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Home Manufacture of Black Powder by Don WIlliams

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Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press

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I am compelled to add a few words of caution and disclaimer to this brief explanation. Remember that the manufacture of black powders is a regulated activity in many areas. One should do some research into the legal requirements before attempting to do any of these steps. The procedures described represent my own experience and are not necessarily recommended as the final word in how to do it properly and safely. These explanations are made available to others in order to stimulate constructive dialog for enhancement or improvement.

Without black powder in all its varieties, it would be tough to make much more than sparklers for pyrotechnical displays. Making high performing black powder is one of the fundamental skills that the aspiring pyrotechnician will probably want to master early in his quest for knowledge in the field. The goal of this meager treatise is to illustrate the most popular method of amateur production which is called the "ball milling method." This implies that anyone who wants to use this approach will need to first build or have access to an efficient ball mill . Without a mill, one is left with the inferior alternatives of using the CIA (precipitation) method or the incredibly laborious mortar and pestle method.

The first step in the process is to assemble the raw materials. In this case, there are only three, as pictured: potassium nitrate, charcoal and sulfur. Of these three, potassium nitrate and sulfur can readily be purchased from pyro supply companies such as Skylighter or AMERICAN PYROTECHNIC SUPPLY, but charcoal is a different story. The subject of charcoal could require a whole book to adequately cover. For the purpose of brevity, this text will assume that willow charcoal is one of the most popular choices for making high performance black powder. Unfortunately, commercial sources (at least in the US) for this particular kind of charcoal are very rare. The best approach is to make it yourself with a home-made charcoal cooker. Then you can control some of the characteristics of your charcoal by custom cooking it to your liking. .
If you make your own charcoal, you need to reduce it from the original sticks to a more usable powder form. I use the meat grinder method shown here. A guide chute has been fashioned from a sheet of transparency film to help keep the dust down. This is definitely not a job to do in your kitchen unless you want to risk sleeping in the garage for a month. A good respirator is also recommended. The result is a charcoal powder which ranges from air float to about -8 mesh. This may or may not be useful "as is" for making black powder, depending upon the approach used to make the green meal. Hopefully, this will become clear in a moment.
Regardless of the method used to make the green meal, the proper proportions can only be achieved by weighing them on a scale. I generally use the traditional ratio of 75 parts potassium nitrate, 15 parts charcoal and 10 parts sulfur. If your black powder is intended primarily for use as lift powder, you might want to use the ratio which is purported to be optimized for this purpose. It is 74 parts potassium nitrate, 14 parts charcoal and 12 parts sulfur. Just remember that these are parts by weight. It seems that every "newbie" to pyrotechnics will reveal his ignorance by asking the question concerning whether parts in a formula refers to weight or volume. Save yourself the embarrassment and etch upon your mind that pyro formulas are always in parts by weight unless specifically stated otherwise. The triple-beam balance scale shown does the trick quite nicely for weighing out parts of a formulation, but you can accomplish the same purpose with a much less expensive home-made scale .
Let's diverge to a little background discussion for a minute. The green meal referenced above is the raw, unprocessed mixture of the constituent ingredients. There are two basic approaches to creating this initial mixture. One method is to create a bulk mixture from which a "volume measured" portion is taken and placed in the milling jar. The other approach is to create a batch of green mix which is exactly the amount needed for the intended milling jar charge. In the first case, the particle size of the individual components of the mix must be small enough to assure homogeneity. In the second case, there is no concern about the green meal being homogeneous. The potassium nitrate and sulfur can be full of lumps and the charcoal can be very coarse. The proper weight portions are just loaded into the mill jar and the milling accomplishes the homogeneity. The second approach has many advantages, but it can only be done if the user knows the exact weight of the optimum charge for his milling jar. For the purposes of this discussion, the definition of an optimum charge is the following: the amount of fully milled black powder meal which occupies 25% of the mill jar volume. The determination of this optimum charge is challenging because milling will often alter the volume of that which is milled. The best way to determine the weight of the optimum charge is to actually weigh the desired volume of finished meal. This implies that the user of a new milling jar must use the first approach to making green meal for his first batch. The optimum charge is then determined and can be used for all succeeding batches.
The first approach to making green meal will be demonstrated because it also includes many principles of properly mixing pyrotechnic chemicals. In general, successful pyrotechnic compositions work well because their proportions of ingredients have been very carefully determined. If the pyro-technician allows the proportions of his mixture to vary from the ideal, the performance of the composition will usually suffer. Therefore, except in a few unusual cases, a high degree of homogeneity is desired in pyrotechnic mixes. One of the best ways to accomplish this is by using screening (which requires a good set of mixing screens ) as a means of mixing pyro chemicals together. In the picture at the left, is shown the results of screening a mixture of the potassium nitrate and sulfur which were weighed out for the bulk black powder green mix. The two chemicals were stirred together and appeared well mixed. However, upon passing the mixture through a 40 mesh screen, many large lumps of sulfur are revealed. These lumps obviously destroy the homogeneity of the mix in their near vicinity.
In order to eliminate these lumps, I perform a rough approximation to a mortar and pestle operation by placing the lumps in a container. The lumps are crushed by the back of a spoon against the sides of the container. The contents of the container are then returned to the mixing screen box and the cycle is repeated until all of the material passes through the screen. The entire quantity of mix is then passed through the screen several more times to ensure a thorough mixture. This method works well if the lumps aren't hard and dense. If they are too hard to crush easily, the best way to eliminate them is by milling each chemical separately prior to mixing with others. Now, to complete the black powder green mix, the charcoal must be added. The screening method could have been used to mix all three chemicals together in one step, but I prefer to add the charcoal as an "airfloat" which will be free of coarse particles. The charcoal is added to a container with the screened potassium nitrate and sulfur, a tight lid is used to close the container and the container is shaken vigorously. I do this because screening any mix which contains fine charcoal will usually result in a lot of airborne dust which enters the lungs and coats the pyro lab with a nasty black film. At this point, a black powder green meal with a reasonable degree of homogeneity has been achieved.
