September 23, 2010
The development of gunpowder has become the longest thread of technological development in recorded history. Every time you squeeze the trigger and touch off a round, you're doing more than sending lead downrange. You're taking part in history.
Gunpowder was discovered around 850 by Chinese alchemists. Since that time, development of gunpowder has become the longest thread of technological development in recorded history. In turn, gunpowder has had a major impact on history. Gunpowder forever changed the face of warfare, enabled monarchs to build nation-states, and advanced science. Perhaps most important, gunpowder made all men equal, as personal safety no longer depended on physical strength or training.
Gunpowder is at once an art and a science. The science is in the understanding of the physical nature of the substance. The art is in the application of this knowledge by gunners.
Although the development of gunpowder was fitful and haphazard, many famous men of history were involved in this effort. To mention just a few, we could include Roger Bacon, Leonardo da Vinci, Michelangelo, Issac Newton, Antoine Lavoisier, Alexander Forsyth, E.I. DuPont, Thomas Jefferson, Benjamin Franklin, and Jefferson Davis.
Blackpowder is a mechanical mixture of three natural ingredients that do not undergo chemical change during manufacture: potassium nitrate, charcoal, and sulfur. Tests in the late 1800s confirmed the ideal mixture of the components to be: 75 percent potassium nitrate, 15 percent charcoal, and 10 percent sulfur.
By comparison, smokeless powder is a mixture of ingredients that undergo chemical change during manufacture. The basic ingredients are cellulose and concentrated nitric acid in the presence of sulfuric acid. This process is called nitration as it adds nitrogen and oxygen atoms to the cellulose molecules. The nitrated cellulose--now nitrocellulose--is then dissolved in a mixture of ether and alcohol to form a colloid that can be rolled into sheets or extruded into rods, dried, cut into flakes or tubes, and then coated with graphite.
How Blackpowder Works
When ignited, blackpowder burns--deflagrates or releases stored energy--at a temperature in excess of 2,135 degrees centigrade, forming hot, rapidly expanding gases. These gases are a product of potassium nitrate oxidizing the sulfur and charcoal in a complex series of reactions to form three gases--carbon dioxide, carbon monoxide, and nitrogen--and three solids--potassium carbonate, potassium sulphate, and potassium sulfide. Taken together, the three gases constitute approximately 45 percent of the products of combustion, while the remaining 55 percent are solids that make up the smoke and residue left in the gun barrel. The sulphide is the cause of the stench in powder smoke.
In generating these gases, the volume of the blackpowder expands more than 3,600 times, releasing heat and creating pressure in the order of 20 tons per square inch. Blackpowder will burn equally well in a vacuum, as the potassium nitrate provides the oxygen for the reaction. In its normal form of randomly shaped grains, blackpowder is not progressive burning.
Blackpowder can be made without sulfur; however, such powders are hard to ignite. Sulfur lowers the ignition temperature and improves homogeneity.
As the large, water-driven wheels rotated around the table, their great weight incorporated the ingredients for gunpowder in one-fourth of the time needed by stamping mills.
Image courtesy of Hagley Museum and Library
Smokeless propellants have considerably more energy content than blackpowder. As they burn, smokeless propellants release energy in the form of hot, expanding gases that are comprised of carbon monoxide, carbon dioxide, nitrogen, hydrogen, and water (steam). Unlike blackpowder, smokeless propellants convert nearly all of their solids into gas and leave little residue. The shape of smokeless propellant grains is a major factor in producing a progressive burning rate.
How Blackpowder Is Made
Manufacture of blackpowder is a seven part process:
The three ingredients and a small amount of distilled water are placed under an incorporation wheel. As this large stone or iron wheel rotates, it crushes the moist ingredients together under tons of pressure. The result is called "millcake."
The moist millcake is placed in a press that reduces its volume by about half. The result is called a "presscake."
The still-moist presscake is allowed to dry thoroughly.
The dry presscake is broken up into small, irregular grains.
The grains are sorted according to size in a sieve stack.
The powder grains are rumbled in rotating wooden barrels with graphite powder.
The finished blackpowder is placed into containers by weight.
Manufacturing ImprovementsAround 1400, the first stamping mills were developed to replace hand incorporation. A stamping mill consisted of a series of mortars and pestles operated by hand power. The three, dry ingredients were placed in each mortar and then worked and crushed by the pestle for 24 hours. This was difficult, dangerous work, and accidental explosions were common. The result was a dry powder called "serpentine." These stamping mills were replaced about four centuries later by roller-wheel-mill incorporation, which was safer, faster, and cheaper.
