Silver quantity testing

[nbagno]

Does this look like a testing strip to determine the silver content of used fixer?

 

[koraks]

Item title suggests it, but product description is lacking. I'd ask the seller. While you're at it, also inquire if they include instructions in any other language than Chinese...might be tricky to interpret the outcome if all you have are Chinese instructions.

 

[Lachlan Young]

Does this look like a testing strip to determine the silver content of used fixer?

This is what they seem to be, rather than the equivalent of this product, which is what you want for checking the actual approx amount of silver in the fix. In other words, the ones you linked to are qualitative (ie they'll give a yes/ no result for silver over a specific amount) rather than quantitative or semi-quantitative.

 

[Nicholas Lindan]

Does this look like a testing strip to determine the silver content of used fixer?

Er, no. At 20mg / liter these things will turn color with your first print - after all, at that point there is indeed silver in the fix.

Most folks use https://www.digitaltruth.com/data/formula.php?FormulaID=57

 

[nbagno]

I have an X-rite recovery unit, which was new in the box but without the silver test strips. I would like to know how much silver is estimated to be in the exhausted fixer. The first time I ran the unit filled with the exhausted fixer, it didn't recover anything. I'm looking for the proper test strips to test the amount and stumbled on this eBay listing.

 

[nbagno]

This should work. https://www.ctlscientific.com/cgi/display.cgi?item_num=90741&title=Ag-FIX-Test-Sticks

 

[Lachlan Young]

This should work. https://www.ctlscientific.com/cgi/display.cgi?item_num=90741&title=Ag-FIX-Test-Sticks

Yes - those are what you want. For what it's worth, even exhausted fix will probably only give you a couple of grammes a litre of silver.

 

[nbagno]

Yes - those are what you want. For what it's worth, even exhausted fix will probably only give you a couple of grammes a litre of silver.

I just expected the machine to register that there was something... Once the x-rite machine had enough fix to fill the tank, I turned it on and according to the LED's on the unit there was not enough silver to even register. I just want to know how much is in there before I run the next batch through the machine.

 

[Rudeofus]

@nbagno : Silver level is only one factor in determining fixer exhaustion. You can dissolve much, much more Silver Chloride than Silver Bromide or Silver Iodide in a given quantity of fixer. The difference is also not the same for Sodium Thiosulfate vs. Ammonium Thiosulfate fixers. Therefore there is not one number to tell you "fixer is exhausted". Typical silver levels in exhausted rapid fixer are one to a few grams of silver per liter. Most amateurs probably won't reach such a high level unless they have unusually high throughput.

 

[beemermark]

I have an X-rite recovery unit, which was new in the box but without the silver test strips. I would like to know how much silver is estimated to be in the exhausted fixer. The first time I ran the unit filled with the exhausted fixer, it didn't recover anything. I'm looking for the proper test strips to test the amount and stumbled on this eBay listing.

There's nothing in the unit because you need to run thousands of rolls of B&W through it to even get 1 or 2 ounces of silver. And that's back 30 years ago when films had a high level of silver content, which they no longer have. Professional labs back in the day that might run a thousand rolls a day used the recovery units. Amateurs never did.

 

[nbagno]

There's nothing in the unit because you need to run thousands of rolls of B&W through it to even get 1 or 2 ounces of silver. And that's back 30 years ago when films had a high level of silver content, which they no longer have. Professional labs back in the day that might run a thousand rolls a day used the recovery units. Amateurs never did.

I would say that there is not enough silver in the fix to even register on the machine. It's made to recover silver from x-ray negatives so...

 

[Mr Bill]

Does this look like a testing strip to determine the silver content of used fixer?

Yeah, it looks like a conventional silver estimating paper. If you look it up in Google there's a photo that shows the back of the package, with a comparison chart. It ought to work fine for your purposes.

Er, no. At 20mg / liter these things will turn color with your first print

It's been some years now, but I've spent enough time working with cut-rate ways to measure silver concentrations in fixer that i would be astounded if a silver test paper could detect 20 mg/liter of silver in fixer. Now, with special techniques you could reliably "see" down to 100 mg/l, but below that, no, I don't think so. In the normal usage of these test papers I don't know that you could reliably see lower than maybe 500 mg/l (1/2 gram per liter). But my memory is pretty fuzzy on this.
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Once the x-rite machine had enough fix to fill the tank, I turned it on and according to the LED's on the unit there was not enough silver to even register

Did you have some expectation as to the silver concentrations? I mean, for example, did you keep track of the film through it? If so it ought to be possible to make a rough estimate of the silver content, within perhaps a factor of 2 or so.

