Make Black Powder the Easy Way
IntroductionAt some point fairly early in every pyro career we realize we need to be able to make good black powder (BP) from scratch. BP is used in aerial fireworks shells as lift and burst powder. It is also used, in one way or another, in almost every other pyrotechnic device and component--mines, stars, black match, and the list goes on.
Black Powder Used as Aerial-Shell Lift Powder
Sources of commercially manufactured BP are becoming harder and harder to find. Most sporting-goods stores and gun shops have stopped carrying real black powder. Instead they deal in BP substitutes such as Pyrodex® and Hodgdon Triple-Seven®. These products won't work as shell lift powder. And even when real commercial black powder is available, it is relatively expensive.
So, availability and expense are the primary motivators to develop an ability to make your own high quality black powder. Add to this the desire that lurks in the heart of every pyro to "do it yourself" rather than rely on commercial sources, and it is downright irresistible.
The purpose of this project is to demonstrate a simple technique by which anyone with access to a few tools and the appropriate chemicals can easily produce high-quality granulated black powder. For use as lift and burst in aerial shells, and for many other uses, BP produced by this method is as good as or better than the commercial product.
Make Black Powder the Easy WayGood quality granulated black powder simply is that powder which suits our needs in our fireworking hobby. The primary requirements are performance (power) and durability (hard enough grains) that compare favorably with commercial granulated black powder.
There are many ways to make black powder, and the project "Making and Testing High Powered Black Powder" has an overview of some of them. You'll also find there a method to test black powder and compare it to certain standards.
But, we'll be focusing on a simple, easy way to make high-quality BP that is not mentioned in that project. The method we are about to explore does not require exotic chemicals. It can produce excellent BP using the most readily available, commercial airfloat charcoal made from hardwoods. It also uses the simplest of the available binders, dextrin, and the cheapest and safest solvent of all, hot water.
Ball-Milling Black PowderThe one, critical machine which makes this method of manufacturing black powder possible is the ball mill. The Quick & Easy Black Powder Ball Mill project presents an overview of a good, small, economical ball mill and provides important directions and safety information for its correct use. The directions below are tailored to the use of the mill described in that project, though if you already have a different mill, the instructions may be easily adapted.
However, if you
- do not already have a ball mill, or
- if you have the ball mill pictured below but have not yet properly configured it, or
- if you have not yet learned how to use your ball mill, then
Ball Mill from Skylighter (#TL5005)
It is the ball-milling which will give our powder the power we need. Ball-milling the black powder ingredients ensures a very small, fine particle size. This maximizes the surface area of the ingredients, and the resulting burn speed. After milling, the ingredients are also extremely intimately mixed. This is also necessary to maximize the speed and power of the BP.
The batch of black powder we are about to discuss is scaled to the size of this small ball mill. But, of course, the batch can be scaled up for use in a larger mill if one is available.
Black Powder FormulaThe most common BP formula is "75/15/10," which means 75% potassium nitrate, 15% charcoal and 10% sulfur. This formula has been known for centuries as one which will produce powerful black powder.
Note: This formula is also referred to as "15/3/2," or 15 parts potassium nitrate, 3 parts charcoal, and 2 parts sulfur, which amounts to the same thing.
In order to give our granulated powder the desired durability, we will be adding 1% dextrin to that formula. This will serve to bind the BP into hard, durable grains once it has been activated by hot water. With good ball-milling, 1% dextrin should produce BP granules that are very hard when they are completely dry. If even harder granules are desired, the dextrin can be increased to 2% without significantly affecting the final power of the BP.
The batch we'll be working with, then, for use in the ball mill from Skylighter (above), is as follows. The weights have been rounded off for ease of use.
Black Powder Formula
|Component||Percent||Factor||4.35 oz||127 g|
|Potassium nitrate||75%||0.75||3.2 oz||94 g|
|Charcoal, airfloat||15%||0.15||0.65 oz||19 g|
|Sulfur||10%||0.10||0.45 oz||12.5 g|
|Dextrin||+1%||+0.01||0.05 oz||1.5 g|
This size batch will fill one of the empty Skylighter ball mill jars about 1/4 full, which is the optimum material load to be milled.
Note: These amounts can be multiplied by 5 for use in larger, one-gallon ball mill jars if you have a mill that size.
Weighing the ChemicalsEach chemical should be dry, clean, and able to pass through a 20 or 40-mesh screen. Dry chemicals will be less likely to clump in the ball mill. Clean chemicals will not spark in the ball mill, and chemicals from reputable suppliers will be clean. Finer grained chemicals will grind more easily and quickly in the ball mill. If, for example, your potassium nitrate is badly caked and "chunky," work it through a screen first to make it easier to mill.
Weigh each chemical out according to the table above into its own separate container. Combine all of the weighed chemicals in a larger tub and weigh that as well to double-check that the weight equals the desired total. This verifies that the original weight of each chemical was correct.
