology.com
You could also measure the average silver content of your fixer and estimate the carry over into the wash and then apply a (huge) factor for dilution.
Regards,
David

 

[MattKing]

Thanks for chiming in @Harman Tech Service /David!

 

[Doremus Scudder]

Interesting that we haven't heard back from the OP yet...

 

[Mr Bill]

If you like, I can send you a couple of fixer test strips to use on your wash water.

Semi-quantitative test strips Ag-Fix for silver in fixing baths

The convenient Ag-Fix test strips allow a simultaneous semi-quantitative determination of silver and the pH value in photographic solutions.

www.mn-net.com

I suspect the results on these will be zero.

Thanks also for chiming in, David. But with those strips having a lower test limit of 0.5 g/l I would concur that they likely won't show anything.

FWIW long time back, circa 1980?, Kodak published (I think it was public, but not well-known) a brief document on improving the sensitivity of their silver test paper. Essentially, instead of a quick dip of the test paper they used a 30-second immersion, motionless, in a small cup or beaker, then rinse and dry the test paper. Then read the density with a densitometer (I'm thinking it was a red-filter density, to mostly exclude the yellow base color of the test paper). Finally compare it against a calibration chart MADE BY THE USER with their own fixer or blix and test paper. Unfortunately, for hobbyists, this calibration chart requires sending a half-dozen or so samples to an analytical lab, so perhaps a cost of maybe $100 to $200 US. This AND the ability to produce multiple samples with silver concentration in the desired range.

At the outfit where I worked, a large photo lab, we could pull periodic samples from electrolytic silver recovery machines to get such samples. The results were surprisingly good - with fixer it could detect to under 1/10 g/l silver, and could reliably tell the difference between, say, 1/10 and 2/10 g/l silver. (There is no "standard" test paper that can come near this.) One other downside to the extended-time dip test - it could only measure up to a max of about 2 g/l silver... the test paper essentially became saturated. Around that time we added an AA unit to our on-site chem lab specifically to do silver analysis, but continued using the extended-time dip test for quick screening.

But I would guess that the OP's situation is with silver levels far lower than this. As a point of reference, in the US the law known as RCRA establishes what constitutes a "Hazardous Waste," requiring the use of licensed Hazardous Waste haulers, etc. As I recall the lower limit for photographic silver was something like 5 mg/l silver - this is roughly 10 to 20 times lower than our extended-time test paper method could determine. (1/10 gram per liter is 100 milligrams per liter unless I lost a zero somewhere.) Higher than 5 mg/l would become a Hazardous Waste IF certain other criteria are met. Anyone who wants to know for sure should read the actual law - US RCRA. I THINK there may be minimum weight exclusions, and the silver must be "leachable, "or something to that effect. So discarded film or silver jewelry, etc., would not be a Hazardous Waste, but photographic fixer or wash water, above 5 mg/l silver would possibly be so. I'm going strictly from a sorta vague recollection of the law from maybe 15 years ago, so if anyone wants to sure of the specifics THEY SHOULD READ THE LAW. (FWIW I think that maybe an exemption had been made for materials being sent out for reclamation as opposed to disposal, but again, read the law for accurate info.

Sorry for running so far off topic but some of these things may be pertinent to some forum members.

 

[Mr Bill]

Interesting that we haven't heard back from the OP yet...

If I was the OP I wouldn't put much out here on a public forum.

 

[Mr Bill]

I've not heard of people trying to recover silver from wash water. Fixer and blix absolutely.

You probably just didn't run with the right crowd to hear about it. This was absolutely a big deal, in the US at least. Somewhere around the early 1980s the strict effluent regulations were being applied and it became necessary for photofinishers to deal with them.

It was the individual municipalities that set their own limits - some were very strict on silver, and some were "lenient," using the same 5 mg/l as set for Hazardous Waste determination. With this rather high limit it was fairly easy for a smallish lab (mini-lab for example) to meet the limit. Certain steel wool style cartridges, under the right operating conditions, could sorta reliably hold silver concentrations below 2 or 3 mg/l silver. So it was possible to mix the wash water with fixer (previously desilvered electrolytically to under about 1/2 to 1 g/l) together and run through a high-performing steel wool cartridge to meet the looser silver limits.

