Formulary PMK Pyro fixers TF4 vs TF5

The Formulary recommends TF4(alkaline), but I regularly stock & use TF5(ph neutral). It seems to me that TF5 should be fine given that there's a final, subsequent soak in the expended developer which should provide the right ph to develop the stain. Right?

Most practictioners have eliminated the post-fixing staining bath. It was found that the proportional staining happened during development and the post-fix staining was more general and tended to just increase exposure times without increasing contrast or otherwise contributing to the print.

I suggest skipping the staining bath, try the TF5 and see how it looks and prints for you. Do a post-fix bath on an otherwise identical film/image and compare.

Others have used Pyro developers and acid fixes with success, so there is room to explore.

Either work with or without staining.

I've used TF4 and TF5, various standard rapid fixers, and non-hardening thiosulfate fixer that I mix myself with PMK, Pyrocat-HD, and WD2D and have never seen any issue with the stain. I, too, would recommend eliminating the after-bath of used developer. IIRC, Mr. Hutchings has stated that it's not necessary.

Fixers used to be a lot more acidic in past times. It is well known, that strong acids dissolve oxidized and polymerized developer stains, so it's quite possible, that a hardening fixer at pH 4.5 will also remove some wanted pyro stain. Evidently this does not happen at higher pH, and from what I read here, that limit appears to be somewhere above pH 5.5.

I use regular old Ilford Rapid Fixer or Hypam at the 1+4 dilution for PMK-developed negatives. Zero problems; staining is just fine. TF-5 should work fine too.

Doremus

Rudeofus said:

Fixers used to be a lot more acidic in past times. It is well known, that strong acids dissolve oxidized and polymerized developer stains, so it's quite possible, that a hardening fixer at pH 4.5 will also remove some wanted pyro stain. Evidently this does not happen at higher pH, and from what I read here, that limit appears to be somewhere above pH 5.5.

Click to expand...

This is the first time that I've read that a rather acidic fixer has a benefit in addition to being the necessary environment for hardeners to work. I have been using a fixer around neutral pH (in order to accelerate washing of FB paper) and for a time I used running water instead of an acid stop bath. Fixer was two bath with small throughput. I did experience some staining well after fixing and drying. I found that an acid stop prevented this from happening.

I wonder that if I had used a fixer like Ilford Rapid Fixer, I might not have experienced staining even using a water rinse instead of acid stop.

(I will continue to use an acid stop, just wondering)

I've standardized on TF4 for a long time. The alkalinity seems to work better at removing any residual antihalation dye stain, although complete removal occurs during the washing stage. Such residual dye might not be apparent on a pyro stained neg, but still has some effect. But it's in color masking work that it's least welcome; and I don't want to be bothered with different fixers for different projects. TF4 is also my standard print fixer, and saves a lot of time and fuss there.
An alkaline afterbath in relation to pyro stain is redundant, as others have already explained. It just increases overall fbf staining, and is not proportional like development staining. My attitude at this point is, If it ain't broke, don't try to fix it. In other words, TF4 works well for me. But it would be interesting to hear experiences about TF5 too.
You don't need a hardener with pyro negs. It's a tanning agent, self-hardening. But I have never found the need of a supplemental hardener with any kind of film. And with respect to stop baths, with certain films very sensitive to this like Efke 25, I employed stops so weak that it might as well have been plain water. Made no difference with respect to the pyro effect.

TF4 is a headache to stir up if the gallon jugs have sat around a long time. I decanter off some of the liquid then put a long wooden dowel in there to release and stir up everything stuck to the bottom. Then I shake it well and add back the remaining fluid. Once some of the fixer has been used, enough air space will remain in the jug to more easily shake it up the next time. It is a concentrate of course. Odor no big deal unless you're darkroom is unventilated, which would be an undesirable scenario regardless.