Weighing Chemicals for a Batch of Black Powder
Add the chemicals to a ball mill jar loaded half-full of media, and close the jar securely. Set the mill timer for the desired mill-run time, which in this case should be 4 hours.
Ball Milling the Batch of Black Powder
Note: After milling, granulating, drying and testing black powder that was milled for 4 hours, you can try shorter mill-run times to see how that affects the power of the BP. You might very well get satisfactory results with 3 or even 2 hours of milling. That will depend on your chemicals, your ball mill, and whether or not you used the optimum milling method.
With the ball mill in a remote, safe, and adequately barricaded location, start the mill and let it run until the timer turns it off. It is relatively safe to be next to the mill when it is started, since its jar only contains unmixed chemicals at that point. But, as the mill runs the chemicals are mixed and ground into an explosive composition. Once started, until the timer stops the mill, no one should be in its vicinity.
Removing Ball-Milled Black Powder "Mill Dust" from the Ball MillOnce the raw individual chemicals have been milled together and before further processing, the black powder is commonly referred to as "mill dust." Mill dust is an extremely flammable explosive.
It is now time to separate the mill dust from the ball mill media. Do this operation outdoors, observing all the safety precautions.
- Perform the next steps outdoors. Minimize dust, and eliminate any potential sources of ignition from the area.
- Wear safety glasses and cotton clothing (long sleeves, and long pants). (Synthetics will melt onto your body in a fire.)
- Wear rubber or nitrile gloves, and a dust mask.
- Keep a 5-gallon bucket of cold water nearby, into which a burn can immediately be immersed.
- Minimize exposed composition and devices to only what you are currently working with.
- Keep any mill dust, or completed black powder, tightly covered and in safe storage.
Carefully open the ball mill jar and gently pour its contents into the screen. Tap the jar and its lid with something non-sparking (for example, an aluminum or wood rod) to remove any excess mill dust and get it into the colander.
Gently slide the media back and forth in the screen until all the mill dust has sifted down into the bucket, leaving only the media in the screen.
Gently pour the media back in the mill jar and cap it.
Tap the screen to get any remaining dust to drop into the bucket.
Put a lid on the bucket until moving on to the next steps.
Removing Mill Dust from Mill Jar and Separating It from the Media
Wet Granulating the Black PowderAs it is right out of the ball mill, the mill dust will burn very rapidly with a "whoosh" if a small amount of it is lit with a fuse. To test this, lay out a short, 1/4-inch wide line of the mill dust on a suitable outdoor surface. Be sure your larger container of mill dust is a long distance away from the line of powder. Put one end of a 3-inch (at least) piece of visco safety fuse in the end of the line of mill dust, and ignite the other end.
Note: Many a budding pyro has been tempted to perform this test using a "pile" --or worse yet a "PILE"--of powder. Many of these same budding pyros have ended up with painful burns. Such pyros tend to become discouraged and make poor Skylighter customers. A modest "line" of powder as described above is a far safer way to test your compositions, and far less likely to surprise you unpleasantly.
Many pyrotechnic projects call for "Meal-D" grade black powder. Some examples of these are formulas for the manufacture of stars and some other formulations, manufacture of BP-coated rice hulls for burst, priming of stars, manufacture of black match, etc. Commercial Meal-D is the extremely fine powder which remains after the granulation process, called "corning," which is used in the commercial production of granulated black powder. We will be using a different granulation process here, but the mill dust you've made with your ball mill is suitable for use as-is in many applications calling for "Meal-D" grade black powder. In fact, although it can be a bit messy, such fine mill dust can even be rammed in rocket tubes to serve as a fuel in some types of rocket motors.
So, why don't we use it as-is for aerial shell lift and burst powder? The answer is that the fine mill dust will pack together into a relatively solid mass inside a shell casing or lift-cup. This relatively solid mass of powder will not allow flame to propagate through it rapidly, so it will burn relatively slowly and not very powerfully. Also, ball-milled fine mill dust is very messy to work with.
For these reasons, we use granulated BP for shell lift and break charges. Grains of powder will have a relatively high exposed surface area per volume, and their irregular shapes will allow flame to move rapidly through a quantity of them. The solid grains are also easy and clean to work with.
Recall that the mill dust has 1% dextrin in it to act as a binder. To granulate the mill dust, we will be adding very hot water to it to activate the dextrin binder. We will then create a ball of "putty," and granulate that putty "grating" it through a wire-mesh screen.
The screen we will be using to granulate the BP is a 4-mesh Skylighter screen, which has openings that measure approximately 1/4-inch square. So, our resulting granules will be about 1/4-inch and smaller in size. Smaller granules will burn faster and more powerfully, but it's difficult to nicely granulate BP through a screen much smaller than the 4-mesh one. If we want smaller granules, it'll be easy to break the large granules into smaller ones once the BP has been granulated and dried.
