DIY silver recovery on the cheap

[BHuij]

I know this question has been asked before, so I'll try to be specific and provide all relevant details.

My goal here is to recover small quantities of silver from my B&W film and paper fixer (TF-5) to provide to my friend who casts semiprecious metals and creates custom jewelry, so he can make me a few pieces. To that end, I'm not terribly concerned with the economics, the efficiency, the purity of the final result, or anything like that. I just think it would be cool to wear a ring made out of silver from my own darkroom, and that would only take a few grams.

In my research so far, I stumbled on this article: http://analoguephotolab.com/silver-extraction-from-exhausted-film-fixer/

Makes it seem like it might be as simple as taking my exhausted TF-5, adjusting pH to 6 with some acid or (rather alkaline) tap water as needed, and tossing in some non-stainless steel wool for a few days. Then filter the liquid through coffee filters, let them dry, burn them, and hit the ash with a torch in a crucible to get at the metallic silver left behind. Possibly with some addition of borax and/or washing soda, though I'm unclear on what exactly those do to help the process along.

1. Has anyone tried this who can confirm it works (or definitely doesn't work)?
2. Is a regular propane torch hot enough to melt the metallic silver in the ash?
3. What grade of steel wool would work best?
4. How long should I expect to need to leave the wool in the fixer before it's diminishing returns on how much silver I recover?

 

[MarkS]

That's a lot of effort to gain what will likely be a very small weight of silver.

 

[BHuij]

I... yes. I'm aware of this.

 

[Dirb9]

Did that many years ago in high school, as the photography room was adjoining the jewellery metals area, and I thought it would be a fun experiment. Finer grade steel wool allows for more surface area exposed to the fix. I used 3 or 4 balls of steel wool in a gallon of fix, left it for about a week. A propane torch worked to get most of the steel wool burnt off, but I did end up needing to finish off with an oxy-acetylene torch. Oxy-propane may get you close enough, but I don't think a plain propane torch will get hot enough. Borax (flux) helps bring impurities out together so they can be burned off or removed as slag.

In that experiment, I recovered about 10 grams of silver. My teacher pointed out that I used probably about $5 of consumables to recover a couple bucks of silver. Fixer is considered exhausted anywhere between 2-10 grams/liter, depending on whether it's being used for color or b&w, paper or film, etc.

 

[BHuij]

10g/gallon is pretty in line with what I would expect from my reading. A single 10g piece of silver would be enough to make the ring I have in mind.

I'm getting conflicting reports on what's actually happening while steel wool soaks in the fixer. Some places seem to say that the silver is attracted to the steel wool and plates it. Some say that the iron goes into solution, forcing the silver out of solution, so the silver is in the liquid you pour off, not attached to the steel wool (which would itself have a much higher melting point than silver, right?)

The guide I linked in the original post seems to indicate that you would want to pour the liquid through coffee filters to strain out the tiny pieces of metallic silver. It doesn't mention what happens to the steel wool you used.

Can anyone clarify?

 

[koraks]

I'm unclear on what exactly those do to help the process along.

They act as a flux and I think this helps the silver to melt into a neat bead.

I've only tried the first stage of the process, i.e. the ion exchange 'trick' with the steel wool (tinfoil also works). Never tried torching the residue; I should give it a spin some time. I have a jug of spent fixer that I intended to use for something like this. I should dig it up; it has silvered out quite nicely anyway.

I'm getting conflicting reports on what's actually happening while steel wool soaks in the fixer.

Essentially the iron (or aluminum) dissolves while the silver ions drop out of solution in the form of metallic silver. In layman's terms, the trick relies on silver being more noble than iron or aluminum. So the silver ends up stealing electrons from the less noble metal(s) so it can go back to being metallic silver. The silver drops out of solution in the form of tiny little particles, which appear black (as in silver negatives or prints). These particles settle on and adhere to any surface - the steel wool, the walls of the jug and (mostly) simply at the bottom of the jug as a sludge.

It doesn't mention what happens to the steel wool you used.

If everything is balanced out (i.e. you were to add precisely as much iron as needed to precipitate out all the silver) and goes to completion, you would end up with a solution containing iron ions (or iron-thiosulfate complexes, I'm not sure exactly - dissolved iron in any case) and metallic silver particles. So the iron would be dissolved/liquid and the silver will be solid. The separation is a physical one, separating the liquids from the solids. In practice, of course, you always end up with some leftover metallic iron or some leftover dissolved silver. Usually the former.

 

[beemermark]

Current films have very low amounts of silver. Back in the day when films were high in silver content it still took a commercial lab processing thousands of B&W films to make silver recovery feasible.