If one needed to meet tighter silver limits, say below 1 mg/l silver, there was essentially no simple technology for this. So this was one of the primary reasons (or so I was told) for development of the so-called "washless systems." No sewering permit was necessary because there was no sewer connection for the mini-lab machines - ALL of the waste had to be hauled off for treatment. This was somewhat feasible because the "washless" treatment ran at very low replenishment rates relative to a conventional wash.

Labs that were large enough to afford more sophisticated technology (and people able to deal with it) could work with conventional wash water. Circa 1980 my boss oversaw the purchase and installation of an ion-exchange in our main lab. (I and the QC staff had to oversee the operation, with the Material Conversion Dept doing most of the physical work.) This was an extra-large system custom-built by an outfit called CPAC, which was the premier maker of such, and related things. Ours could pump 50 gallons/per minute of overflow wash water through the resin columns, which could nearly keep up with our maximum throughput for RA-4 paper processing. (To put it in perspective we were printing and processing about a dozen master rolls of color paper every day; master rolls come one per pallet.) As I recall the wash water was running about 2 or 3 mg/l silver, and fresh resin could lower this to about 1 or 2 TENTHS of a milligram/liter of silver - this was low enough to meet our effluent-control limit of something like 0.2 or 0.3 mg/l silver. But... there were a lot of issues, of which I will spare the reader...

But... I should note that "normal" labs will have substantially higher silver concentrations in their wash water. Maybe 5 or 10 times higher, as a wild guess. We ran multi stage blix tanks followed by a multi-stage low-flow prewash (part of a Kodak process alternative), all with counter-current flow replenishment, and squeegees everywhere, intended to keep the silver more concentrated where we could handle it, and to keep silver out of the wash water.

We ultimately changed to a different sort of system, relying mainly on multiple multi-stage systems with finely-tuned flow rates such that more conventional silver recovery methods could keep us comfortably under the 0.2 mg/l silver limit. (Fwiw these were all with custom configured processing machines... no normal system could achieve such results.)

 

[alanrockwood]

At the large lab outfit where I worked our permit limited silver concentration to 0.2 g/L, which would be virtually impossible for the normal person. (This is roughly 0.2 parts per million....

I think you may have a typo in your post. Do you mean 0.2 mg/L not 0.2 g/L?

0.2 g/L is 0.2 parts per thousand, not 0.2 parts per million.

 

[Mr Bill]

I think you may have a typo in your post. Do you mean 0.2 mg/L not 0.2 g/L?

0.2 g/L is 0.2 parts per thousand, not 0.2 parts per million.

Holy cow! I can't hardly believe that someone is actually reading my posts carefully enough to catch that. You're absolutely right... the correct number is 0.2 mg/L or 0.2 parts per million. (Way too late to edit it now.)

 

[MattKing]

Holy cow! I can't hardly believe that someone is actually reading my posts carefully enough to catch that. You're absolutely right... the correct number is 0.2 mg/L or 0.2 parts per million. (Way too late to edit it now.)

But not too late for everyone here .
Fixed for you.

 

[Mr Bill]

But not too late for everyone here .
Fixed for you.

Thanks Matt! Sorry that you have to read through enough to find it (wink ; I have a a hard time bringing myself to use emojis)

 

[MattKing]

wink ; I have a a hard time bringing myself to use emojis

Could that be related to having come from a DOS based, text-centric computing background?

 

[Mr Bill]

Could that be related to having come from a DOS based, text-centric computing background?

Good likelihood. Even a bit before MS-DOS which I even know was written by Tim Patterson of Seattle Computer Works and bought by a couple young guys who didn't reveal who the real customer was gonna be.

 

[MattKing]

WordPerfect 4.1 is where I started actually using computers.
Green text on a dark screen - it didn't seem necessary at the time to want more.

 

[Mr Bill]

WordPerfect 4.1 is where I started actually using computers.
Green text on a dark screen - it didn't seem necessary at the time to want more.

Ha ha, yep. We used to have that on the relatively few personal computers in the office. I remember that when it opened it actually held TWO documents that could be toggled back and forth. But most people only knew about the one they were using.

I used to occasionally prank people who knew something about these computers, including the uptight guy who was in charge of the lab computers (primarily a PDP-something mini-computer) and was deathly afraid of making a mistake. What I did was... when they left the computer, with their document on-screen - I flip to the second document, go to the middle part of the screen, and type... "OK, now formatting Drive C: ..." Then flip back to their document.

