pyro developer, but which?

[tbeaman]

You often hear the advice to use gloves, but rarely is it specified which kind. Are the thin nitrile or latex ones satisfactory, or is it better to step up to some kind of thicker rubber? Dishwashing gloves? What about my wool winter mittens? There's all kinds of them out there.

[imagedowser]

The Darkroom Cookbook, 3rd edition, Anchell... index:" Pyro. see pyrogallol (pyro) " The Negative, Adams... Index: "Pyro (pyrogallic acid, pyrogallol)" Both index listings are followed by Pyrocatechin as a separate listing. I've been processing film since 1950 and my understanding is pyro is pyrogallic acid, pyrocatechin is not... I don't own a photographic dictionary but I bet it's in there with pyrogallic acid as the primary meaning.... First thing you learn in stress reduction is not to HAVE to be right... hate to loose anyone over a pissing contest on developers.

[Vlad Soare]

Pyrogallol is 1,2,3 tri-hydroxy-benzene.
Pyrocatechin, or catehol, is 1,2 di-hydroxy-benzene.
They are not the same thing.
"Pyrogallic acid" is an improper name for pyrogallol (which is actually not an acid).
The short name "pyro" usually refers to pyrogallol, though the syntagm "pyro developer" is sometimes used for designating all staining developers in general.

You often hear the advice to use gloves, but rarely is it specified which kind. Are the thin nitrile or latex ones satisfactory, or is it better to step up to some kind of thicker rubber? Dishwashing gloves?

Right now I'm using unpowdered nitrile gloves. Before discovering these, I used to use regular latex surgeon's gloves from drug stores, but I didn't like them because they were powdered, and everything I touched remained white. Dish-washing gloves are fine from a safety point of view, but I think they're too clumsy for the kind of work required in the darkroom.

[tbeaman]

Pyro is just a shortform colloquialism, and both of those chemicals start with "pyro". I can see how it might be confusing or not matter for those not of the cloth.

Can't Pyro be an umbrella term for both? They're not all that incredibly different anyway, and where they are, it doesn't seem any more substantial than the differences between developers within other categories.

Right now I'm using unpowdered nitrile gloves. Before discovering these, I used to use regular latex surgeon's gloves from drug stores, but I didn't like them because they were powdered, and everything I touched remained white. Dish-washing gloves are fine from a safety point of view, but I think they're too clumsy for the kind of work required in the darkroom.

I agree, that's why I wondered about the nitrile/latex. Thanks.

[matthew klos]

I posted on here awhile ago talking about my problems with pyro i have since worked out the kinks. I shoot FP4 and i develop in PMK, and it works very nicely for me. For the project i am working on i have been shooting with a hasselblad and with direct flash, and i find the pmk does wonders for skin tones. It works for me.

[Vlad Soare]

Can't Pyro be an umbrella term for both? They're not all that incredibly different anyway, and where they are, it doesn't seem any more substantial than the differences between developers within other categories.

Interestingly, catehol is closer to hydroquinone than to pyrogallol. Hydroquinone is 1,4 di-hydroxy-benzene. They're almost the same, it's just the position of a hydroxyl group that differs.
Catehol and pyrogallol behave quite differently. The only thing they have in common is that they're both staining developing agents. But then, so can be hydroquinone.

I think it's best to be aware of the differences and to always call them by their proper names. This way we'll avoid any confusion, particularly among people who are new to staining developers and/or have no background in chemistry.

[sanking]

Catehol and pyrogallol behave quite differently. The only thing they have in common is that they're both staining developing agents. But then, so can be hydroquinone.

Actually both pyrocatechol and pyrogallol are staining *and* tanning developers. The tanning quality is in my mind more important than staining since it is tanning that makes these developers sharper than traditional developers.

I am not sure what you mean by when you say that catechol and pyrogallol behave quite differently. There are some differences to be sure but in my experience the two reducers actually behave very much alike. They both stain in the absence of sulfite or ascorbic, they both tan gelatin, and they both produce oxidation by products that can create B+F stain if the formula is not well balanced.

Sandy

[sanking]

Can't Pyro be an umbrella term for both? They're not all that incredibly different anyway, and where they are, it doesn't seem any more substantial than the differences between developers within other categories.

If a developer stains and tans I place it in a category called Pyro staining and tanning developers, regardless of whether the reducer is pyrocatechol, pyrogallol, or hydroquinone (which can also stain and tan in some conditions).

Sandy King

[Vlad Soare]

Actually both pyrocatechol and pyrogallol are staining *and* tanning developers.

Indeed, they're also tanning. I keep forgetting that. My mistake. But this has nothing to do with the fact that pyrogallol and catehol are two different chemical compounds, with different physical and chemical properties, which should be called by their proper names to avoid any confusion.

I am not sure what you mean by when you say that catechol and pyrogallol behave quite differently. There are some differences to be sure but in my experience the two reducers actually behave very much alike.

I don't have your experience with formulating developers, so I'm not going to contradict you here. My impression was that if one were to roughly describe them, one could say that pyrogallol tends to give coarse grain, lower film speed, a pronounced toe, and yellowish-green stain, while catehol, especially in conjunction with phenidone, tends to give fine grain, good film speed, a shorter toe, and brown/reddish stain. But of course this depends a lot on the overall formula, and if you're saying they are really so much alike, then I have no reason not to believe you. Do you think you could make Pyrocat work the same by replacing catehol with pyrogallol, without making major changes to the rest of the formula? I'm not trying to provoke you, I'm genuinely interested.

[Drew Wiley]

Gloves: For chemcial mixing and general dkrm activities I prefer slightly loose-fitting
thicker nitrile gloves, which can be taken on and off easily and aren't fragile. For actual
film hanling and tray development, I use thin disposable non-powdered (but textured) nitrile gloves. Nitrile is now priced barely higher than latex, and is superior is many ways. PYRO: I've tried quite a few different formulas and even concocted a couple of
my own, of both pyrocat and pyrogallol. The pros and cons are subtle but worth knowing. The color of image stain can be important with respect to a particular light
source and type of paper (VC vs blue-sensitive). Performance on long-scale contact
media vs ordinary silver projection papers also is a significant factor in the opinion about which "pyro" is "best" for what. But most of the popular options are in my own
"non-humble" opinion going to give much more easily printable negative than conventional "non-pyro" developers. Well worth learning the ropes. I'd probably start
with something with a lot of background info readily accessible, like Gordon Hutchings
PMK formula or one of Sandy's popular pyrocat ones.