Two-bath fixing is still the most effective way to fix film. Combined with rotation processing it is also very efficient.
Importance of proper fixation...grim example.
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Ralph,
May I ask, just out of curiosity, how two bath fixing is more effective than single bath, assuming a film strip test is done the way I describe above?
I do two bath fixing for prints, but not for film.
Thankful for your insight.
- Thomas
May I ask, just out of curiosity, how two bath fixing is more effective than single bath, assuming a film strip test is done the way I describe above?
I do two bath fixing for prints, but not for film.
Thankful for your insight.
- Thomas
I just replenish my fixer. I have a 2 liter solution ready to go at all times. Every time I process, I remove 500ml of the working solution, and mix up 500ml fresh (or 100ml Hypam and 400ml water) to add to the 1500ml and have had no need to test, or ever run into problems. The current batch I have is well over 3 years old.
While talking about it, is there an equivalent of the clear time test for paper fixer ?
Misinterpretation of any test can be a problem. You can only slightly fault the test for that.
Experience and education can help greatly with misinterpretation.
As iodide solutions age, they release iodine. If I remember right, iodine in solution will combine with iodide to form the I3- ion (that is, the tri-iodide ion, I (sub) 3 ion with 1 negative charge).
How does free iodine, or really it's the triiodide ion, affect this test?
Thomas
The film-strip test is practical an acceptable, but nothing is as effective in removing silver and silver complexes as fresh fixer.
During the fixing process, residual silver halide is converted to silver thiosulfate without damaging the metallic silver of the image. The first fixing bath does most of the work, but it is quickly contaminated by the now soluble silver thiosulfate and its complexes. Soon the entire chain of complex chemical reactions can not be completed successfully, and the capacity limit of the first fixing bath is reached. A fresh second bath ensures that all silver halides and any remaining silver thiosulfate complexes are rendered soluble.
OK, so that is what you mean by using the word 'effective'. It is basically bullet proof and always insures total removal of the residual halide.
Do you switch the second bath to become the first bath, once the original first bath is spent, (and mix a fresh second one)? This is how I do it for prints.
- Thomas
Do you switch the second bath to become the first bath, once the original first bath is spent, (and mix a fresh second one)? This is how I do it for prints.
- Thomas
Yes there is. I have posted it elsewhere.
This same subject keeps coming up over and over so I think it is in a sticky somewhere.
PE
Well, oxidation forms Iodates and maybe even Periodates which then go on to decompose. It generally turns into a brownish mess with a strong halogen odor. It depends on concentration. Nitrogen Triiodide may even form if there are impurities and if the pH is alkaline (with ammonia), so watch for a purple color or a purple precipitate. If it looks reddish, brownish or like grapejuice do not use it. If it smells like chlorox, do not use it.
Good KI solution should be colorless and odorless. This is also a hint to emulsion makers.
Just as an aside, NaI is so unstable it is not routinely sold nor used.
PE
Interesting. I've had some bottles of KI solution that were 5 or more year old, and never have I had any of them exhibit that change. I'm not saying it doesn't happen, I've just not observed it.
If it did, I'd replace my test solution and use fresh.
No, but potassium iodide (KI) solutions are routinely sold. And the test solutions being discussed are KI solutions, not NaI solutions.
And they last in the lab for some time even as standardized solutions (with periodic restandardization to check the concentration).
My source is the Merck Index. In it, they confirm what I said above. That is one reason why the KI test is unreliable.
Where stability is required, the pH may be adjusted such that the solution is slightly alkaline and the decomposition is slowed considerably or stopped depending on pH, concentration, and storage conditions.
The addition of hydroxide ion or use in alkaline fixes is another reason why the KI test is unreliable. But you don't want to add hydroxide ion to silver salt solutions in high concentration as it can cause precipitates all by itself.
PE
Where stability is required, the pH may be adjusted such that the solution is slightly alkaline and the decomposition is slowed considerably or stopped depending on pH, concentration, and storage conditions.
The addition of hydroxide ion or use in alkaline fixes is another reason why the KI test is unreliable. But you don't want to add hydroxide ion to silver salt solutions in high concentration as it can cause precipitates all by itself.
PE
Thomas, yes. It's the exact same procedure as for prints. Same thing - just don't share your fixers between film and paper.
You can often use used paper fixers with film if you use the proper fix time, but you should not use used film fixers with paper due to the iodide content. This is a generalization that you will have to test using your workflow and materials.
PE
PE
Ron (PE), I've just come across a film fixer specifically designed for high Iodide film emulsions, it appears there was an issue with these & fixing back in the late 1920's. The fixer contained Thiocarbamide (Thiourea), I'll find it and convert the weights & volumes to Metric, the books at hand so I'll post the formulae later or more likely tomorrow.
Ian
Ian
I've never heard this about TMax or that different films exhaust fixer differently to such a noticable degree that you need to rate them...
Is this over caution or is their some grounds for this?
Ian;
I am well aware of this. For those interested in a modern example, please see the Super Fix formula of mine posted here on APUG by another member and copied from Photo.Net.
PE
If I remember your Super Fix used Thiocyanate, excellent for colour work but a potential for rather fast over fixing and image bleach with B&W papers & films, so it's nothing like the 1926 formula.
Ian
Ian
The original formula used a mix of hypo, thiocyanate and thiourea. Here is the reference.
(there was a url link here which no longer exists)
It is a matter of chemical balance and dilution.
PE
(there was a url link here which no longer exists)
It is a matter of chemical balance and dilution.
PE
Much appreciated! I've edited them back into posts #2 and #3 so they now (also) appear in their original spots.
Never hesitate to reach out so we can help edit posts that you can no longer edit yourself.
I'm afraid he died a few years ago: https://www.photrio.com/forum/threa...rey-aka-pe-photo-engineer-feb-15-2020.173245/
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- MattKing
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- Reason: redundant
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