How can 4F not absorb moisture more quickly than coarser powders since its surface area:volume ratio is so much greater? After all, that's the very reason it lights faster.
Because good powder does not suck up excess water from the air.
Its a CHEMICAL thing.
Put a small amount in a shallow pan or saucer.
Use one for each granulation.
Put in a place like a covered porch where no LIQUID water, rain, dew etc can get at the powder.
Leave overnight when the humidity is high.
Did the FFFF liquify?
If the powder passes this test then it should be OK in a FL pan that is KEPT DRY and is CLEAN.
Believe it or not we have high humidity in MT.
Like when hunting is a creek bottom with thick brush covered with wet snow temp about 33-38f.
I stalked through this:
For about 45 minutes, shot 2 deer and only used my hand the keep wet off the pan, no time for a cover of any kind. I think I reprimed once when some snow got on the barrel behind the rear sight and instantly turned to water. This with Swiss Null B which is finer than FFFF but is still a polished powder, but no graphite, just polished during the final drying process.
I did finally get the lock wet while collecting the deer. But my tags were both used and the Blackfeet no longer bother people in Southern MT and besides I had a FL pistol
I still feel that if the FFFF is turning to goo there is problem with the powder or moisture is condensing on the metal somehow.
Do the open pan test.
If the stuff sucks up moisture to that extent then why does it still flow from a horn?
Dan