Least expensive Silver Solvent to strip unexposed film for Silver Recovery?

Kino

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Wondering if there is a less costly alternative to buying enough sodium thiosulphate to de-silver a large amount of unexposed film for silver recovery?

Since it's not going to be used for anything other than running through a silver recovery unit, it doesn't have to be "photo pure", just liberate the silver.

Suggestions?
 

koraks

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Pool-grade thiosulfate is pretty cheap, no? Also, you only need enough to strip off the majority of the silver; you don't need archivally stable processing. So you can wear out the fixer as far as you like (it'll even help with the silver recovery).

I suspect cheaper methods of getting the silver off the film would involve essentially breaking down the gelatin emulsion. E.g. dissolve the gelatin in a high-pH environment - just let it soak for a day or so in sodium hydroxide. However, it'll be challenging to break it down well enough so that the silver halide actually liberates; you'd still be left with a mass of organic contamination that will likely f* up your silver recovery.

If you're talking seriously big amounts of film, surely the revenues from the silver recovered would offset the relatively limited investment in sodium thiosulfate. Am I missing anything?
 
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Kino

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Not missing anything; just wondered if there were any old silver recovery hands out there who had some tricks. My experience is limited to running commercial grade extraction units; not doing it piecemeal in my basement...

Don_ih said:
If the film is actually unexposed, you'd make more money selling it than recovering the silver. People will buy any old film.
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Not this junk. I'd spend more time answering outraged emails and refunding money than it would be worth.

Fungus and B+F of .50 anyone?
 

Ian Grant

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I worked in the precious metal industry for nearly 20 years, we recycled Fixer from X-ray machines adding Ferric Chloride as a Silver bleach, and then plated the Silver from the solution, which was then re-used.

Ian
 

koraks

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Dustin McAmera said:
instead of 'let it soak for a day' Abney says boil it in saturated caustic soda for a quarter-hour
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Makes good sense; that'll speed things up pretty dramatically!

I routinely soak hardened gelatin in dilute lye (recycling carbon transfer temporary supports), but I just let it sit overnight. The gelatin tends to retain much of its integrity that way, which is what made me doubt the effectiveness of this approach. However, boiling should in a concentrated solution break things up pretty well. It'll smell...soapy, I imagine.
 
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Kino

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Ian Grant said:
I worked in the precious metal industry for nearly 20 years, we recycled Fixer from X-ray machines adding Ferric Chloride as a Silver bleach, and then plated the Silver from the solution, which was then re-used.

Ian
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Does this work with both exposed and unexposed film?


That's an interesting approach! Thank you for the reference!
 

grain elevator

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Can you get used fixer in sufficient quantity, from a lab? It would probably be good enough and you wouldn't need to waste fresh fixer.
 
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Kino

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grain elevator said:
Can you get used fixer in sufficient quantity, from a lab? It would probably be good enough and you wouldn't need to waste fresh fixer.
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I would think most labs that use a large amount of fixer would desilver and reconstitute it for their own use.

Pool-grade Thiosulfate is probably the cheapest route yet, but with unexposed stock.
 

eli griggs

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I simply use fixer from regular processing, film and papers, never to exhaustion and pour it into a large plastic jug with paper or film for a long period, adding more fixer and film, papers, looking for clear film base polymer.

I only add paper in small amounts and saved my rejected pics untill I have fixer sufficient for full sheets to be processed in pairs, back to back.

I need a new stainless pail and top, or a stainless turkey fryer and lid that can be clamped down to allow papers to be reduced to charcoal, at a low temperature, soot to cook off silver, like the military mobil darkrooms have used.
 
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mshchem

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If you had 1,000 lbs of film you'd be lucky to recover 10 ounces. Then before you could sell it you'd have to refine it, assay it.....

Not worth the effort.
 

GLS

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Handling boiling 25 molar sodium hydroxide is not advisable! Get a drop of that on your skin and you're talking immediate, horrific burns. In the eyes? Guaranteed blindness.
 

eli griggs

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mshchem said:
If you had 1,000 lbs of film you'd be lucky to recover 10 ounces. Then before you could sell it you'd have to refine it, assay it.....

Not worth the effort.
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Where did you come up with that ratio?

Your figure seems wildly off others I've seen in the past.
 

mshchem

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eli griggs said:
Where did you come up with that ratio?

Your figure seems wildly off others I've seen in the past.
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Just to spitball a figure. Imagine that fresh film is 1/10 of 1% AgX by weight.

That yields 10 lbs of silver halide, figure of that it's 60% silver. So 6 lbs of silver.

How much does a 5 foot strip of 35mm film weight? 20 grams??? For spitball purposes let's use 28.35g 1 oz avoidupois. 16 36 exposure rolls per pound

16,000 rolls of film = 1000 lbs of film = 6 pounds of silver.

454 x 6 ÷ 31.1 = 87.6 Troy ounces of pure silver, @ 31 USD per ounce that's $2700 US.

Now remember that you still haven't done anything to extract, refine and find a buyer.

