Paul, it's good to hear from you again! As a reminder, you and I independently discovered that s. metaborate dissolves in propylene glycol. But you discovered it a few years ahead of me.
Originally Posted by Paul Verizzo
Anyway, as I understand it, one reason for the fine grain of color developers is dye-clouds. Each little silver-grain is surrounded by a larger cloud of dye, so the grain does not need to be developed as much. That lower development means finer grain. But B&W films don't contain color-couplers, so they will need more development than C-41 to make grains larger, so grain probably won't be as fine. But I encourage you to try it and prove me wrong. I'm not joking! I'm surprised at how often I get surprised by developers.