Proportions by weight are 75% potassium nitrate (known as saltpeter or saltpetre), 15% softwood charcoal (willow is the best), and 10% sulfur.
spectracide stump remover for the potassium nitrate. sulfur from garden supply or ebay. charcoal is easy to make with a gallon can retort.
fill gallon can with sticks , best is willow. punch hole, or drill 3/8 hole in lid of can. set can hole down on fire with fire surrounding the can. gasses will soon vent out the bottom and burn off sounding like a jet. when gasses cease you have carbonize the willow. grind to a fine powder.
mix with potassium nitrate and sulfur proportionately and put in a ball mixer with the balls already in the mill for 24 hours. the loner it mills the faster it is. you can tell when its done by all the balls will be on top with the powder packed in the bottom.
when mixed blend with 91% isopropyl alcohol mixed 50/50 with distilled water, a small amount at a time until it is like clay, it will start to clean the sides of the bowl,
compress into pucks about 1.25 inches around and 3 inches long. scrape puck gently over window screen to create grains.harder pressure creates larger grains.
this part you just have to get the feel for how much pressure you need for grain size.
even if you get grain size to large(too much pressure) you can always reform it into pucks.
some people use 1 % dextrine as a hardener and binder but i think it makes more fouling.
let grains dry in a preferably controlled space with low humidity . some people dry it on plastic or matal pans so the potassium nitrate won't wick out into paper.. find some screens of different size to sift dry powder if you want to really control grain size.
try to avoid using metal in the process. grin
i have been to Dupont's old factory on the Brandywine. signs of explosions are still evident. laugh
there are several videos on youtube on making BP. one especially good is by a good old southern boy making it out side.
be safe and if you do make it make small batches. your spouse may want the house in one piece. grin
Last edited by deerstalker; 10/07/21.
