Pyro formulations for JOBOgreenspun.com : LUSENET : Large format photography : One Thread
Photographers Formulary and Bosick & Sullivan both make pyro kits designed for rotary processors. I was talking to someone who said that the B&S rollo pyro is best because it contains citric acid which will prevent excessive build up of stain base fog (uniform stain density forming regardless of silver development). Their comment may have been made assuming I was going to use PMK in the JOBO and they may not have known about the PF ABC pyro formula. Does the citric acid act as a preservative slowing down pyro oxidation, act to reduce excessive base fog, or both?
I’d appreciate any insight from those having experience with these two offerings, how they compare, recommendations. I’m interested in using my JOBO to process pyro.
-- Hyperfocal (firstname.lastname@example.org), May 29, 2002
MOST of the effect of the revved up Pyro formulae is because of increase in the amount of developing agents and positive ph buffer. If you do the math you'll find the rollo is stronger by about 1/2 or 2/3's in it's ratios to the H2O. So it simply gets the job done quicker, ie. your silver build up is accomplished in 7 minutes instead of 12 and I assume by getting things done faster the film base plus fog just hasn't had an equal relative time to build up. This is probably way oversimplified but the idea I believe is sound.
I use the Rollo formula that was published in a View Camera magazine article by Carl Weese I believe. No matter what I do though, I get an edge spur on the reverse side of the film (ie. stain, not silver) caused by the little film edge lock that's built into my Jobo 2500 series 4X5 film support. After a lot of head banging on walls I finally resigned myself to sacrificing between 1/8 and 1/4" of film along the edges. For a long time I was blaming my film holders until a friend of mine pointed out that it's the tank that does it, not the holders.
Estar based films like aerial Pan X do better in the PMK formula because the Estar takes little or no stain anyway. With Ilford films I get a pleasing amount of stain in the Rollo or ABC+ or whatever it is.
-- Jim Galli (email@example.com), May 29, 2002.
Some additional info. I have been running ABC pyro in a 3010 drum at 7 minutes FP4, so the time is already relatively short. HP5 runs 9 minutes in twice the concentration of soup (1:2:50) and does have significantly more stain than the FP4.
I called B&S and got the formula, which has citric acid in solution A, instead of the EDTA stuff PF brand has. They really couldn't tell me too much about the differences between the two companies formulas. So I guess the citric acid must be added only to prevent early developer exhaustion (just like the EDTA).
-- Hyperfocal (firstname.lastname@example.org), May 29, 2002.
It's ascorbic acid NOT citric that's added to ABC+.
-- Linas Kudzma (email@example.com), May 29, 2002.
You might also consider using Pyrocat-HD in your JOBO, as it does not have the problem of generating too much stain. There are two pages on my site about Pyrocat: Testing Pyrocat-HD and Pyrocat- HD Film Developer.
-- Ed Buffaloe (firstname.lastname@example.org), May 30, 2002.