TF-4 User For Years...Want To Try TF-5

[Doremus Scudder]

Doremus, just some things to keep in mind which make direct comparisons difficult:

1. Different assumptions regarding acceptable final amounts of retained thiosulfate/silver-thiosulfate complexes in the paper for different levels of permanence.

2. Initial concentration of thiosulfate per litre of working solution, although similar, may not be the same

3. The allowable concentration of silver depends to some extent on fixing time assumptions. For example, Kodak suggests a capacity for its rapid fixer of ~25 8x10s/litre working solution at half the concentration of the dilution for film fixation (so more prints than Ilford, and at a lower concentration than Ilford) but with much longer fixing time.

4. Capacities based on the silver content of the fixing bath are basically assuming these are insoluble complexes. However there are compounds which can be added to a thiosulfate fixer which can increase the solubility of fixing by-products. There was research into this at Kodak etc. mostly in the context of rapid access processing. Some of the more obvious ones have potential downsides such as gelatin softening but Ron hinted at others. TF5 and TF4 do contain additional ingredients not present in standard rapid fixers, and these may (or may not) affect throughput capacity.

5. Besides Ilford’s thoroughly disclosed research into fixing times and washing with respect to permanence, manufacturers’ instructions are basically “black boxes”. Rely on them or don’t. We know companies like Kodak did the work, so taking their recommendations at face value is sensible. Other companies? Not as clear. There’s probably some extrapolation going on, but that isn’t necessarily unreasonable. After all, fixation of photographic materials is quite well understood and has been around for a very long time.

I would say whenever venturing into non-Ilford/non-Kodak fixers, some testing (including wash results) is probably wise. Simple stuff like retained silver etc. Or, simply apply Ilford’s instructions. They are the most conservative, so things are unlikely to go wrong.

Thanks Michael,

Yeah, I'm aware of all the parameters you mention. It's just that I don't know enough about fixer formulation and the complex chain of reactions that end up producing the soluble argentothiosulfate compounds to be able to assess capacity claims for various fixers from different manufacturers. That's why I've always used Kodak/Ilford products, assuming that their research is thorough and sound. When capacity claims for other, ostensibly similar, fixers don't jibe with the capacity claims from Kodak and Ilford, and when there's no reference to any research backing up those claims, I get a bit skeptical.

For example, the TF-5 instruction sheet makes no reference to what standard of fixation is being targeted (vs Ilford's "commercial" and "optimum permanence" standards). One could assume that such a product was designed for "archival" processing, but if so, then why is the capacity listed three times that of the Ilford fixers? If a product really is superior, one would think that the manufacturer would want to demonstrate that to the potential customers. Not doing so makes me think that there's nothing behind the claims.

If/when I get around to switching to TF-5 or whatever, I'll just have to do my own throughput capacity tests using ST-1 or the KRST tests. I've done this for the Ilford products, so, unless I suddenly feel like testing out a new fixer just for the fun of it, I likely won't be changing from Ilford anytime soon.

Best,

Doremus

[Michael R]

Makes sense to me. Like I said, Ron didn’t write the stuff on the PF site for TF-5.

Thanks Michael,

Yeah, I'm aware of all the parameters you mention. It's just that I don't know enough about fixer formulation and the complex chain of reactions that end up producing the soluble argentothiosulfate compounds to be able to assess capacity claims for various fixers from different manufacturers. That's why I've always used Kodak/Ilford products, assuming that their research is thorough and sound. When capacity claims for other, ostensibly similar, fixers don't jibe with the capacity claims from Kodak and Ilford, and when there's no reference to any research backing up those claims, I get a bit skeptical.

For example, the TF-5 instruction sheet makes no reference to what standard of fixation is being targeted (vs Ilford's "commercial" and "optimum permanence" standards). One could assume that such a product was designed for "archival" processing, but if so, then why is the capacity listed three times that of the Ilford fixers? If a product really is superior, one would think that the manufacturer would want to demonstrate that to the potential customers. Not doing so makes me think that there's nothing behind the claims.

If/when I get around to switching to TF-5 or whatever, I'll just have to do my own throughput capacity tests using ST-1 or the KRST tests. I've done this for the Ilford products, so, unless I suddenly feel like testing out a new fixer just for the fun of it, I likely won't be changing from Ilford anytime soon.

Best,

Doremus