Desertbuck, if you have a copy of VanMaltitz's book, Blackpowder Manufacturing, Testing & Optimizing, he describes a precipitation method used by the Chinese over a thousand years ago - no alcohol, just enough boiling water water to dissolve the KNO3 - as the "soup" cools down to room temperature, within seconds it turns into a sludge (eg, ketchup consistency). No need to squeeze the water out, just let the sludge dry.