I can pretty much tell by looking at the stuff. I would dump it out, and by basically shifting the powder about, get the fines out. Use them for priming, or if you don't want them for that, do it outside and just blow them away . [ light breeze works ] It is the fines [dust ] that raises the pressure but, if you don'thave that much of this stuff..........is it worth the trouble ? Are you sure it is all true black powder ?