Well, it seems to be metol and something. Not glycin, not phenidone. Looks, acts, and smells like metol. It's very gentle, and pleasantly sharp. No idea what pixie dust Crawley added. A fine developer. FX2, in Crawley's original version and Troops variation ( Formulary ) are exquisite, too.
The sole drawback to FX39 is that once the bottle opened it goes bad quickly.
FX2 / TFX2 lasts a long time ( separate solutions ). That might decide the case for a Jobo.
FX1 is a remarkably good developer, but tends to build density in the highlights. I rely on reduced agitation to balance this: in a Jobo, I'd bet you'd have a problem with this.
FX2 will drive PMK out of your memory.
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