Making Black Powder with a Ball Mill
You can get potassium nitrate for making black powder really cheap, if you can find prilled or hard nitrate. "Prilled" nitrate comes in little spheres, around 1 mm or less in diameter.
Make Black Powder Using Cheap Potassium Nitrate Prills
How to Make Black Powder Using Coarse Chemicals
Prilled nitrate is too coarse to use as-is in making black powder and other fireworks, but once you grind it up to about 200 mesh, it's perfect.
Keep in mind that potassium nitrate, like most oxidizers commonly used in making fireworks, eventually absorbs enough water to get more or less petrified. But it's still good. You just need to grind it up into a fine, fluffy powder again. It never goes bad, even if it's gotten wet or has been stored for years.
So learning to grind/mill hard chemicals is one of the routine tasks that all fireworkers need to master.
We routinely recommend two ways: coffee milling and ball milling. Both ways have advantages.
To grind a single chemical (vs. a mix like black powder) using a ball mill, fill your mill jar half full of hardened lead or brass grinding media, and 25% full of potassium nitrate. Turn the mill on and come back in an hour. Your nitrate should be light and fluffy. If not, continue grinding it 'til it's fine powder with no chunks or grains.
But guess what?
The good news is that sometimes you don't need to do anything extra like pre-milling. Here's a quick and dirty video I made. It shows how you can even use coarse chemicals and primitive equipment to make black powder just as good as any commercially made BP.
Making Black Powder with a Ball Mill
Just so you know what's going on. This is me in my backyard. I am using a homemade ball mill I've had for 20 years, and Skylighter's 1/2" antimony-hardened lead balls.
Check out my fancy-dancy mill jar! It's a one-gallon plastic mayonnaise jar stuck inside a large coffee can for reinforcement. I actually have to tape the screw top on it so it doesn't come off while it's turning!
This is down and dirty, almost totally homemade equipment. You do NOT need to be fancy or sophisticated (which I sure as hell ain't!) to make great black powder which performs as well as anything you can buy.
To make this black powder, I'm using Skylighter's el cheapo, prilled potassium nitrate–the cheapest stuff we have. Everything you see is right out of the containers—no pre-grinding or screening. The point is, look at how quick and easy it is to make black powder using really coarse potassium nitrate without having to spend any time making it finer first.
When the black powder's finished, you'll see me using my busted up old bucket screen to separate the lead balls from the new black powder. (You will NOT be impressed!)
Remember these magic proportions when you're making black powder with a ball mill:
- Fill your mill jar half full of hardened lead balls (or brass)
- Fill half of the remaining space with your 3 chemicals
- Leave 25% empty "head space"
Got it? 50% lead balls, 25% chemicals, 25% air.
These proportions are the "sweet spot" that guarantees that your powder will be good AND that you can do it in the shortest amount of time (typically 3-4 hours).
Troubleshooting: How to Prevent Pitiful Powder Syndrome
From time to time, folks call who have been seriously afflicted with Pitiful Powder Syndrome, an acute black powder deficiency known to cause all manner of fireworks failures and hair-pulling.
Their symptoms are always the same: their ball-milled black powder doesn't work.
So, the first thing we do is get him (the "hers" are never afflicted) to describe how he made it.
Every time... I mean every single time, the victim's PPS can be traced to making the black powder a different way than the simple process shown. (Or, as we were warned in kindergarten, by not following instructions—a manly trait.)
Here's how people most commonly get infected by Pitiful Powder Syndrome:
Not using enough milling media: Always fill your jar 50% full of grinding media.
Using media that's too small: Use 1/2" for 1 gallon mill jars or smaller; 3/4" for larger mill jars; for 5 gallons or larger, use 1-inch.
Using lightweight grinding media: You want lead or brass. Both are heavy enough, but will not spark or cause an accidental ignition. Do not use steel or ceramic. They can cause another syndrome—death.
Milling for too short a time: run your mill for at least 3 hours. You probably don't need to run it longer than 5 hours. Milling longer than that will probably not improve your black powder significantly.
Using different chemicals: Standard black powder is made with potassium nitrate, sulfur, and charcoal. Switching or omitting chemicals is a common cause of pitiful powder. Do not waste time and money by second guessing these chemicals.
Remember: making black powder this way is a tried and tested method, perfected for hundreds of years by people who learned more about it than you and I ever will.