Most of the time silver is recovered because it's illegal to dump it down the drain. Used to be a market for X-ray films, custom was to extract the silver with sodium cyanide solution.

You also will have 990 lbs of stripped film you will need to get rid of (sneak it into the trash at work)

Now say I'm off by a factor of 10, and there's $27,000 / 1000 lbs of film.

Unless you have 100,000 pounds annually it wouldn't be worth the effort.

Kodak recovered silver from their processing facilities because it was initially the right thing to do, then to comply with regulations.

Try to melt an ounce of silver sometime (a prerequisite for pouring your nice ingots).
I wonder what Adox does with their sprocket holes?
 

MattKing

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A long time former member here used to distribute a product that was scaled appropriately for the smaller volume user who wished to reclaim silver from the spent fixer resulting from their darkroom use.
When he started, the silver extracted was valuable enough that after the silver refiners took their cut, the users would usually get a cheque back for a small but useful amount.
By the time he left here, he was telling people that in most cases the refining costs exceeded or were just slightly less than the value of the silver - that the value in doing so was basically its positive effect on the environment.
The market price of the silver remained reasonably high through that time - it was the refining costs that made the difference.
The former member hasn't been here for a while. I hope he is well.
 

koraks

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mshchem said:
Imagine that fresh film is 1/10 of 1% AgX by weight.
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Silver content of BW film in g/cm2

I've been searching the web for some data on silver content of film to see whether these price rises in film are really justified by the increase in the silver price. Please can someone contribute a figure for the mass of silver bromide in film in g/cm2. I have been using a figure of...
www.photrio.com
Let's go with 5g/m2.

Acetate is something like 1.5g/cm3; let's use that as an average film weight. 1000lbs = ca. 450kg so that makes roughly 0.3m3 of film.
Let's assume a film thickness of 120um (=0.00012m), which seems to be pretty common for 35mm. That would make our 0.3m3 of film correspond to an area of ca. 2500m2.

2500m2 @ 5 g/m2 = 12.5kg of silver. Should be doable to recover 10kg or so from it (20lbs or so).

Let me know if my math is off an order of magnitude somewhere; I do that sometimes to check if you're all paying attention...
 

mshchem

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I really don't know. But I know I fellow who ran a shop with film and print Fuji machines they were maxed out for 30 years. He ran all the blix and fixer through a fancy industrial electrolytic recovery unit. He had buckets of almost pure silver sludge. I think he told me3he sold it and got a check from the refinery for 7-8,000 USD. I think silver was in the 20 usd/oz range.

Easy way to try take a sample of your spent fixer and have it analyzed
 

MattKing

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And be sure to enquire about how much the refiners are charging to handle what byproduct you have. My understanding is that those costs are now much higher.
In the case of this thread though, @Kino is looking for a solution that will create the byproduct in the first place - he isn't using fixer for other purposes. So he will need to factor in the cost of that as well.
I seem to recall, but could very well be mistaken, that there are agricultural sources for bulk sodium thiosulfate. If so, that also might be a solution.
And finally, I'm surprised that there aren't people in @Kino 's old line of work - handling gobs of motion picture film - that would have this type of information.
 

Don_ih

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I still say sell it.
I'd be using it, probably (depends what it is).

Also, bulk film will often age badly on the outside of the spool but is much faster, with less fog, a few windings in.
 

mshchem

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Yeah, sodium thiosulfate is available in 25kg bags, one use that I'm aware of is for removing excessive chlorine from pool water.

EK used to sell a very simple device that contained iron wool, when the blix and fixer effluent drizzled through the cartridge the iron would replace the silver and you would end up with a black sludge that was rich in silver.
 

mshchem

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Don_ih said:
I still say sell it.
I'd be using it, probably (depends what it is).

Also, bulk film will often age badly on the outside of the spool but is much faster, with less fog, a few windings in.
Click to expand...

Absolutely, there's always some nut who wants weird film.
 

mshchem

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I hang out some at my friend's coin shop. He buys old sterling (0.925) silver flatware tea sets, etc. He just smashes them flat removes anything (plaster, stainless blades on knives) packs them usually 40 lbs in a sturdy cardboard box. I think he gets about 90% of the silver value. My buddy pays 80% of melt.

Gold scrap is better He pays 90% and gets close to 99%. He needs a couple pounds of scrap gold as they melt it all together and use X-ray emission spectroscopy to check on gold, silver, copper content etc. He gets paid for the gold.
 
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Kino

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MattKing said:
And finally, I'm surprised that there aren't people in @Kino 's old line of work - handling gobs of motion picture film - that would have this type of information.
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They are pretty much all gone; left in the late 1990's when film print production crashed. Now there are only a few dedicated Silver Recovery companies and they won't talk to you without a multi-year contract with a lease of their machines and a cut of the harvested silver.

Film-based infrastructure for motion pictures is all but gone. Of what is left, 99% is for process and scan deliverables; prints are increasingly hard to obtain at any cost if you are not Chris Nolan.
 
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