Now a volume of green meal equal to 25% of the mill jar volume is measured. For this jar, that volume is 3 and 1/4 cups of our bulk green meal. This is the first approximation to the theoretically ideal mill jar charge. It is added to the jar along with hardened lead milling media equal to 1/2 of the mill jar volume. In my experience, the volume of the black powder meal will increase during the milling. If you have a high efficiency mill, the milling process will be complete in about 3 hours of milling time. I would be remiss if I didn't mention that the milling should be done with all the due precautions taken. This means locating the mill remotely and perhaps using protective barriers around it.
The powder which results from the milling process is still referred to as "meal" because it is not yet very useful for pyrotechnic applications. However, it is no longer called green meal. The meal is processed into grains of black powder by a method known as corning. The size and characteristics of these grains will determine some of the aspects of the performance of the finished black powder. The first step in the corning procedure is accomplished by using a powder die to compress the milled powder into "press cake". One of the secrets of making durable black powder grains is to add sufficient moisture to the meal prior to pressing it into the cake. I add 4 grams of 50% water/50% alcohol to 119 grams of milled meal to make an individual die batch. This is done by placing the meal and water/alcohol in a mixing cup and stirring vigorously with a stirring rod. The milled powder will undergo a fairly rapid transition from fluffy, loose powder to a stiff, but still crumbly powder when the moisture becomes well distributed. Some will advocate adding moisture by misting it lightly onto a pile of milled powder while mixing with the diapering method. Theoretically, this avoids degrading the performance of the powder by not giving the potassium nitrate a chance to dissolve and recrystallize. However, I have found this trouble to be unnecessary. The picture shows the dampened, milled powder being added to the powder die, after which the compression piston is placed on top.
Next, the die is placed in a home-made hydraulic press and the press is operated from behind the blast shield. This picture is illustrative of the pressing step, but in actual operation I recommend the use of a heavy glove on the hand which is used to pump the hydraulic jack. This and a heavy sleeved shirt or coat are a good idea. The die has been designed so that the finished press cake has the desired density of 1.7 grams/cc.
These are the puck shaped pieces of press cake which are extracted from the powder die after pressing has been completed. They are rock hard and should hold together well without crumbling. If the press cake crumbles easily, this is one indication that insufficient moisture was added to the milled powder. The press cake pucks are allowed to air dry for at least 24 hours before they are crushed into powder grains. Tapping on the pucks with a wooden dowel makes a china-like clinking noise even right from the powder die. After drying for a day or so, the pucks will ring even a little more, indicating that the moisture level is about right for the final step of the corning procedure.
Crushing the press cake into useful grains is somewhat nerve-wracking for me, but I like this step because it is the last in a long series required to finally obtain high performance black powder. I use a small baseball bat to crush about 1/2 of a press cake puck at a time. The chunk of press cake is placed in an old aluminum pressure cooker pan and the bat is used in short, downward strokes to break up the cake. This works best if the pan is placed on a very hard surface, such as concrete or stone. The idea is to fracture the cake into grains without crushing it back into useless powder. Again, for safety's sake, this should be done outdoors with protective clothing and always avoid placing your face directly over the pan. If 60 grams of black powder were to ignite in the pan, it would create a hot flame as much as 4 feet high before your reaction time would allow you to get out of the way. As I said, this step is a little nerve-wracking, but I have never had an accident during this step yet. There may be some arguments for using a plastic bucket instead of an aluminum pan, but I'll leave this choice open to discussion.
The contents of the crushing pan are emptied into a stack of screens to separate the various desired grain sizes. Whatever will not pass through the top screen is returned to the pan for more crushing with the "bat pestle" and this cycle is repeated until all the black powder cake passes through the first screen. A little side to side shaking of the screen stack during each cycle helps the grains settle to their proper location in the stack. This particular stack of screen boxes consists of the catch box, a 40 mesh, a 20 mesh, a 10 mesh and a 4 mesh screen on top. The powder which falls clear to the catch pan is a -40 mesh powder which is retained for use whenever meal D is called for in my pyro formulas. The powder in the 40 mesh box is a 20 to 40 mesh powder which is used as 4FA equivalent. The powder in the 20 mesh box is a 10 to 20 mesh powder which is used as 3FA equivalent. Finally, the powder in the 10 mesh box is a 4 to 10 mesh powder which is used as 2FA equivalent.
This picture is shown to give an idea of the various grain sizes relative to common US coins. Now I'd like to explain a little about my philosophy regarding my choice of screens for separating the grains into these ranges. The ranges don't conform exactly to those given for the common commercially produced powders and this is intentional. The only motivation I can think of to conform more closely with the commercial definitions for black powders is to enable a completely transparent exchange of commercial and home-made powders in pyrotechnic projects. In these cases, the pyro craftsman wants his home-manufactured powders to perform identically to commercial powders so that he can always expect consistent end results. In my case, I don't use commercial powders. Therefore, I can afford the luxury of adjusting the amounts of powders used in my projects according to the desired results. This way, my only concern is to make my own manufacturing process very consistent so that my home-made powders always give me the same results. The advantage of this approach is that the ranges of grain sizes for my equivalent powders don't overlap as they do in the commercial ranges. This means that I can use commonly available screens and do multiple separations in one step as illustrated above.





