I have always wanted to try this, and this was my opportunity. My grandfather taught me how to make this, but I was never allowed to. Gunpowder is cheap, easy, and also surprisingly fun to make. DISCLAIMER: I am not responsible for any injuries, damages, or deaths caused by this instructable.
Now lets get started!
Step 1: Materials
Some things you'll need are:
• potassium nitrate (stump remover)
• mortar and pestle
• spoon (plastic to avoid too much friction)
• coffee filters (4-5)
• scale that measures grams
Step 2: Grind
Charcoal sulfur and potassium nitrate need to be ground to a very fine powder separately. This is very important in order to get it to ignite. Separate the ingredients into the coffee filters and then get the scale ready.
Step 3: Weighing and Mixing
Now weigh out 7.5 grams of charcoal, 3 grams of potassium nitrate, and 1.5 grams of sulfur. Experimentation is required here.
To mix, place all ingredients into mortar and pestle and blend gently until thouroghly mixed. P.S. you might try putting the gunpowder in a plastic bag and squeezing the bag over and over, or you may put it in a plastic cup and stirring it with a plastic spoon.
Step 4: Finally...
Now it is a flammable dangerous pyrotechnic compound, so be careful and have fun!