I finally collected some test-strips I'd developed over the last few weeks, and measured base+fog (B+F) levels for Phenidone at various pH-levels using TMY2. All test-strips were developed to approximately the same contrast as XTOL. Here's the graph:
Originally Posted by Gerald C Koch
The graph is jumpy and crude, partly because I changed pH-meters partway through. But it shows a trend: As pH rises, Phenidone's B+F rises. For comparison, XTOL uses Dimezone-S, and its B+F is .25 at pH 8.3 (with TMY2). Phenidone only gets close to XTOL's level when pH is no more than around 8.10.
Caveat: All of the Phenidone developers in that graph use ascorbic acid and sodium metaborate. Other chemistries might cause Phenidone to behave differently.