A Ball Mill


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



I approached this project the patient way and started by first ordering the milling bible entitled "Ball Milling Theory and Practice for the Amateur Pyrotechnician" by Lloyd Sponenburgh. I have not faithfully followed his plan, nor do I expect you will follow mine. However, for those of you who are dying to build your mill without buying the book, this page illustrates the general approach.

I have pictured the entire mill here for visual reference as you look at the remaining illustrations.
First, you have to decide what kind of frame to mount your mill on. I simply made a rectangle with 2 X 4's and screwed two layers of 1/2 inch plywood on top.  Whatever you use, it must be very sturdy!! These mills must endure heavy vibration and weight loads.
The electric motor should be a 1/3 to 1/2 horsepower, capacitor-start, 1725 rpm, 115v motor. You can get one from Grainger using part # 6K758. In my case, I am using a motor salvaged from a washing machine for which I paid $10. Since it has coils for 2 speeds, I used 2 switches. One switches between hi and low speed and the other is the on/off switch. It turned out that I only use the fast speed, so the speed switch is superfluous. The shaft sheave on the motor should be 2 inch o.d. by 1/2 inch (Grainger #3X895).
The drive shaft for the mill is 5/8 inch round steel bar stock. These can be purchased at any hardware store. Be sure it is perfectly straight. The sheave on the drive shaft is a 6 inch o.d. by 5/8 inch (Grainger #3X919). This cost me $3.72. You will also need two self-centering ball-bearing pillow-block bearings to mount the drive shaft (Grainger #2X898). I had to sand the drive shaft a little bit to allow the bearings to slide onto the shaft.
Before placing the bearings on the shaft, you need to place a piece of automotive heater hose on it as shown here. This hose is 5/8 inch i.d. by 7/8 inch o.d. It can be found at most hardware or auto parts stores. A little lubrication of some kind on the shaft will greatly aid the sliding on of the hose.
The other side of the mill jar cradle uses a ball bearing equipment roller. I bought this one at Woodworker's Warehouse for about $10. This picture shows the roller removed from its bracket. The roller has been covered with two layers of bicycle tire inner tube. The inner tube layers have been folded back in the picture for illustrative purposes only. You may be wondering how to get the inner tube layers over the roller. Again, Lloyd describes a technique which works very nicely.
Start with a 26 inch by 2 inch bicycle tire inner tube. Cut the deflated tube about 3 inches from the valve stem and tightly tie a cord around each end so the tube can be inflated to look like a long three inch diameter sausage. The trick is to push the roller end into the end of the inflated inner tube. When the roller is completely enclosed by the inner tube with a few inches of overlap, you can cut the sausage off near the valve stem to allow it to deflate. You now have two layers of rubber over the roller which are connected at one end. After allowing the rubber to relax a little bit, you can now trim the ends with scissors to within 1/4 inch of the ends of the roller. Now re-install the roller in its bracket and check for unimpeded rotation.
If you mount the drive shaft and equipment roller perfectly parallel, your mill jar may not creep as it rolls in the cradle. To be safe, I installed this bumper to prevent the mill jar from exiting its cradle. I used two Teflon furniture slides on the bumper to allow the mill jar to slide against the bumper with little friction. The drive shaft and equipment roller are mounted with 3 inches of space between them to accommodate both a 4 inch and 5 inch mill jar. A 6 inch mill jar requires a space of 4.5 inches.
This is a mill jar which has been constructed from 5 inch PVC pipe and fittings. The milling media is antimony hardened, 3/4 inch lead balls. The construction of the jars is relatively simple, but is a subject for another project page.
Finally, this shot shows the placement of the 5 inch mill jar in the cradle. With this setup, I can mill about 3 1/4 cups of high quality black powder in about 3 hours. The efficiency of this mill is dependent upon many factors which are explained in Lloyd's book. There is a wealth of information about milling theory contained in the book and I would highly recommend the serious pyrotechnician to purchase it. You can find it in the books and video section of Skylighter's web catalog.



