Began using PMK "pyro" developers soon after the publication of Gordon Hutchings book on Pyro developers in the later 1990's. Initially used PMK with 4x5 nikkor tank. This often produced uneven pyro stains on the negative and very uneven stains specially along the center spiral support of the Nikkor reel. Gave up on using the 4x5 nikkor tank with pyro developers.
Ended up using the 5x7 Jobo expert drum back filled with nitrogen with modest rotation speeds. This combo resulted in the most even pyro staining on the negative. It is possible the ribbing in side these tanks cause uneven fluid flow across the negative or pyro developer stagnation in specific areas which results in uneven pyro staining on the negative. Pyro developers depend on essentially even distribution and developer action across the negative during the development process to achieve uniform staining over the entire negative area.
Bernice
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