How To Make Gun Powder The Old Fashioned Way in Less Than 30 Minutes
Use a knife to drop out the puck, compress in plastic sheeting under the weight of a truck, or something similar, break the puck into 1″ or so chunks, and then let dry, warm in the sun, to keep KNO3 from forming large crystals. When nearly dry, tap to break further, and sift through mesh 20 WPI to 30 WPI.