A Charcoal Cooker


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



There are as many ways to produce charcoal as there are pyro enthusiasts. There are certainly many approaches that are simpler than my method. I will try to point out the advantages of this particular charcoal cooker and leave it to your judgment to determine whether it has merit. As always, I invite critical commentary, but praise and homage is preferred.

This is a typical 22.5 quart or 6 jar canner pot. It is used to can fruits and various garden grown produce. The pot is constructed of fairly light weight sheet metal which has a tough porcelain finish. It comes with a wire basket which holds the canning jars securely inside during the canning process. You can purchase one of these at Wal-Mart type stores for about $14.00. This is used as the "oven" part of the charcoal maker. There are many alternatives to using this particular kind of pot. Various metal drums or metal buckets will work just as well.
A lid for your "oven" must be fashioned with a hole in it where the hot gases can exit. The idea is to create a draft of hot gases from the bottom of the oven to the top. If you use this kind of pot, it's a good idea to cut the hole with minimal damage to the surrounding porcelain.
Next, the holes in the bottom of the pot are made. I placed a length of 3 inch paper mortar tube with its face against the inside bottom of the pot, beneath the site of each hole. This gives firm support to the bottom surface which avoids cracking the porcelain while the holes are formed. A sharp blow with a hammer on a center punch creates a hole about 5/16 inch in diameter. I created 30 holes in an evenly distributed pattern on the entire bottom of the pot.
Now, the theory is that the oven temperature could be regulated by the number of holes in the bottom. More holes allow more draft and consequently a hotter fire. I tried to create the holes in groups that would accommodate the addition of rotating hole covers. This should achieve the desired temperature regulation, but I have yet to experiment with this concept. Currently, the 30 holes result in an oven temperature of about 575 degrees F. Another enhancement would be the addition of standoff feet on the bottom of the cooker. I just set the pot on 3 rocks during operation.
Now we turn our attention to the retort container. This pot is a miniature version of the oven pot. I bought it at a garage sale for $1.00. Wood stove cement and fiberglass gasket material were used to seal the lid which is held in place by 4 mini C-clamps. A single 5/16 inch hole was punched in the lid to vent the smoke from the retort. I like this retort can because it will last for dozens of uses before it will need to be replaced. The handle is handy for lifting it in an out of the oven with a wire hook.
Many simpler alternatives can be considered for the retort container. These Christmas cookie cans work great. Add a couple of screws to hold on the lid, put a hole in the top or bottom and you're all set. (Editorial comment: You know you're a pyro when you buy stuff you don't need just to get the container. I don't care for these cookies, but I will gag them down just to justify buying the can.) My objection with this approach is that this kind of container will only last for about 5 or 6 roastings before the thin metal walls loose their integrity. Then I have to eat more cookies.
If you really want to become a gourmet charcoal cooker, you might want to consider buying one of these flu thermometers. This one cost $11.00 and was purchased at a hardware store that carries wood stove products. It is magnetic and will stay anywhere you put it on the retort if the retort is made of iron. Perhaps you are asking....Why do I care what the temperature is in my oven?
Let's slip into the theoretical domain again for a moment. Charcoal made at lower temperatures contains a higher percentage of volatiles in it. This leads to black powder that ignites easier, which would be desirable for black powder based primes. Charcoal made at higher temperatures contains less volatiles, ignites at higher temperatures and may be more desirable for creating lift and break powders. I don't know if there is a strong consensus among the pyro community for these theories. At any rate, the addition of the above temperature gage to your retort gives the appearance to the uninitiated that charcoal making is nearly as complicated as rocket science.
OK, we've finished making our primo charcoal cooker. Let's talk about how to use this hi tech apparatus. Perhaps the most labor intensive part of making charcoal is the preparation of the wood. When using willow, you must remove the bark and split the sticks into smaller sticks no thicker than 1/2 inch. I load the retort as full as possible with the sticks oriented vertically.
Now we need a fire in the oven. I use two layers of regular barbecue briquettes to fuel the fire. I place the briquettes in the bottom of the pot with the wire basket in place. The handles of the wire basket are removed so they don't interfere with the placement of the retort. This keeps the retort from settling and choking off the intake holes at the bottom of the pot. My kids think it's pretty funny that I use charcoal to make more charcoal. I'm afraid they tell their friends, "He's a nice guy, but sometimes he ain't too bright!" This picture shows the cooker in operation. The flu temperature gauge is placed so it is visible from the hole in the lid. A nice column of smoke is rising from the retort vent and the smell of smoky campfire fills the air (and sometimes my house when the wind is right.)
A close examination of the smoke column reveals an interesting fact about the operation of this cooker. The smoke is not visible until the gas jet rises several inches above the retort vent. This implies that the escaping volatiles don't condense into visible smoke until they cool in the rising column. This is the main advantage of this kind of charcoal cooker. Allow me to explain...
In my days as an apprentice charcoal maker, I would simply place the retort can over an open fire. I found that it was difficult to achieve a steady, well controlled heat source. I had to constantly add fuel to the fire and check it often. Even with great attention, the heat was not distributed evenly. The result was that there were often cool spots in the retort where the charcoal was brown instead of black, indicating that the wood conversion to charcoal was not complete. Even worse, cooler areas of the retort lid would allow condensation of the reaction gases on the inside of the lid. The accumulation of these tars left a mess that was impossible to remove. All of these problems are eliminated by the new cooker. Now, the retort stays fairly clean, I don't have to constantly tend the fire and the temperature is even and controllable.
Finally, the result of all this effort is beautiful, almost shiny black charcoal. Getting it into usable form is another story. I use a meat grinder for the first stage of reducing it to useful grain sizes. It was suggested in the April 98 AFN that you use gallon size zip lock bags, remove excess air and whack and roll it with a PVC pipe. The resulting charcoal powder is then graded with various screens. For airfloat, of course, you will need a ball mill. Whatever your method, you will get pretty grubby and will probably blow black stuff in your Kleenex for a week.



