One thing that's counter-intuitive:
I just cleaned out & restarted my stove a day ago.....Normally I get fine, powdery ash for a few days after starting a new fire & running it at low temps. (coal bed settles nicely, all by itself)
Now that I am running the stove fairly hot, I find the same nice Blaschak coal bridging like crazy & stuck together badly, needing to be poked like an "old" fire??
I would have thought that the hotter the fire, the more powdery the ash, but it's just the opposite! (I wonder why??)