By about 1500, a second improvement in blackpowder manufacture called "corning" was developed. In an effort to reduce the number of accidental explosions during incorporation, gunners began adding a small amount of moisture to the blackpowder to reduce dust and friction. The resulting moist paste was formed into large loaves called "dumplings" for transportation. At the gun site, the dumplings were crushed into small pieces by hand. The corning process mixed the ingredients much more closely, and it was quickly found that not only was corned blackpowder more reliable than serpentine, it was much more powerful. Gunners quickly appreciated that the space between the powder grains was the cause of this, so they started deliberately making blackpowder into grains by forcing the moist paste through scree
ns, then sorting the dried grains in sieves.
Stamping mills were used to incorporate the ingredients of gunpowder. This operation was difficult and dangerous. Accidental explosions were common.
Image courtesy of Bayerische Bibliothek Munich
Developed in France in the early 1800s, the pressing process consisted of placing a moist millcake into a screw-press, then applying 1,000 pounds of pressure. The pressure reduced the volume of the cake by about half. This produced a dense, more powerful product and allowed a lesser amount of propellant to be used.
In 1857, Lammont DuPont patented an improvement in the historic formula for blackpowder by substituting sodium nitrate for potassium nitrate, thus creating "soda powder." Sodium nitrate-based gunpowder was voraciously hygroscopic, which DuPont tried to reduce to acceptable levels by applying a heavy coating of graphite. Alas, sodium nitrate-based gunpowder was found to be excellent for blasting but useless as a propellant.
During the Civil War, the Confederate government constructed an ultramodern blackpowder factory in Augusta, Georgia. General George Washington Rains, C.S.A. was given responsibility for constructing this facility. He found that removing impurities in the potassium nitrate, especially chlorides, made a big improvement in powder quality. Accordingly, he used triple-refined potassium nitrate to remove chlorides, made additional efforts to purify sulfur, and used temperature-controlled kilns to make charcoal. The result was an outstanding gunpowder, one that was cleaner burning and that produced far less smoke than powder from other sources.
Gradually, it was appreciated that the species of tree from which charcoal was made was also important. Willow, alder, chinaberry, hazelwood, and grape vines proved to have the delicate structure and minimum ash content for making gunpowder. Burning the charcoal in a temperature-controlled kiln also improved the quality.
Brown (cocoa) powder was the highest form of gunpowder before the advent of smokeless propellants. In 1882, German technicians formulated a new gunpowder that contained 2 to 3 percent sulfur and underburnt charcoal made from rye straw. Although brown powder proved hard to ignite, it offered ballistic performance that rivaled early smokeless propellants. However, in the short span of 10 years, brown powder became redundant and disappeared.
When smokeless powders became common by 1900, some competitive rimfire shooters insisted there was no substitute for blackpowder in .22 rimfire match ammunition. For this group of shooters, ammo manufacturers developed .22 rimfire ammunition loaded with semismokeless powder that was a mixture of blackpowder and smokeless propellants. By the early 1930s, the advantages of smokeless propellants in rimfire ammunition had become completely evident, and cartridges loaded with semismokeless powder became obsolete.
Blackpowder is extremely sensitive to heat, sparks, static electricity, and impact. Throughout history, accidental explosions in manufacture, handling, and storage of blackpowder have been common. For these reasons, blackpowder has been placed in a more hazardous shipping classification than smokeless propellants. Blackpowder commands respect and must never be taken for granted.
Blackpowder is very hygroscopic. As the moisture content rises, the energy of the blackpowder drops noticeably. And it does not take much; even a 1 percent increase in moisture content will reduce performance. Blackpowder that has been wet should not be used. Although the wet powder can be dried out, the moisture destroys the intimate mixture of the ingredients to an extent that cannot be reversed.
A New Name
The advent of smokeless propellants in the mid-1880s created the need for a semantic change in the description of gunpowder. For almost 1,000 years, the term "gunpowder" had only one meaning. By the 1880s, there were several confusing possibilities. In short order, the term "gunpowder" was transferred to the general species of smokeless propellants, while the term "blackpowder" became the term for powder made from the historic formula. These distinctions continue today.
Is there a future for blackpowder in the modern world with so many viable and effective blackpowder substitutes available? In short, yes. Beyond traditional shooters who enjoy reenacting, competing, and hunting with blackpowder firearms, there remain several other uses for the historic formula. Many modern artillery-propelling charges contain blackpowder boosters, and blackpowder remains one of the popular fillers for model rocket engines and fireworks. Many burning fuses use blackpowder as the combustible filler. In short, there are many things that blackpowder still does better than anything else.