A Home-made Balance Scale


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



If you want to get into amateur pyrotechnics, a scale is essential. A commercial triple-beam balance scale can cost $85 to $100. Electronic scales will cost you at least as much. If this kind of expense is a big obstacle to your pyro ambitions, then you might be interested in this low cost plan to build a balance scale.

The heart of a balance scale is the balance beam. This plan uses a piece of hobby poplar, 1/2" X 1 1/2" X 16". You make a low resistance fulcrum with two sheet rock screws which protrude slightly from the beam to form the bearing points.
Some careful precision is needed to ensure that the screws are placed on a line which is perpendicular to the line of the beam. I used a T-square to draw the line and a drill press to drill guide holes for the screws.
The ends of the beam are constructed as shown to lower the swivel point of the weight pans. This is done by simply gluing another block of poplar to the bottom of the beam at each end. Next, the hooks are added from which the weight pans are hung. Finally, pieces of threaded rod are screwed into the ends of the beam and 2 or 3 nuts are screwed onto the rods. These are used as adjustment weights to cancel any asymmetries in the balance beam.
A pointer stick may be added to make it easier to detect when balance has been achieved while measuring chemicals. I used a left over piece of a model rocket kit and sharpened one end for the pointer. This is simply glued on with help of a square for alignment.
Weight pans can be suspended from the beam ends in many different ways. My first method used 2 loops of nylon kite string threaded through a square piece of fiber board bathroom paneling. A later improved method used coat hanger wire to support the weight pans.
The final part of the project involves constructing some kind of a stand for the fulcrum bearing surface. This can be accomplished with a simple vertical piece of wood which has a small metal plate mounted on top. A shallow groove is scored in the plate and the sheet rock screw points of the balance beam are placed into the groove. I used a surplus microscope stand for my scale. I then made weights from pieces of plumber's solder which were weighed on a high precision electronic scale and trimmed to the desired weights. The final result is a scale which is highly accurate and incredibly cheap to make.



Ball Milling Jars


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



As with most home-made tooling, there are many ways to make milling jars. I have yet to see a design I like better than this one which uses PVC pipe and fittings. The jars are very sturdy and will last for many years. Their initial description was supplied by Lloyd Sponenburgh.