I don't know how your X-rite machine measures silver, but back in the day we, at the outfit where I worked, looked at a handful of "measuring" systems. We were never very happy with them so always ended up running our systems manually, by which I mean specifically setting the amperage and run times, etc. But you need a fairly good estimate of how much silver is there in order to do that.

Fwiw electrolytic systems typically cannot take silver concentrations down to really low levels. The best you can do, near the end, is to reduce the plating current and watch for the plate to begin to darken. At this point you might be down around 1 or 2 tenths of a gram per liter (100 or 200 mg/L), which you're not gonna be able to measure with silver-estimating paper (at least not conventionally). So in essence you are sort of using the electrolytic unit itself to evaluate how much silver is left (when you are running out of "recoverable" silver the electrical current will begin to cause "sulfiding" of the fixer, which darkens the plate). What you might conclude from this is that if have, say a half gram per liter, or more, then you should be able to get SOMETHING out of it, electrolytically. Assuming that the X-rite sensor lets you do so.

 

[Mr Bill]

I would say that there is not enough silver in the fix to even register on the machine. It's made to recover silver from x-ray negatives so...

You'd have to be giving your fixer pretty light usage for it to be completely below the capabilities of an electrolytic recovery unit (they don't care if it's from x-ray film or not). But only you know how you're handling it.

Beemermark makes a good point, although greatly exaggerated, that there is not as much silver in film as many people think. So one needs to process a pretty significant amount of film to justify buying a recovery unit. But... since you already own one, the main issue is how to best use it.

In general the best way to use an electrolytic silver recovery unit is to use fixer with at least a moderately high silver concentration. Why? Consider this situation: say that your unit has a lower end recoverable limit of 1/4 gram per liter of silver. Then, say that you only use your fixer up to a level of 1/2 gram per liter. This means that you'd only be able to recover about half the silver, right? You start out with 1/2 g/l, desilver down to 1/4 g/l, so you only get half, more or less.

On the other hand, say that you use your fixer up to about 2 g/l silver. If you desilver this down to the same 1/2 g/l level, you have now recovered about 1 1/2 g/l out of the 2 g/l available. So you are now recovering 3/4 of the silver. And so on.

Here's the problem with building up a higher silver concentration. For best longevity of your film, etc., you want the fixer to have a lower concentration of silver. So the two goals are contrary to each other. There is a solution to this, which is about as close to the proverbial free-lunch as you're likely to get. It's to use multi-stage fixing. For example, consider a 2-bath fixer. You first put your film in fix-1, which does the vast majority of the fixing. Then film goes into fix-2, which finishes off the job. The result is that fix-1 builds up a higher concentration, which is good for silver recovery. And fix-2 runs at a lower concentrations, which is good for the film's longevity. So by doing this sort of thing you are able to control the silver concentration reaching your recovery unit.

So the bottom line is that you are in a position to control what gets to the silver recovery unit, BUT you have to sort of understand how things work. And it has to be worth the effort. For example, a three-stage fixer is even better than two, with respect to recovering silver. But if the extra recovery is only a tiny amount of money it might not be worth your effort. So you have to weigh the situation to make a decision. But it sorta starts with knowing how much silver is there to begin with. Or, to have someone who does know these things to give you real explicit instructions, which is sorta what the Kodak Z manuals do for C-41 processing and the like.

 

[Lachlan Young]

And that's back 30 years ago when films had a high level of silver content, which they no longer have.

By any measure this is inaccurate. Silver coated/ m2 has changed much less than the marketing claims of some self-interested resellers wanted you to believe - but the use of the available silver got much better. On the other hand, the silver levels in litho film and X-ray materials are significantly higher - litho film in particular, in order to deliver the very high contrast the process demands. And the quantities of these materials that goes through any given system is going to be much higher indeed. Consider that for one finished B1 sheet, printed in offset on both sides in full colour (which is what you'd need to deliver a fairly average A4-ish 16pp signature), you'd use approx 8750-9000 sq in of film, purely to expose the plates. That's equivalent to well over 100 rolls of 120/135.

 

[nbagno]

Thanks for all the responses.