Fixing Overnight

Doremus Scudder · Mar 24, 2018

bvy said:
That's more or less how I would I have described the test. My problem with it is that it assumes the fixer being tested is capable of fully clearing the film. If it's exhausted, then that first drop you put on the film will not fully clear the film, and the test tells you how long the fixer is capable of doing the most it can do. Rereading what you have, I don't think we disagree. You do call it a "test for clearing time" which is accurate. I think some people mistakenly think of it as a test for fixer efficacy.

bvy,

You're inventing a problem that doesn't exist.

The clip-test assumes you have established a base line (clearing time) using fresh (i.e., known-to-be-good-and-work) fixer that is mixed in one of the recommended dilutions for your application. Otherwise, it's just a shot in the dark.

Fresh fixer is a) freshly-mixed from dry chemicals that are known to be fresh or b) freshly-mixed from liquid concentrate that is known to be fresh.

A drop of fixer is placed on the film and left to do its work for 30-60 seconds. Then the entire strip of film is immersed in the fixer and agitated; simultaneously, you start timing. All this under good lighting so you can see what's going on. When the film is clear enough that you can no longer see the area under the drop as separate from the rest of the film, you have "cleared" the film and you should note the time (this is your "clearing time"). Be aware that it is the time it takes to clear the film that is important here. Exhausted fixer or fixer that has gone bad from age will still clear the film; just in a longer time.

When (or if) your fixer is exhausted (even partially), it will not (no way, no how) clear the film in the same time.

Now, how you want to apply your clearing time can be different. I like to fix my film for at least 3x the clearing time, especially if it is tabular-grain film (T-Max) since there are iodides in the film that take longer to fix than "conventional" films. Ilford and others say 2x. You can do the research and decide for yourself. In any case, I do a clip test with my partially-exhausted fixer before each batch and arrive at my minimum fixing time for that particular batch based on the (longer) clearing time in the used fixer.

In any case, when the clearing time for used (or unused old) fixer reaches 2x that in fresh fixer (your benchmark, remember?), the fixer should be discarded. It has been used too much or stored too long. Mix new fix. That's all there is to it.

If you have fixer that you suspect of not being able to fully clear the film, then you need to compare it to your benchmark clearing time. (If you haven't established that, then you should...)

If you fix film using these guidelines and add a bit of time for a safety factor (fixing slightly longer does no damage to film), you can be sure that your film is as fixed as it is likely to get after you have finished. The base will not be completely transparent; there is base fog and emulsion there. There may also be dyes that have not washed out completely. Modern films have stubborn sensitizing dyes in them that leave pink or blue casts to the base. This latter, however, has nothing to do with fixing; a slight color cast to the film will not affect printability or longevity.

Note that the above is for film. For prints a clip-test is less applicable, especially if two-bath fixing is used. Testing your workflow for residual silver (e.g., using the Kodak ST-1 test) is the best way. Using manufacturers' guides for throughput is the second best.

Best,

Doremus

bvy · Mar 24, 2018

Doremus Scudder said:
bvy,

You're inventing a problem that doesn't exist.

The clip-test assumes you have established a base line (clearing time) using fresh (i.e., known-to-be-good-and-work) fixer that is mixed in one of the recommended dilutions for your application. Otherwise, it's just a shot in the dark.

Fresh fixer is a) freshly-mixed from dry chemicals that are known to be fresh or b) freshly-mixed from liquid concentrate that is known to be fresh.

A drop of fixer is placed on the film and left to do its work for 30-60 seconds. Then the entire strip of film is immersed in the fixer and agitated; simultaneously, you start timing. All this under good lighting so you can see what's going on. When the film is clear enough that you can no longer see the area under the drop as separate from the rest of the film, you have "cleared" the film and you should note the time (this is your "clearing time"). Be aware that it is the time it takes to clear the film that is important here. Exhausted fixer or fixer that has gone bad from age will still clear the film; just in a longer time.

When (or if) your fixer is exhausted (even partially), it will not (no way, no how) clear the film in the same time.

Now, how you want to apply your clearing time can be different. I like to fix my film for at least 3x the clearing time, especially if it is tabular-grain film (T-Max) since there are iodides in the film that take longer to fix than "conventional" films. Ilford and others say 2x. You can do the research and decide for yourself. In any case, I do a clip test with my partially-exhausted fixer before each batch and arrive at my minimum fixing time for that particular batch based on the (longer) clearing time in the used fixer.

In any case, when the clearing time for used (or unused old) fixer reaches 2x that in fresh fixer (your benchmark, remember?), the fixer should be discarded. It has been used too much or stored too long. Mix new fix. That's all there is to it.

If you have fixer that you suspect of not being able to fully clear the film, then you need to compare it to your benchmark clearing time. (If you haven't established that, then you should...)