The quart size jar uses 4 inch PVC and fittings. It is the smallest and cheapest jar to construct. However, its milling capacity is so small that it is only useful for small batch, specialty milling. This is the parts list: a 4 inch end cap, a 5 inch length of 4 inch I.D. schedule 40 PVC pipe, a 4 inch to 3 inch reducer, a short stub length of 3 inch I.D. PVC and a rubber test cap with band clamp.
The above parts are all glued together with PVC glue to yield this result. As you can see, the jar with the flat end cap is nice because it will stand up by itself. If you use a rounded end cap, I recommend putting 3 rubber feet on the bottom of the end cap to stabilize it. The rounded end cap also results in a larger capacity jar. The actual total capacity of the flat bottomed jar is about 1 quart plus 1/2 cup. It will require a volume of 1 pint plus 1/4 cup of milling media and will yield a charge of 1 and 1/8 cups of milled powder. This illustrates the Sponenburgh rule of thumb for milling jar capacity which is: Fill your jar half full of milling media to mill a charge of 1/4 of the jar volume.
The 5 inch jar is about right for most of my milling jobs. The same parts as above are needed, but in the 5 inch sizes. There are a few quirks, however. The supplier in my area does not carry a simple 5 inch to 3 inch reducer. The reducer shown fits inside the 5 inch coupler. This requires the addition of the coupler to the above parts list. The other complication is that there are lots of ridges and raised lettering on the outside of the coupler that have to be removed to achieve a smooth outer surface on the jar.
Shown here is the rounded end cap, a 6 inch length of 5 inch I.D. PVC and the coupler with the raised ridges removed. A radial arm saw was used to remove the ridges, but a belt sander would probably work better.
When these three parts are glued together, the 6 inch length of pipe becomes entirely enclosed by the coupler and endcap because the distance of insertion into each one is 3 inches.
The reducer is prepared by clipping off the corners which otherwise would protrude beyond the outer surface of the jar. A short length of 3 inch PVC is cut so that 3/4 inches will protrude for the attachment of the rubber test cap lid. Note that the lid in the next picture has been trimmed back to a width of 3/4 inches to make it much easier to attach and remove.
The final volume of this jar is 3 1/4 quarts and the charge capacity is 3 1/4 cups. Again, the addition of stick-on rubber feet to the bottom of the rounded end cap is recommended. A few final notes: Mill jars, like screens should be reserved for certain classes of milling. I have separate jars for milling black powder, oxidizers, (chlorates get their very own jars) benzoates and binders. Care should be taken with your milling media, as well, to avoid cross contamination. I use ceramic media to mill most single substances. Lead media is used to mill black powders, rocket fuels and charcoal. This same approach can be used to make milling jars of 1 gallon capacity by using 6 inch PVC pipe and fittings. The drawback is that a jar of this size will require 30 pounds of lead milling media. That represents a big pain in my back to lug around and in my wallet to purchase the media.

I couldn't find the rubber end caps in my area, but the 3" ABS test caps fit right on the outside diameter of the 4" to 3" adapter tightly, no clamp required.

I have read information indicating that PVC will not show on X-Ray. This requires exploratory surgery to locate fragments in the human body as PVC will cause severe infection if not removed.  To solve the problem I purchased a six inch HDPE mortar, cut it into 14 inch lengths and purchased six inch pipe plugs to close the ends. The plug is called "Gripper" and is manufactured by Cherne Industries, Inc. They come in various diameters. I purchased the 6 inch plug at Schimberg Co., a plumbing supply company, here in Cedar Rapids, Iowa for $16.91. These are kind of costly, but these jars are very easy to clean and if detonation were to occur there would be no risk of shrapnel.

I have a tip on stabilizing ball milling jars. Instead of applying rubber sticky feet to the jars, just cut an inch or so tall cylinder of the same pipe used in the jar and glue this to the convex bottom of the endcap. This results in a very stable base that is accurate and also very durable.




Easy Pyrotechnic Screen Boxes


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



Conventional wood framed screen boxes are usually about 1 ft. square and 3 or 4 inches deep. I find this much screen area to be more than is necessary. Cleaning them is difficult because of all the corners. Stacking them for multiple grain separations is awkward unless extra rails are added around the tops of the frames. Then you have more corners to clean. All these problems can be solved by using plastic storage containers as frames.

This is a typical shoe box size plastic storage container. They have very smooth, water-proof surfaces and rounded corners for easy cleaning. They should have stop tabs on the exterior which allow you to stack one inside another with about an inch of clearance between the bottom surfaces. They seal fairly well when stacked to control dust nicely.
First, get a sharp utility knife and cut out the bottom of the container, leaving about 1/4 to 1/2 inch of a lip around the edges. Usually the container will have a raised ledge molded into the bottom which makes a good guide for cutting.
Now cut your screens to size so that the screen is larger than the hole in the bottom of the container. You should be able to get 2 screens from a square foot of screen cloth. Two for the price of one!! Now, you will need some good tape (duct or strong masking tape) and some good quality epoxy glue.
Before applying the epoxy, you should rough up the gluing surface of the plastic with some coarse sand paper.
Then mix up the epoxy, apply along one edge, put the screen in place and apply the tape over the screen where the epoxy is. The tape should hold the screen tightly against the container frame while the epoxy sets. Now repeat the procedure for the remaining three sides. If you have a well behaved screen that lies nice and flat, you might be able to get away without using epoxy at all and only use the tape. This is much less trouble, but also much less durable as you can imagine.
Voila!! The finished result is a compact, stackable, light weight set of screens with a convenient catch box which is merely another unmodified container. I'm so pleased with them that I seldom ever use my original, wooden box screens any more.

