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I wonder if there are any detrimental effects with increased alkalinity - for instance, as you increase pH from about 6 to about 9. PE has mentioned increased emulsion swelling, which probably corrects itself after drying, but I'm not sure what other effects this and anything else that happens may have.
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Use of pH values above 8 should use a hardener fix. At pH 9 or above, swell becomes so great that you risk reticulation. At that point, Kodak used Alkaline Hardener Fix (AFHF) or Alkaline Formalin Hardener Fix.
PE
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 Originally Posted by Photo Engineer  Thiourea comes to mind here. It is smaller than thiosulfate and so like ammonia can increase diffusion rate and also it is synergistic with hypo increasing fixing rate. Being non-ionic, thiourea helps in other ways too. Thiourea, even though it has a long history with toning, is a chemical I try to avoid. It has a Contact Rating: 3 - Severe (Life). It is anticipated to be a carcinogen - in response to that the State of California has declared it to be carcinogenic.
Probably best to avoid the use of it if you can.
Kirk
For up from the ashes, up from the ashes, grow the roses of success!
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BTW, about the stop bath, for FB printing, I happen to use a buffered one (pH +/- 5,5) in combination with a two bath C-41 fixer (FUJI's Unilec pH +/- 7,5). The first fixer bath goes down to pH 6 à 6,5 after a while, but the second one stays at around pH 7. As a HCA, I just plunge the paper, after a short wash, in 2% Sodium sulphite for 2 min. before I process it in KRST 1:10 for an other 2'. No problems so far.
I think that a buffered stop has more 'respect' for a neutral to alkalic fixer. And the stop bath can be replenished by topping off, and this kind of fixer lasts longer too, so less dumping into the environment. This, of course, does not mean that this is a match better way of 'acting' nor is it the Holy Grail, but worth considering, does it?
Philippe
"...If you can not stand the rustle of the leafs, then do not go in to the woods..."
(freely translated quote by Guido Gezelle)
PS: English is only my third language, please do forgive me my sloppy grammar...
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Originally Posted by Peter Schrager OK Dan you got me....what is the formula for TF2?? is it in the
cookbook? I'll go look now....for papers I use the michael smith
fixer formula....
it's way cheaper to buy 25 pounds of NaThiosulfate and add
the bisufite fresh for the printing session... The TF-2 formula:
Sodium thiosulfate-sulfite-metaborate, 250-15-10
grams. Water to make one liter. Likely in the cookbook.
Similar to Adam's plain fix save for the metaborate. That
250 is the penta hydrate; 160 for the anhydrous.
Additions of bisulfite will lower the ph. The Michael Smith
formula? What might that be? Dan
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smith formula
Dan-that formula is strictly for papers....one pound of thiosulfate; 15 grams of sulfite and 64 oz. water....thank you for the TF2 formula and it is not in the cookbook; at least the older edition
Thanks, Peter
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Originally Posted by Kirk Keyes Thiourea, even though it has a long history with toning, is a chemical I try to avoid. It has a Contact Rating: 3 - Severe (Life). It is anticipated to be a carcinogen - in response to that the State of California has declared it to be carcinogenic.
Probably best to avoid the use of it if you can. I merely mention it, however for CA residents to comply with the regulations there, they must be aware that a lot of their flowering plants must be removed! 
Thiourea, as well as urea are metabolic byproducts of a lot of plants and animals.
PE
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What I love about TF-3 is being able to selenium tone test strips and work prints without having to wash after an acid fix, then re-fixing in plain hypo. Toning can sometimes have dramatic effects, especially in clouds, so it's a real time saver being able to go straight from the TF-3 into the selenium toner while trying to nail a print.
Murray
_________________________________________
Note to self: Turn your negatives into positives.
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Originally Posted by Photo Engineer IThiourea, as well as urea are metabolic byproducts of a lot of plants and animals. The most reputable source I could find is a report by the World Health Organization, http://www.inchem.org/documents/cica...icad49.htm#4.0,
"Thiourea has been detected but not quantified in laburnum shrubs (Laburnum anagyroides) and is a natural metabolite of the fungi Verticillium alboatrum and Bortrylius cinerea (IARC, 1974)."
I guess I don't have to worry about eating much of those two things.
I just mentioned it as ammonium thiosulfate is pretty safe and very fast acting, either in alkaline, or near neutral/slightly acidic pH ranges.
I understant there are markets or uses where speed is the upmost importance, but for the typical home darkroom worker, it seems a bit overkill to use compounds that are suspected carcinogens in the place of compounds that do not have those properties.
Kirk
For up from the ashes, up from the ashes, grow the roses of success!
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Originally Posted by MurrayMinchin What I love about TF-3 is being able to selenium tone test strips and work prints without having to wash after an acid fix, then re-fixing in plain hypo. I do this with Ilford Hypam. Dev, stop, fix, and then into fix with selenium toner, quick water rinse, wash aid, and then wash.
It works fine without an alkaline fix.
Kirk
For up from the ashes, up from the ashes, grow the roses of success!
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