If you fix film using these guidelines and add a bit of time for a safety factor (fixing slightly longer does no damage to film), you can be sure that your film is as fixed as it is likely to get after you have finished. The base will not be completely transparent; there is base fog and emulsion there. There may also be dyes that have not washed out completely. Modern films have stubborn sensitizing dyes in them that leave pink or blue casts to the base. This latter, however, has nothing to do with fixing; a slight color cast to the film will not affect printability or longevity.

Note that the above is for film. For prints a clip-test is less applicable, especially if two-bath fixing is used. Testing your workflow for residual silver (e.g., using the Kodak ST-1 test) is the best way. Using manufacturers' guides for throughput is the second best.

Best,

Doremus

Thanks for the detailed explanation. I don't know that I'm inventing a problem. I still like my test -- it's easy to do and tells me if my fixer is starting to fail. But your explanation makes me think there's something I don't understand (or misunderstood) about the clearing test. Why 30 to 60 seconds for that initial drop? I thought the clearing time test was meant to see how long it takes to clear the film to a degree established by that initial drop. But that can't be right.

Svenedin · Mar 24, 2018

I just dread to think what a visitor to apug/photrio would think. How anything so simple has to be dragged out to something so complicated is beyond ridiculous. There is another thread going about whether a developer to water proportion is 1 to whatever that is just as pathetic

bvy · Mar 24, 2018

Svenedin said:
I just dread to think what a visitor to apug/photrio would think. How anything so simple has to be dragged out to something so complicated is beyond ridiculous. There is another thread going about whether a developer to water proportion is 1 to whatever that is just as pathetic

There's nothing pathetic about wanting to learn and understand how things work. If you don't have an answer, we don't need to hear from you.

Svenedin · Mar 24, 2018

What exactly are you trying to “learn”?

Mainecoonmaniac · Mar 24, 2018

bvy said:
There's nothing pathetic about wanting to learn and understand how things work. If you don't have an answer, we don't need to hear from you.

Nope. Nothing wrong with wanting to learn how things work. It's always good to ask questions if one doesn't understand. I've been shooting film for decades and I still have a beginners mind. Photrio is an excellent source of info for me. Stay curious!

Sirius Glass · Mar 24, 2018

I fix film for twice the time to clear the film. If the film then has a blue, purple or pink tint, I fix longer. When it then gets to take long, I replace the hypo. [old school name for fixer]

Doremus Scudder · Mar 25, 2018

bvy said:
Thanks for the detailed explanation. I don't know that I'm inventing a problem. I still like my test -- it's easy to do and tells me if my fixer is starting to fail. But your explanation makes me think there's something I don't understand (or misunderstood) about the clearing test. Why 30 to 60 seconds for that initial drop? I thought the clearing time test was meant to see how long it takes to clear the film to a degree established by that initial drop. But that can't be right.

The point of the drop is to get a small portion of the film to clear before the rest. It is then more accurate to compare the later-clearing part to the area under the drop, which has cleared earlier. When there is no more difference between the two areas, the film is clear. Timing is done for the non-drop area.

What I think you are misunderstanding is that a clearing time for each film/fixer combination in fresh fixer needs to be established before further testing for clearing times using partially-exhausted fixer can be useful. How can you know when the 2x-time-in-fresh-fix has been reached if you don't have the 1x time? And, if you do the clearing test using fresh fix, you can be assured that your film is as fixed as it gets after 3x the clearing time, so you can see what the film-base+fog looks like for that particular film. Yes, you can make the base more transparent by bleaching out the fog, but that would bleach out the image too. Quit obsessing with the transparency of the film base.

@Svenedin: If you find this thread pathetic and/or ridiculous and a waste of your time, then simply don't post (you don't even have to read the thread...). Your need to tell me and others that we are dragging things out too far or beating a dead horse is superfluous. I'm willing to take the time to help newcomers and beginners understand things; sometimes it takes a while to get your mind around things. I appreciated the patience and dedication of my mentors and teachers, so I'm paying it back. I try to be helpful when I can...

Best,

Doremus

bvy · Mar 25, 2018

Doremus Scudder said:
The point of the drop is to get a small portion of the film to clear before the rest. It is then more accurate to compare the later-clearing part to the area under the drop, which has cleared earlier. When there is no more difference between the two areas, the film is clear. Timing is done for the non-drop area.

What I think you are misunderstanding is that a clearing time for each film/fixer combination in fresh fixer needs to be established before further testing for clearing times using partially-exhausted fixer can be useful. How can you know when the 2x-time-in-fresh-fix has been reached if you don't have the 1x time? And, if you do the clearing test using fresh fix, you can be assured that your film is as fixed as it gets after 3x the clearing time, so you can see what the film-base+fog looks like for that particular film. Yes, you can make the base more transparent by bleaching out the fog, but that would bleach out the image too. Quit obsessing with the transparency of the film base.

