What is "pyro" developer?

[robert himmelright]

What exactly is a "pyro" developer. I keep reading things about how amazing

these "pyro" developers are, but can't gather any real information.

[jay_de_fehr]

Pyrogallol was one of the first developing agents, and was dominant until metol/hydroquinone were introduced. In a low sulfite environment, pyrogallol produces a stain in proportion to the silver image density, and tans/hardens the emulsion proportionally. Staining and tanning are useful characteristics and can be exploited to enhance image definition, and improve the printing quality of a negative. Traditional pyro developers were problematic, due in part to the requirement for low sulfite, which led to pyro developers being made in three separate solutions, or in solutions that were made up fresh from bulk chemicals, and used one-shot, both approaches caused various problems of convenience and of disparate keeping properties of the various solutions. I've written a short introduction to my own, modern staining developers here:

 

http://www.digitaltruth.com/techdata/article-stainingdev.php

 

It is hardly comprehensive, but might prove a useful primer.

 

Jay

[don_mckeith]

I haven't used pyro, but I have used Gallic acid, which will develop an albumen(ortho) glass plate in 45 minutes--give or take(usually give 15 -30 min).What is gallic acid you ask? It's made from the Chinese gall nut. don't ask--

 

http://www.mfa.org/_cameo/frontend/material_description.asp?name=gall&language=1

 

http://www.1911encyclopedia.org/G/GA/GALLS.htm

 

 

eventually some genius figured out that if you heat(pyro) gallic acid,

the chemical properties change( I'm not a chemist-don't know)and you could develop a glass plate(ortho) in 5- 10 min.

 

fast foward a 100 years or so, some genious(a different one)figured out that the stain that "pyro" imparts on modern film has some advantages--I think mostly in the "ALT Process" end of the spectrum.

[mikem77]

They aren't "amazing". I tried out Pyrocat but went back to HC110. The differences were too subtle for me to put up with the extra safety precautions needed for Pyrogallol developers.

[photojim]

Hydroquinone, which is an ingredient in many developers, is a close relative of pyrogallol and shares much of its toxicity.

 

You can only know if you like pyrogallol developers if you try one. To me, the best feature of PMK (my favourite pyrogallol developer) is its 5-year-plus lifespan as a stock solution. It also makes pretty negatives.

[sandy_king]

The following article was written in part to answer this type of question.

 

http://unblinkingeye.com/Articles/PCat/pcat.html

 

Sandy

[discpad]

OK Sandy, I went through your entire 4 page article on Pyrocat-HD, and noticed on page 2

http://unblinkingeye.com/Articles/PCat/PCat2/pcat2.html

 

that you recommend adding 300mg/liter sodium sulfite to the working solution to eliminate oxidation when using a Jobo processor:

 

1) Wouldn't adding 30 g/liter of sodium sulfite to stock solution A (the same amount that would be in 1:1:100 working solution) be better, since it will act as a preservative of stock solution A?

 

2) Since general stain is caused by aerial oxidation, shouldn't the sodium sulfite be mandatory for all processing methods?

[sandy_king]

Dan,

 

I don't recommend adding extra sulfite to the stock solution because there is really is no need for it except when all three of the following conditions are met.

 

1. Rotary development at high RPM.

2. Use of a high speed or thick emulsion film that tends to develop a lot of B+F. BPF, JandC 200 and 400, etc.

3. Development times are very long in order to reach necessary CI for AZO 2 and alternative processes.

 

However, even in the above circumstances, which will not be encountered in the great majority of situations, my recommendation today (the article was written some 4-5 years ago) would be to simply add more of Stock A when mixing the working solution, i.e. instead of the 1:1:100 dilution use 1.5:1:100, or instead of the 2:2:100 dilution use 3:2:100. Do this rather than increase the amount of sulfite. The reason is that pyrocatechin based developers are highly sensitive to sulfite and if you add to much you kill the stain.

 

Sandy

[jay_de_fehr]

All pyro developers are not created equal, and there is a distinction to be made between pyrogallol developers and catechol developers. Catechol developers work at a higher pH than pyrogallol developers, and are more sensitive to sulfite. Pyrogallol produces more robust image stain than catechol, and I don't know of any single solution, staining catechol developers. In short, pyrogallol is the king of staining developers. Over the last century, pyro developers earned a reputation for inconsistency, speed loss, coarse grain and toxicity, but with the introduction of 510-Pyro, that reputation is no longer accurate, or deserved. 510-Pyro is as easy to use as any developer, and more so than many, gives full film speed+, extremely fine grain, and dead consitency from one working solution to the next, plus, the stock solution will last decades on the shelf. 510-Pyro is unlike any other pyro developer, not at all like any catechol developer, and works equally well in tanks, trays or rotary processors without altering the formula. Those who believe that PMK Pyro represents the state of the art in pyro developers are sure to be surprised if they try 510-Pyro, as are those who believe pyro developers to be a poor choice for fast, 35mm films.

 

Jay<div></div>

[discpad]

But...

 

Pyrogallol is more than twice as expensive as catechol...

[jay_de_fehr]

...and worth it. It's really a non-issue considering that 100ml of 510-Pyro contains 10g of pyrogallol ($1.65)and will develop 100 rolls of film. At that rate it makes Rodinal look very expensive by comparison.

 

Jay

[jeff_de_lamarre]

I tried the PMK developper for the first time a month ago. I was very happy about my negs, very sweets and charming. After a month I re-developped two films and they appear transparent. I am very irritated about that, I was told the PMK was excellent about stocking, but I read too PMK is very fragile about contamination with other chemistry. This already happens to someone ? I really want to continue with PMK but if I don't get sure about stocking, I'll go back to traditionnal ways.

Thanks

 

JF