So, let's get started.
In a safe location, away from the pyro workshop, boil approximately a cup of water.
Put the mill dust into a small mixing tub, large enough to work in with gloved hands.
Bring the pot of water to the pyro area, and pour slightly less than two tablespoons of the hot water onto the mill dust. Work the water into the dust with gloved hands until a putty ball forms. The ball should glisten slightly after being handled with your gloved hands. It should be nice and stiff, like a dense ball of Play-Doh.
When dampening a composition like this, it is much easier to add more water if it is needed than it is to remove water if too much is added. Makes sense, no? So always start with a little less water than necessary, which the "slightly less than two tablespoons" should be. Then add a few drops of water at a time if necessary to achieve the nice ball-of-putty consistency.
Making a Glistening Putty-Ball of Black Powder
The Finished Product, Ready to Grate
Now, place a 4-mesh screen over a kraft-paper-lined tray. Using quite a bit of force and pushing down, grate the BP ball across the screen to create ribbons and granules which fall down through the screen onto the tray. Grate all the black powder this way through the screen.
Screen-Granulating Black Powder
Use a stiff bristle brush to clean any excess powder off the screen and onto the tray. Use a chopstick or coarse-toothed comb to break up any clumps of BP and spread the granules evenly on the tray.
Breaking Up Clumps of Granules
Put the tray in a warm, breezy location so the granules dry quickly. This quick drying is important for the production of powerful black powder. We want the BP to dry before the potassium nitrate has a chance to re-crystallize into larger crystals than the very fine ones the ball milling created.
A drying box, or even a food dehydrator where the heating element can be protected from any pyrotechnic compositions, can be ideal for drying such powders.
Re-screening Dry Black Powder Granules, and Separating the BP into "Grades"The dry black powder granules should now feel very hard and "crispy." Some of the granules will have glued themselves together after the wet screening. To break these up, we simply want to re-screen the granules through the 4-mesh screen again.
Remember that we are dealing with one of the more powerful pyrotechnic compositions--black powder. Observe all safety precautions:
- Keep all possible sources of ignition far away.
- Use only non-sparking implements.
- Minimize dust.
- Thoroughly clean up after yourself.
- Store all finished black powder in a sealed container, in safe storage.
Re-Screening Dry Granules through the 4-Mesh Screen
Once all the black powder granules have been worked through the screen, your black powder can now be referred to as "-4-mesh" (minus four mesh). That means all the granules will pass through that size screen.
There are some small granules which can be screened out of the black powder by sifting the BP gently through a 20-mesh screen, or a larger-opening 12-mesh screen colander.
If the powder is sifted in the 12-mesh screen, and the particles finer than the 12-mesh openings are removed and set aside for other uses, then the BP that remains in the screen would be referred to as "-4+12-mesh" (minus four, plus twelve mesh). This means that all the granules would pass through a 4-mesh screen, but would be retained on a 12-mesh screen.
That size range, -4+12, is the particle size range of grade 2FA commercial black powder.
Screening Out Fine Powder with a 12-Mesh Screen
As was stated earlier, fine granules burn faster and more powerfully than coarse granules. You may wish to convert some or all your BP to the finer mesh sizes that grade 4FA commercial powder contains.
In that case, put your granulated BP in a sealed plastic baggie. Gently roll across the enclosed powder with a wood dowel or aluminum rod to break up (but not pulverize) the large granules.
Re-screen the granules until they all pass the 12-mesh screen, but are retained on the 20-mesh screen. This results in "-12+20-mesh" granules, which is the same range of particle sizes found in grade 4FA commercial BP.
Making Finer 4FA Black Powder Grains
The still finer powder which passes through the 20-mesh screen can be used for priming stars or comets, for other purposes. It can also be retained and incorporated into your next batch of black powder putty, to be converted into larger grains.
Testing Your Homemade Black PowderIt is a good idea to test your black powder's power to verify that it suits your intended uses. One good test is firing baseballs from a 3-inch mortar and timing the flight of the ball from launch to landing. For a complete overview of this type of testing, see Making & Testing High-Powered Black Powder.
3/4-ounce of good commercial grade 2FA black powder will result in baseball flight times of between 6 and 9 seconds. BP of that power will serve very well as lift powder for aerial shells.
The particular batch of black powder shown being made in this project's videos, using commercial airfloat charcoal, produced these test results:
- 3/4-ounce 4FA-granulation BP, 8-second flights
- 3/4-ounce 2FA-granulation BP, 6.5-second flights
Testing Black Powder by Firing Baseballs
"Fast Ball, 200-MPH!"
Based on these test results, the granulated black powder we just made using this simple and easy process would serve well as aerial shell lift or burst powder.