Pyro in Unicolor : LUSENET : Large format photography : One Thread

Just got a Unicolor machine and I like the results I get with Rodinal 1:50 for developing 8x10 Tri-x. But when I tried my preferred developer, Pyro PMK, the negative was terribly thin, even though I increased development time by about a third. What to do?

-- Bruce Schultz (, April 04, 2002


Basically, pyro oxidizes too rapidly with constant agitation, and therefore, it doesn't matter if you increase the development because the developer is shot. How much solution are you using? If 250ml or less, then try 500ml and see if that corrects it. If not, you'll have to try one of the other popular solutions: 1)Add EDTA (Calgon); 2)Double the "A" portion of your developer; 3)Double A & B ; 4)Dump the developer midway though the cycle and add fresh solution. You'll have to experiment to find what works for you. If I recall, from "The Book of PYRO," Hutchings advises doubling A as a first step.

If all else fails, you can try Rollo Pyro (a formula somewhat like PMK that uses considerably more pyro). Also, you might want to consider a catechol based developer like Pyrocat-HD. See Ed Buffalo's site,, for the formula.

-- Ted Kaufman (, April 04, 2002.


I use a JOBO rotary processor with Pyro and get very good results. If you use Hutchings PMK it will oxidize too fast. You need to modify the formulation as was previously suggested, or use Rollo Pyro or ABC+ Pyro, which use EDTA as a preservative.


-- Pete Caluori (, April 04, 2002.


I use Unicolor 8x10 and 16x20 print drums and a Unicolor reversing roller base to develop 8x10 and 8x20 sheet film. Rollo Pyro works fine, but I like Pyrocat-HD even better. Pyrocat has never given me streaks or any problems sometimes associated with staining developers and film in print drums.

-- Linas Kudzma (, April 04, 2002.

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