Processing 510 Pyro & 100TMX with Jobo CPP-2

I also use a respirator when I tray process with pyro simply because it is an acidic developer that can emit an odor no different than when I mix stop bath from glacial acidic acid. The concentrations are dissimilar, but the concept is the same. With pyrocat the dilution used are so minor that the respirator is not necessary. A gallon of pyro will get me thee months of use whereas I can get as much as 18 months plus out of a gallon of pyrocat. And yes, both need to me mixed outdoors with the full suite of protective equipment listed above.

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Originally Posted by Michael R

Pyrogallol is a dangerous compound, and few home-brewers know what they are doing.

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And it has no qualities that cannot be matched by less toxic means. The only reason Kodak had for its use by the 1950s/ 60s onwards was for tanning unhardened matrix emulsions - and even then, they had active research into its replacement there until basic Dye Transfer research ended in the mid 1960s. A lot of the time the current use of pyro and the like seems as much about conspiracist denial of the major manufacturers' very considerable basic research in favour of some sort of bizarre macho performance to patch over artistic (and other) inadequacies via the loudly trumpeted use of a needlessly toxic substance.

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Originally Posted by interneg

And it has no qualities that cannot be matched by less toxic means. .

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Would be elated at qualifying this assertion as I have put at least a dozen less toxic alternatives to the test over the last 20+ years and nothing even comes close to pyro from my visual perspective. I have come to terms with the reality that its toxicity is easily manageable. But at the end of the day the end justifies the means hence the reason that I continue to use it in large quantities.

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Originally Posted by koraks

* Oxidation of the concentrate turned out far worse than online reports indicated, resulting in unpredictable activity once the concentrate was more than a couple of weeks old

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Which grade TEA did you use? Lower grade TEA contains some water which can potentially influence the shelf-life of the concentrate.

Of course there's some water in my TEA. Pure TEA is a solid at room temperature. Do you weigh your TEA by cutting blocks off it or do you pour it without having to heat it first? In case of the latter, there's also water in your TEA.

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Originally Posted by Michael Kadillak

Would be elated at qualifying this assertion as I have put at least a dozen less toxic alternatives to the test over the last 20+ years and nothing even comes close to pyro from my visual perspective. I have come to terms with the reality that its toxicity is easily manageable. But at the end of the day the end justifies the means hence the reason that I continue to use it in large quantities.

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What do you perceive as being the behaviour of negatives developed in pyro (which formulae?) or Pyrocat? Much of Pyrocat's supposed qualities really owe more to being fortuitously coincident with known PQ characteristics than anything special. Added to that, a degree of solvency seems to be important to achieving optimal sharpness with modern (i.e. 1950s onwards) emulsions.

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Originally Posted by interneg

What do you perceive as being the behaviour of negatives developed in pyro (which formulae?) or Pyrocat? Much of Pyrocat's supposed qualities really owe more to being fortuitously coincident with known PQ characteristics than anything special. Added to that, a degree of solvency seems to be important to achieving optimal sharpness with modern (i.e. 1950s onwards) emulsions.

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The only metric that need be in play is in the print. Pyro and pyrocat HD (in reduced agitation mode) have a discernible edge effect and mid tone separation that is simply unparalleled. At the end of the day the print is all that matters.

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Originally Posted by Michael Kadillak

The only metric that need be in play is in the print. Pyro and pyrocat HD (in reduced agitation mode) have a discernible edge effect and mid tone separation that is simply unparalleled. At the end of the day the print is all that matters.

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Very little of that's likely to be the pyro. Of either sort. The useful pyro effects seem to be largely restricted to emulsion tanning in unhardened emulsions.

It seems (from the available industry literature - at the engineering/ research/ academic level - not the relatively popular market books that come to a halt in disclosable knowledge somewhere between 1950/1960) that in those developers, it's largely Metol exhaustion effects or Phenidone byproducts causing development inhibition that produces the observable edge effects. Adding an effective source of electron replenishment (e.g. HQ/ AA/ HQMS etc - and this seems to work even outside conditions that might be characterised as 'superadditive' - even though superadditivity is not as clear-cut as home-brewers assume once any emulsion addenda come into play) will largely switch off the effect in MQ developers, but can be exploited in PQ type developers to produce radically differing levels of the effect. If you strip out the pyrogallol from various staining developers what you're largely left with are bowdlerised Beutler (which produces high sharpness both microdensitometrically and perceptually) derivatives - or accidentally functional PQ relationships - and that one of the isomers of HQ seems to behave sufficiently like it in specific formulae, just producing a slightly different dye. The research wasn't purely microdensitometric, it involved large quantities of double blind print testing - which found that adjacency effects had to be balanced against granularity - and that extremely strong adjacency effect producing developers (POTA) could produce markedly unpleasant prints. By using non-solvent developers the ability to access the Bromide & Iodide placed in the emulsions to produce sharpness enhancing adjacency effects through development inhibition is left unused as well - and it is in accessing the Br and I that D-76 and ID-11 are able to deliver remarkably sharp results - if basic process controls are instigated. The other aspect that is often ignored is that a pH of around 10 seems to maximise sharpness. If you put all these together, you can zero in on potential candidate developers. In other words, an appropriate ratio of P:Q (or AA etc), some solvency and carbonate buffered to just under a pH of 10.

From microdensitometric study we also know that the visually perceivable effects of anything more than nil agitation effectively boil down to differences in overall contrast with no meaningful impact on sharpness measurable or perceivable (when the experiments are properly controlled) - with possible exceptions for litho film in litho developer in specific situations. In other words all that is happening is that the developers you are using & how you are using them is probably widening your margin of error against overdevelopment for the grade you want to print on and possibly underexposure. I've had enough staining developer outcomes through my hands to feel that it's pretty obvious to me why the manufacturers with large basic research capacity, never mind significant organic chemical synthesis resources, seem to have stopped research on staining developers a long time ago. DIR/ DIAR couplers (and research into how to potentially get similar effects from regular B&W emulsions through new emulsion making approaches) were able to deliver effects that many assume their magical-developer-recipe-silver-bullet is delivering (even though it isn't).

Metol is also poisonous, in case this conversation is giving anyone the impression it isn't.

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Originally Posted by martiansea

Metol is also poisonous, in case this conversation is giving anyone the impression it isn't.

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All photochemicals should be treated with care and can be harmful if you are stupid in handling them, but of the regular chemistry you are likely to encounter Pyrogallol is particularly potentially dangerous (skin absorption along with all the other risks). Like unsubstituted PPD, there's not really a good reason to use it (unless you absolutely need to tan an unhardened emulsion).