They finish their document, then attempt to to Quit the program, which normally returns to the DOS prompt. But... since there is now a second document existing THAT document comes on-screen, and to their horror it looks like a DOS prompt that says "OK... now formatting Drive C: ..." (you have to be standing by in case they don't catch what's going on)

We should probably let this thread get back on topic, though.
Ps, feel free to delete the idle chatter; it's just fun to reminisce a bit.

 

[Maris]

Years ago I worked as a scientist for the state with a special interest in toxins and their biological effects. The anxiety about photographic silver in the environment is perplexing to me.

Used fixer does not contain silver metal as such but rather a non-stoichiometric mixture of silver thionates. Thionates are oxidation products of thiosulfate and they all have very similar properties.
The main thionate in used fixer is silver tetrathionate, Ag2.S4.O6, and I reckon it is rather unremarkable. It's not particularly toxic. It does not pose a noticeable Chemical Oxygen Demand on the environment.
I can't find an instance of a Biological Oxygen Demand problem. Similarly I can't find a instance where it poses a bio-accumulation hazard.

Silver tetrathionate is mildly reactive and there are two main reaction pathways.
It can react with metals that are less noble than silver by plating out as silver metal. It is a pretty experiment to throw a copper coin into used fixer and see that the coin becomes silver plated.
The other reaction is with the sulfide ion which is ubiquitous in waste water streams. The result is silver sulfide which is geologically stable and does not practically participate in chemical or biological reactions.
Sepia photographs include silver sulfide which give them their long term stability. Silver miners hated sulfide ore because of the effort of refining the metal from it.

Another thing curious to me is the fear of silver metal as a hazardous biocide.
Would you believe that there are people who actually consume silver metal in the form of a colloidal suspension? This in pursuit of supposed health benefits. Colloidal silver comes in concentrations
from 10 to 30 parts per million and a typical dose is 15 ml per day. If this dose is maintained these people have skin that turns blue! The silver metal also accumulates in other body tissues and ultimately the argyria
becomes permanently disfiguring but not life threatening. Regular drinkers of colloidal silver excrete silver every day at concentrations higher than the trace amounts in photographic wash water and they do it legally
and without restriction. Oh, the irony.

The amount of silver in photographic materials varies but for back of the envelope calculations I used to allow 1gram per square metre.

I guess none of the above, interesting (to me) as it is, helps the OP whose problems are regulatory rather than chemical.

 

[Alan Edward Klein]

Years ago I worked as a scientist for the state with a special interest in toxins and their biological effects. The anxiety about photographic silver in the environment is perplexing to me.

Used fixer does not contain silver metal as such but rather a non-stoichiometric mixture of silver thionates. Thionates are oxidation products of thiosulfate and they all have very similar properties.
The main thionate in used fixer is silver tetrathionate, Ag2.S4.O6, and I reckon it is rather unremarkable. It's not particularly toxic. It does not pose a noticeable Chemical Oxygen Demand on the environment.
I can't find an instance of a Biological Oxygen Demand problem. Similarly I can't find a instance where it poses a bio-accumulation hazard.

Silver tetrathionate is mildly reactive and there are two main reaction pathways.
It can react with metals that are less noble than silver by plating out as silver metal. It is a pretty experiment to throw a copper coin into used fixer and see that the coin becomes silver plated.
The other reaction is with the sulfide ion which is ubiquitous in waste water streams. The result is silver sulfide which is geologically stable and does not practically participate in chemical or biological reactions.
Sepia photographs include silver sulfide which give them their long term stability. Silver miners hated sulfide ore because of the effort of refining the metal from it.

Another thing curious to me is the fear of silver metal as a hazardous biocide.
Would you believe that there are people who actually consume silver metal in the form of a colloidal suspension? This in pursuit of supposed health benefits. Colloidal silver comes in concentrations
from 10 to 30 parts per million and a typical dose is 15 ml per day. If this dose is maintained these people have skin that turns blue! The silver metal also accumulates in other body tissues and ultimately the argyria
becomes permanently disfiguring but not life threatening. Regular drinkers of colloidal silver excrete silver every day at concentrations higher than the trace amounts in photographic wash water and they do it legally
and without restriction. Oh, the irony.

The amount of silver in photographic materials varies but for back of the envelope calculations I used to allow 1gram per square metre.

I guess none of the above, interesting (to me) as it is, helps the OP whose problems are regulatory rather than chemical.

Allowing 28 grams to an ounce at $3.40 per, that's about $.12 worth of silver per square meter. There's probably more silver in a old dime.