Something's precipitating out of my Kodak Rapid Fix

Mr Bill · May 26, 2025

koraks said:
You could compare the clearing time of this salvaged fixer to fresh/good fixer using a strip of film (paper of course doesn't work as you can't really see it clear)...

Actually there is a way to sorta observe, crudely, the "clearing time" for paper. Like so: get a smallish strip of fresh photo paper, several inches long. Put several reference marks along the long side. Holding one end immerse it into some fixer to the first mark for say, 5 seconds. Then immerse to the next mark for another 5 seconds. Repeat another couple of times, then quickly immerse in water to rinse the fixer off. What you now have are sections fixed for, say, 5+5+5+5 = 20 seconds, then 5+5+5 = 15 seconds, then 10 seconds, then 5 seconds, etc.

After a good rinse put the entire strip into some developer... long enough to get fairly dark. The paper will remain white wherever the fixer completely removed the silver halide (roughly equivalent to "clearing" film). So the first completely white step gives an approximate time for complete fixing/clearing.

koraks · May 26, 2025

Yes, that's a good way, @Mr Bill! I hadn't thought of that, but it's a great way to actually test this with the paper that'll be used. It's better than to approximate it through film the way I suggested.

MattKing · May 26, 2025

Mr Bill said:
Actually there is a way to sorta observe, crudely, the "clearing time" for paper. Like so: get a smallish strip of fresh photo paper, several inches long. Put several reference marks along the long side. Holding one end immerse it into some fixer to the first mark for say, 5 seconds. Then immerse to the next mark for another 5 seconds. Repeat another couple of times, then quickly immerse in water to rinse the fixer off. What you now have are sections fixed for, say, 5+5+5+5 = 20 seconds, then 5+5+5 = 15 seconds, then 10 seconds, then 5 seconds, etc.

After a good rinse put the entire strip into some developer... long enough to get fairly dark. The paper will remain white wherever the fixer completely removed the silver halide (roughly equivalent to "clearing" film). So the first completely white step gives an approximate time for complete fixing/clearing.

This is worth its own Resource thread. In the meantime, I'll add a link to the post on my Resource regarding clearing time testing with film, found here: https://www.photrio.com/forum/resou...fixing-procedure-for-black-white-negatives.75

Doremus Scudder · May 26, 2025

Mr Bill said:
Actually there is a way to sorta observe, crudely, the "clearing time" for paper. Like so: get a smallish strip of fresh photo paper, several inches long. Put several reference marks along the long side. Holding one end immerse it into some fixer to the first mark for say, 5 seconds. Then immerse to the next mark for another 5 seconds. Repeat another couple of times, then quickly immerse in water to rinse the fixer off. What you now have are sections fixed for, say, 5+5+5+5 = 20 seconds, then 5+5+5 = 15 seconds, then 10 seconds, then 5 seconds, etc.

After a good rinse put the entire strip into some developer... long enough to get fairly dark. The paper will remain white wherever the fixer completely removed the silver halide (roughly equivalent to "clearing" film). So the first completely white step gives an approximate time for complete fixing/clearing.

I've done this before, and then used the 2x rule that applies to film. I'm curious now if that doubling is necessary or not for a safety factor. Any thoughts?

Best,

Doremus

koraks · May 26, 2025

Doremus Scudder said:
I've done this before, and then used the 2x rule that applies to film. I'm curious now if that doubling is necessary or not for a safety factor. Any thoughts?

I think the doubling is an arbitrary safety factor, but that the safety factor as such is wise to include. After all, especially when fixing paper, only the first sheet sees fresh fixer. After this, the fixer is used and it'll slow down to some extent as it's used. How big that extent is, is anyone's guess and you might conduct an additional experiment on it, but I think the pragmatic solution is just to take a safety factor and apply that.

john_s · May 26, 2025

koraks said:
I might try that, just for fun. Yield will likely be pretty horrible, but it'll be a fun experiment to see if it can be used to yield a working fixer.

And that's how sodiumselenosulfite can be made, the active ingredient of selenium toner, because selenium reacts like sulfur (same column in the periodic table). Elemental selenium is boiled in sulfite solution. Internet reports of yield vary widely. And you don't do it indoors.

RalphLambrecht · May 26, 2025

Trey said:
When Kodak stopped producing the 5gal containers of Rapid Fix part A, I guess they dumped a bunch of them into the Australian market and I've been buying them from a local supplier until they ran out recently. I seem to recall that they stopped being available in NYC in 2019 so I guess they're about 6 years old now.

But I've just noticed that at least one of the bottles has begun to separate, with a yellow precipitate forming on the bottom and some crystals floating in the solution. Presumably it's ammonium thiosulfate separating, as it now has a pretty strong sulfur smell.

I've only got one bottle left so it's not that big of a deal, but does anyone know if I might be able to get it back into solution? It still clears film so I guess it's alright for now.

it's sulfur and almost imossible to get back into solution but if you filter it through something like a coffee filter it's perfectly usable.

Trey · May 26, 2025

koraks said:
2: At the same time, what you're trying to do (I suppose) is teaching students how to do things right and you want to keep them motivated at the same time. I imagine that things like "ah, this fixer is broken so we all need to fix 50% longer" will raise some eyebrows and potentially confuse students unnecessarily. It also shows that you perhaps don't trust them with fresh chemistry or don't value them to the extent of allowing them the use of fresh chemistry. Finally, if a few prints end up underfixed and they develop brown spots in the student's hands, I suppose that won't do much for motivation either.

That's a good point and something I thought of after posting, which led me to disposing of the remainder of the open bottle. I'll maybe use the unopened 5gal bottle to get through this weekend and I do have fresh stuff on the way.

It actually is about $400.00AUD worth of fixer to replace, even though I paid way less than that.

koraks · May 27, 2025

Trey said:
It actually is about $400.00AUD worth of fixer to replace, even though I paid way less than that.

OK, that's a significant amount, but I'd focus on the actual purchase value more so than a hypothetical retail value. Anyway, now we're in accounting territory, which I've always experienced as similarly flexible to a gymnast at the height of her physical prowess.

Anyway, you might be able to salvage the other bottles that haven't gone as far downhill as this one - and the bottles that aren't affected at all (assuming some of them aren't) would of course be fine to use anyway.

john_s said:
And that's how sodiumselenosulfite can be made

I've been tempted to do that in the past, but I guess I ain't quite dumb enough to go there, LOL!

khh · May 27, 2025

Samu said:
It is elemental sulfur. If the fixer is unused, or used only for some times, sulfurization of fixer will lead to precipitation of elemental sulfur. But if this reaction happens in used fixer (or in blix in color paper process RA-4)., the product will be a black salt. silver sulfide (Ag2S), which will stain all the vessels and equipment. It is very ductile. almost like a metal, and is not soluble in water. It is actually the same compound that tarnishes silverware and jewelry. Kodak recommends using a household bleach (sodium hypochlorite solution), followed by standard photographic fixer for removing these stains

Oh, is that what that is? I've had used fixer deposit a silvery layer on the walls of clear glass bottles that made them look like mirrors.

koraks · May 27, 2025

khh said:
I've had used fixer deposit a silvery layer on the walls of clear glass bottles that made them look like mirrors.

That's actually silver and it only happens with used fixer, since that contains silver.

Something's precipitating out of my Kodak Rapid Fix

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Something's precipitating out of my Kodak Rapid Fix

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