This receipe has been taken from an article by Rev. Dr. J.D. Hooker in a magazine called the Backwoodsmen. The editors note is Niether the author or this magazine take any responsibility for the making of black powder. It is presented for informational purposes only and their suggestion is to buy your black powder.
2 buckets, 1 large and one slightly smaller,
Holes in the bottom of the bigger bucket.
2 heavy cloths, large enough to cover the bottom of the big bucket.
Clean sifted white wood ash enough to cover the bottom of the top bucket.
1 cup of sugar.
2 tablespoons full of fine red rust.
Piece of wire window screen
Prepared dirt (from a chicken coop, horse corral, barn where farm animals are kept)
Place heavy cloth on the bottom of the bucket with holes
Add the wood ash and spread evenly on the cloth
Place the 2nd piece of cloth over the ash
Fill the rest of the bucket to within 2 inches from the top with prepared dirt
place the filled bucket over the smaller bucket
Gently sprinkle the 1-1/2 gallons of boiling water over the soil
Leave set to drain for a couple of hours
Remove the top bucket when drained
Bring the lower bucket to a boil and keep simmering
Tiny grains of salt will form as the liquid simmers
Dip these salts out with a wooden spoon and discard
After 2/3rds of the liqiud simmers away set aside to cool for an hour or two
Strain out the the saltpeter crystals and set aside to dry
Put 2 cups of water into a pot and bring to a low boil
Add 1 cup plus 2 tablespoons of the home leached saltpeter to the water
Add 1 cup of sugar
Add 2 tablespoons of fine red rust
Stirring constantly, keep simmering until it becomes just a little thicker then regular breakfest oatmeal
Spread out about 1/4 inch thick on a cookie sheet
Cut 1 inch squares and set to dry
About every 15 minutes cut the pieces smaller
Once dried out enough that it no longer sticks to your fingers, take about a tablespoonful and carefully rub it through a piece of wire window screen.
Set out and let dry until dead bone dust dry
Take about a third and crush with a mortar and pestle (not metal) for use as priming powder for flash pans
Makes about 1 pound of good quality gun powder loaded volume for volume as commercial black powder.
I have not tried this yet as the weather has been quite moist here in Oklahoma and have not the desire to try this indoors. But when the weather changes and becomes dryer I can give this a shot outdoors and then test the results. But this is the way it was done in the mountain country back east before commercial powder bacame available and affordable to them.