Your screen idea is neat. Mine are nearly the same, except:
a. I put my screens on the inside.
b. I fasten them down with automotive "blue goo" so they are very easy to take off and replace.


A Powder Die


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



This powder die design was invented by Lloyd Sponenburgh. In fact, this die was even made by Lloyd because I bought it from him when he was still in the business of selling BP making tools. Unfortunately, Lloyd no longer sells this useful item, but you can fairly easily make your own. He has, however, described how he makes them in the pyro news group. I assume he won't mind if I do the same on this web page.

This is the base of the powder die. It consists of a five inch length of 3 inch I.D. PVC and a base cylinder of cast resin. The cylinder looks a little blotchy because of black powder stain and is quite heavy because of its length. The only utility of this exaggerated length is the avoidance of excessive blocking if you use a press with high clearance. A much shorter, lighter base would still work just fine. Notice that the PVC sleeve is held fixed, relative to the base cylinder, by a set screw. The function of this sleeve is to position the cylinder a defined distance into the compression sleeves pictured below.
The compression sleeves are made from a 3 inch length of 3 inch I.D. PVC and a "repair sleeve". The repair sleeve is similar to a coupler, except it has no stop ridge in the center. Both of these sleeves have been split by cutting with a very narrow kerf blade down the length of the sleeve. In use, one sleeve fits inside the other, with the splits opposite each other, and they are restrained from expansion by two common pipe clamps.
When placed on the base, the compression sleeves form the walls of the chamber where black powder meal is placed to be pressed.
The top piston is another cylinder, similar to the base cylinder, which has been made from a casting of resin. Read the feedback at the bottom of the page from Lloyd to find out about how to make these castings.
The top piston is placed into the compression sleeves after the black powder meal and pressed until a known density has been achieved. On this top piston, a groove has been placed to indicate that when it is even with the top of the compression sleeves, 8 ounces of meal will be at the desired density of 1.7 grams per cubic centimeter. Likewise, 4 ounces of meal are pressed until the top of the piston is flush with the top of the sleeves. The press cake that results from this pressing process will be very hard and sounds like china when tapped. After corning, you will have a very durable, hard grained powder.

I'll gladly supply the composite formula for you, but when you hear it, you'll DIE of laughter.

I wanted something that would both lower the cost of the resin casting and provide a strong matrix. Chopped fibers were out for cost, and organic fillers for lack of strength. I settled on 'sharp sand'. No kidding!! It's called sharp sand in some circles, mason's sand in others. Sack Crete Corp. puts it up as 'fine blasting sand'. River sand is smooth, and makes a weak matrix. Add sand to mixed polyester resin (fiberglass resin) until it makes a very thick but still pourable batter. If I recall (without my docs book in hand) about 24 fl.oz. of resin to one quart dry measure of sand works out about right. I cut back to about 60% of the recommended hardener, because the large castings get very hot, and will crack as they cure if you add too much hardener. You want enough sand so that no resin 'settles out' to the top after you fill your forms. The ratio is fairly critical, but quite easy to discern. If liquid resin rises to the top after pouring, you need more sand next time. DO make sure your moulds are accurate. You'll never cut this stuff after it's cured. The silica makes ALL metal tools go bye-bye on the first contact. I had to mill the calibration grooves in my pistons with a solid carbide bit, and that had to be sharpened every two or three cuts.

I mix Vaseline with toluene as a mould release, and simply paint on a VERY thin layer with a soft bristle brush. The Vaseline will melt with the heat of the casting, so go sparingly, or you'll have a puddle of grease on your resin as it cures. My moulds were cleaned-up pieces of PVC DWV pipe clamped to a foil-covered piece of aluminum plate. The resin shrinks slightly on cure, and the castings just slipped out without any difficulty. But if a casting stuck, I could unclamp the pipe from the base plate, and push the casting out from one end.


Due to several requests for exact dimensions, I have added the discussion below to clarify the design of the powder die.

The top piston ram is 5.36cm high.
The 8 oz. mark is 1.46 cm below the top.
The base cylinder enters the compression sleeves by 0.8cm.

Now for the math just to verify the theory.

The compression sleeves are 3 in. or 7.62cm long.
Subtracting the size of the top ram and base intrusion:
7.62 - 5.36 - 0.8 = 1.46 cm for a 4 oz. BP cake
and 2.92 cm for an 8 oz. cake. These are the cylinder
lengths (L) for each cake.

