Assessing underfixed negatives?

Discussion in 'Black and White' started by edward_isaac, Jan 8, 2014.

  1. Folks -- is there a way to assess whether already processed, rinsed, and dried negs have been properly fixed?
    I recently realized a batch of fix I had been using was pretty depleted, and a few rolls back had some magic shots that I don't want to deteriorate over time. But I don't want to re-fix if I don't have to, since it's a pain.
    Is there some visual clue, or a chemical test that can be easily applied on a sample neg (in the manner of the Hypo-check for liquid fix)?
    Thanks anyone/everyone.
  2. If the negs appear "milky" or "muddy" you should fix again. It isn't a pain. The pain is to give up some shots that could be good. Send a picture of your negs.
  3. "I recently realized a batch of fix I had been using was pretty depleted"

    This is one of the reasons I never re-use darkroom chemicals. Developer and fix go down the drain after each roll of film. Never any question of whether they are fresh.
  4. IMHO, throwing away fixer after a single use is a terrible waste of money and I'm sure many of us can't afford to be that extravagant.
  5. If they're only slightly underfixed, you might not see something for several years. I have a few from high school in this predicament. If I'd refixed them then (though I had no idea and this was 25+ years ago), they'd be printable now. As they are, they look cool, but not the way they should. If you're questioning it at all, you might as well just refix. That's better than always wondering.
  6. Thanks to those who have replied. The negatives in question look just fine, so I won't scan and post. Given the amount of film I process, I won't be discarding fix after every roll (which I find kind of nuts).
  7. Thanks, Bethe -- this is the kind of info I was hoping for.
  8. But I don't want to re-fix if I don't have to, since it's a pain.​
    Probably the easiest test, if you have a bit of clear film, perhaps on the film leader, is to partially refix. clip off a test piece then mark it about the halfway point. Perhaps use a "Sharpie" pen on each side, or even just scratch the film. Get it uniformly wet by immersing in water for a minute or two. Then, by hand, dip it in known-good fixer for 2 or 3 minutes, but ONLY HALFWAY, per your reference marks. Follow with a good rinse in water, then hang up to dry. After drying, view against a light-colored background, perhaps a lamp shade, or a brightly lie sheet of white paper. If the refixed part has become even the slightest bit more clear, then you know that the original fixing was inadequate.
    This test is only get for a gross deficiency. If you want a more sensitive test, kits are available. But all things considered, if you only have a couple rolls, it is probably less of a pain to refix (and rewash, etc.) than it is to purchase a test kit and go through the routine.
    The whole topic of how much to use your fixer can get complicated. Definitely the most economical method, from a chemical cost standpoint, is to use multiple stages and replenish it. But this is beyond most people's expertise and takes some time to operate and test. So a lot of small users seem to just use once or twice before discarding. (Industrial users could never do this, because of environmental regulations if nothing else.)
  9. Given the amount of film I process, I won't be discarding fix after every roll (which I find kind of nuts).​
    You might want to consider switching to a two-bath fix system. The basic idea is that the first bath does the majority of the "work," but is followed by a nearly fresh bath. Because the second bath will do the final "cleanup," it's ok for the first bath to approach "exhaustion." The net result is much lower fixer cost, as a percentage, while while the second ("clean") fixer bath assures complete fixation.
    There should be literature readily available, including from Kodak and Ilford, on using the method.
  10. Re-fix with fresh chemistry. There is no short cut for this if you are trying to save the images.
  11. A good rule of thumb for Ilford rapid fixer is 10 rolls of 36-exposure 35mm film per liter of film strength rapid fixer with high iodide content films like T-Max, more with other films. I've gotten up to 20 rolls with other films, but T-Max films tended to exhaust rapid fixer more quickly.
    And the fixer would fail rather suddenly, so it was easy to refix on the spot. The 11th roll of T-Max would take twice as long to fix and the 12th never would clear. It wasn't gradual so there wasn't any real guesswork.
    I mix two batches of film fixer: one for T-Max films; one for everything else. I put a bit of masking tape on the bottles and tick off each use. Easy to keep track of.
  12. Thanks again for all the helpful answers, esp. from the venerable members of the community. I guess I will just re-fix the things I absolutely don't want to lose. Kind of a no-brainer, eh? I'll see if I can attach one of them.
    The lesson for me is one of record-keeping. I know I should have been doing it from the beginning, but I've now got a log sheet pasted at face level in the darkroom where I write in the date I change chemicals, then log each roll I process. I tend to stick to HP5+, and avoid T-MAX, so that will make calculating the number of rolls I can process safely.
  13. You can also periodically test your fixer. Do this test when you first mix your fixer to get a baseline, always use the same film for consistency and when the time is double your baseline then look at replacing your fixer.
    Test: Put an ounce or two in a clear cup, cut a small piece of film about an inch long, put a drop off fixer on the emulsion side and start timing. When 30 seconds has passed drop the piece of film in the cup and continue timing. When you can no longer see the dot, note the time.
    Now you can use this test to determine how long to fix for, for different films. For regular or older emulsions, like Tri-X, FP4+, you fix for 2 times the time it takes to clear, for tabular films or modern style films like Delta 100 and Tmax, you fix for 3 times the time it takes to clear.
  14. OK since you seem to have solved/resolved my initial question, here's a follow up: how long after initial fix can you usefully re-fix? A few days? A month? Two years? To prevent (further) deterioration. Thanks, all.
  15. I use the two-bath fixing method and have done now for many years. This guarantees complete fixing.
  16. The usual rule if fix for twice the clearing time. If you notice any whiteness to the clear parts, refix.
    Sometimes while I am fixing, I put a scrap of film in some of the fixer and time it.

    The problem with overused fixer is silver thiosulfate complex left in the film. But it also clears slower, so usually you would notice.

    But it isn't that hard to put it back on the reel, fix, and rewash it.

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