I've been using TF-3 (Anchell's Darkroom Cookbook recipe) for years for printing on Ilford MG Fiber paper. Some recent batches of the ammonium thiosulfate solution used in TF-3 arrived with, or since thrown, a white precipitate. I assumed that this was just colloidal sulfur and would cause no problems provided that the prints were well-washed, which they are.

I did some local bleaching with a dilute ferricyanide solution, followed by another fixing in fresh TF-3. After washing and drying the prints, I noticed that the areas I bleached had a whitish haze in the dark tones which is apparently in the emulsion itself, not on the surface, since it cannot be wiped off. I speculate that the ferricyanide reacted with the TF-3 and caused the white precipitate to form in the gelatin. I have never seen this effect before after doing local bleaching.

To be exact, my process was as follows:

Develop in D-72
Citric acid stop bath
Two-bath fixation in TF-3 (2 liters each)
Wash for one hour

I assume that the citric acid in the stop bath gradually neutralizes the alkali and sulfite in the TF-3, but I make fewer than 10 11x14's in a session and throw the first bath out at the end. In the past, I've never noticed the first bath getting murky while using it, but the thiosulfate solution I used in the past was never murky to begin with.

In the bleaching in toning session I followed this procedure:

Soak the prints in water
Put the print to be spot-reduced in fresh TF-3 for one minute
Move the print onto a sheet of acrylic and mop it off with a sponge
Spot-reduce with ferricyanide solution
Put the print back in the TF-3 and evaluate
Repeat previous three steps if needed
Rinse in running water for 30 minutes
Tone in selenium
Wash for one hour

I don't know the exact concentration of ferricyanide that I use but it's probably close to 0.25 to 0.50 percent or less. It works slowly enough for me to control it.

The above process left me with the hazy whitish-blue fog in the dark tones. It is the same process I've used successfully for years. In fact, there was quite a bit of the white precipitate left in my sink the next day.

I'm guessing that in order of likelihood, my problem was caused by one or more of (1) a bad batch of ammonium thiosulfate solution; I should not accept murky product in the future; (2) I let the thiosulfate spoil by letting it sit around in the vendor's bottles for 6 months or more, some bottles not full (but even the unopened bottles have schmutz on the bottom of them), or (3) the thiosulfate (sitting on the concrete floor as it does) probably spends a lot of time at 50 deg F or less during the winter months (I keep the darkroom at 55 deg F when I'm not using it) and that's too cold to store thiosulfate solution, or (4) something else.

Any ideas?

Separately, since my printing volume is so low these days, I've been thinking of chucking TF-3 entirely and using Kodak Rapid Fixer (without the hardener) or Ilford Rapid Fixer solution instead. I assume that these are both alkaline fixers. Do the concentrates keep well in partially full bottles? Any reason to prefer one versus the other?

Thanks in advance for your suggestions and advice.