I'm not really obsessing with the transparency of the film base anymore -- at least as it relates to my original post. I understand now that ridiculously long fix times don't establish any sort of baseline for the clarity of the film base.

I appreciate you taking the time to explain all of this. I was apparently making some assumptions about the clearing test that weren't quite right. Thanks for "clearing" those up.

MattKing · Mar 26, 2018

FWIW...
From the "Fixer" portion of the section of the Kodak Alaris datasheet for T-Max developers titled "QUICK REFERENCE TO PROCESSING FILMS"
"Fix for twice as long as it takes the film to clear (lose its milky appearance); usually 2 to 4 minutes in liquid-concentrate fixers, 5 to 10 minutes in powder fixers."

Doremus Scudder · Mar 27, 2018

bvy said:
I'm not really obsessing with the transparency of the film base anymore -- at least as it relates to my original post. I understand now that ridiculously long fix times don't establish any sort of baseline for the clarity of the film base.

I appreciate you taking the time to explain all of this. I was apparently making some assumptions about the clearing test that weren't quite right. Thanks for "clearing" those up.

Happy to have helped.

A comment about applying clearing times: As fixer is used, the clearing time will increase due to loss of activity and, more importantly, build-up of dissolved silver from the fixing process. With used fixer, one should establish a new clearing time for the fix in its non-fresh state before each batch of film fixed.

As for the exact time used for fixing film: Both Kodak and Ilford say fix for twice the clearing time. There is evidence, however, that many modern films that contain silver iodide compounds are harder to fix and that three times (3x) the clearing time should be used. Others fix longer than 2x in order to clear the film of dyes. Fortunately, for film, fixing somewhat longer than absolutely necessary has no ill effects and does not affect wash times. So, I have standardized on 3x clearing time plus 10% or the maximum recommended time, whichever is greater, just to be certain that I've fixed fully and that the dyes are given ever chance to disappear. Example: Kodak says 2-4 minutes in Rapid Fix; my film clears in 75 sec. I'll fix for four minutes anyway. Sometimes even longer if the pink dye is stubborn, up to six minutes total. (I certainly wouldn't fix for less than the minimum recommended time in any case, regardless of the clearing time.)

And, when the clearing time for a used fixer reaches (or approaches) twice that in fresh fixer, it should be discarded. Note that this works fine for fixing film, but is not directly applicable to prints (especially fiber-base prints) since a film fixer can contain a lot more dissolved silver and still fix the film adequately. A print fixer is exhausted when much less silver is dissolved in it, meaning you can't use the "twice clearing time" rule for print fixer.

From the above you can see that I use clearing time primarily for determining when to discard a batch of fixer; for fixing times I always fix longer than the minimum to be safe.

Best,

Doremus

bvy · Mar 27, 2018

It was the 30 to 60 second thing that was throwing me. After I thought about it, the film clears to probably 75% in that amount of time and is enough to give the area under the initial drops of fixer a good head start. When the entire clip is then placed in the fixer, the area under the drops continues to clear and the surrounding area is trying to “catch up.” When the two areas become indistinguishable, it makes sense that the fixer has done all it’s capable of doing. If that happens quickly, the fixer must be good.

railwayman3 · Mar 27, 2018

FWIW, this has reminded me of the one time, as a schoolboy newbie to film processing, I left a film in the fixer overnight (no idea why, just seemed a good idea at the time...). Next morning a beautifully clear blank film and a little layer of black emulsion at the bottom of the tank.

CMoore · Mar 27, 2018

This is a Big FWIW and YMMV.......
I am still a beginner, so i am simply repeating "Common Knowledge", but.......i use Ilford Rapid Fix. I mix it 1:4
That is....One Part Fix and Four Parts Water.
I do not check very often anymore. When i started i always checked my film after the Two Minute mark. If it looked good (it always did), i went another Two Minutes.
I only use my Fix for one session...whether that be one roll or 6 rolls (35mm).
I shoot HP5 97% of the time, so i just assume the fix works fine every time. I still check, but not very often.
I dump the fix in a container and take it to our local college for disposal.
I do not reuse chemical for developing film
Especially as a beginner, It takes all of the guesswork out of the process for me. It certainly is not as economical as it could be, but the consistency is undeniable. I make enough mistakes with Exposure, Composition, Stupid human mistakes, etc etc.......i do not need anymore headache while trying to save a few dollars of chemicals.......

Mainecoonmaniac · Mar 27, 2018

CMoore said:
......i do not need anymore headache while trying to save a few dollars of chemicals.......

That's fine if economy is not your goal. But I hope you're don't dumping used fix down the sink. It contains silver. You may dump used developer down the sink.

CMoore · Mar 27, 2018

CMoore said:
.
I dump the fix in a container and take it to our local college for disposal.
.......

Mainecoonmaniac said:
That's fine if economy is not your goal. But I hope you're don't dumping used fix down the sink. It contains silver. You may dump used developer down the sink.

Fixing Overnight

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