The volume of a cylinder is (PI * (D/2)**2) * L where
D is the diameter and L is the length.
For the 8 oz. cake this becomes 3.14 * 14.516 * 2.92 = 133.16 cc.

Since 8 oz = 226.8 grams, the density becomes 226.8/133.16 = 1.703 grams/cc.

It works!

Hey Dan,

I finished the BP Die design program this morning. I have written this program for you and all who wish to use it. If you feel this program worthy I will leave this link for all to download or feel free to add the program to your URL or what ever pleases. I can add or change any function. Just let me know. The program is 780k. The link is: http://www.amasa.com/BPdie.exe

Thanks, Mike



A Simple Hydraulic Press


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press



This was one of my most enjoyable projects! It was done without great expense or special tooling. There are many ways to build a press with this approach. Maybe this particular plan will give you some ideas for building your own.

These first pictures show some of the major component parts of the press. This is one of two pieces of 4 inch wide channel. They are 16 inches long and are used at the top and bottom of the press. They are useful for mounting eye bolts and the blast shield as well as providing a space in the base for the large pressure bearing nuts. I chose to drill the two holes where the 3/4 inch threaded rod goes through. The task of drilling holes in a piece of channel is not nearly as daunting as drilling through 3/4 inch flat bar as shown below.
This picture shows one of three pieces of 4 inch wide flat bar. They are 3/4 inches thick and 14.5 inches long. A notch has been cut in each end to accommodate a 3/4 inch threaded rod. As you can see, the cutting is very rough because it was done with a simple cutting torch by the metal dealer. These three pieces cost me $15 and the torch cutting cost another $5. You very well might do better if you try to find this material from a scrap dealer.
This is the six ton hydraulic piston jack. I purchased it from an auto parts store for about $20. The force of this jack is sufficient to bend the pieces of channel. This is why I needed to use the pieces of flat bar to reinforce the channel pieces at the top and bottom.
This is a piece of 1.25 inch thick Plexiglas that I used for the blast shield. I was very fortunate to receive this free from Donald Haarman who apparently salvaged it from a dumpster. Thanks again, Donald!! Part of the fun of these projects is the "scrounge" phase. Whatever is used for the blast shield, it's very important to include it. I certainly feel a whole lot safer with 1.25 inches of Plexiglas between the press and my face.
This close-up view of the top shows the channel placed on top of the flat bar. The threaded rods hold them both in place with a nut and washer on each side. The blast shield is bolted to the channel through a wood offset block. This gives me a little more working room around the middle pressing deck.
The base of the press is assembled identically to the top. The retraction springs are attached to eye bolts which are mounted through the base channel.
This picture shows the attachment of the blast shield to the base channel. You can also see the bolt which secures the base of the hydraulic jack to the base of the press frame.
This view from the opposite side of the blast shield illustrates the attachment and placement of the retraction springs. The springs add stability to the middle pressing deck and conveniently retract it when the release valve of the jack is opened. These springs are fairly expensive at $2.85 apiece, but are well worth the contributions they make to the design.
Finally, the finished product is shown. This press design was partially inspired by a similar plan sold by Firefox Enterprises. The major difference is that the Firefox design places the hydraulic jack on top of the pressing deck and the object to be pressed is placed on the base of the pressing frame. This way, the pressing surface comes down from above, whereas the design shown here causes the pressing surface to push up. If you are interested in the Firefox design, it only costs $4.00.

This idea comes to you from Rich Weaver. I liked it so well, I made the modifications to my own press. The concept is to add protective sleeves around the threaded rods to prevent the press deck from scraping against them as the deck is raised and lowered. I made the sleeves from 3 inch lengths of 3/4 inch PVC conduit pipe. I glued a coupler on one end and then cut the coupler right down the middle. The PVC tubes had to be notched a little to allow them to fit into the slots of the press deck.
The sleeves are installed by using the coupler rings that were cut off in the step above. The rings are glued and slid over tubes to lock them into place in the slots of the press deck as shown. The tubes now act as guides that give the deck a little more stability and keep it from binding or scraping against the threaded rods.

I think arc welding the head of the jack right to the metal plate would help to keep the item(s) being pressed perpendicular to the plates. -Mike N.

Mike N. suggested arc welding the jack piston directly to the pressing deck. I suggest arc welding a 4"X4"X1/4" thick plate to the jack piston in case you ever need to take the press apart. -Robb W

Robb W. suggested arc welding a 4"X4"X1/4" thick plate to the jack piston in case you ever need to take the press apart. I suggest arc welding a large socket to the 4x4x1/4 plate (large enough to accommodate the jack piston) in case you ever need to replace the jack :) -Steve K


Ball Mill - Charcoal Cooker - Scale - Milling Jar - Screen Boxes - Powder Die - Hydraulic Press


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