Discussion in 'B&W: Film, Paper, Chemistry' started by Flauvius, May 11, 2008.
What are the signs of exhausted TF-4 fixer when looking at bone dry b&w negatives?
I had this happen to me just yesterday with my TF-4. Do your negatives have pinkish blotches in them? If so, your fixer is probably gone. That was how I discovered it. When I pulled the negative out of the fixer, the center of the negative was pink. I also have a little bottle of fixer tester that you can put a drop or two in the fixer and it indicates if the fixer is bad.
To test the fixer, you can put a piece of undeveloped film in a beaker of fixer (such as the cut off part of the 35mm leader) and it should clear in 30 seconds or so when you swirl it around.
As Jon Shiu mentioned, it should take about 30 seconds, or even 25, with fresh fixer to clear a test patch of film.
Someone from Ilford once told me to first place a drop in the center of a test patch of film. When it clears the silver emulsion, then drop the test patch into the fixer and agitate. Comparing the clearing film to the already cleared patch from the drop, it becomes very obvious when the film has fully cleared. When fix time doubles, it is time for a fresh batch of fixer.
I think that the pink casts will take longer to clear than the emulsions in most cases.
With TF-4, it is important to have fresh stock, and the stock solution should be used within the year. There are batch numbers on the bottle, and a call to Photographer's Formulary can tell you when yours was made.
I recently bought a bottle from my local photo supply store, whose owner assured me he had just got it in. But I was wary, and found out he had gotten it from a middleman. When I checked the batch number, I found out the stock was already several years old.
Now I order directly from Photographer's Formulary, and they send out fresh fixer.
Unless the fixer was totally zapped, I do not think problems would show up immediately on your negatives, but would over time.
If in doubt, I would fix my negatives again in fresh fixer.
For film, the best method for testing fixer capacity at home is the good old clip test mentioned above. Use the film(s) you are developing. Note the clearing time in fresh fixer (first placing a drop on the film as mentioned above helps in accurate visual assessment of the time). Keep track of the number of films processed, and when the number approaches the published maximum, do another clip test with the same film. When the clearing time in used fixer is twice that of fresh fixer, discard the fixing bath.
By extension, this can work for prints as well. I use film strips to keep an eye on the first fixing bath condition, discarding it when the film clearing time exceeds twice that of normal fixer. Of course, the second bath is never used to that extreme.
Manufacturers publish fixer capacities, and you should be aware of them, however, they are only rough estimates with a generous fudge factor built in for safety. Fixer is exhausted depending on the amount of undeveloped silver halide has been run through it, and this is impossible to estimate accurately since it depends on the amount of exposure and development (e.g. a dense negative/print will have less undeveloped silver halide than a very thin one). By using the clip test, you can get the most from your fix without exhausting it, since it shows the actual condition of the fixer.
There are solutions and strips for testing fixer (silver ion usually) and test kits for testing the fixed materials (residual thiosulfate) which are accurate, but best used as process controls, i.e. not every session.
Hope this helps,
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