Generalities about Powder

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1. Introduction

The origins of gunpowder, while uncertain, was likely somewhere in Early Medieval China, prior to the formation of the Jin Dynasty (1115). Initially, usage of this material was limited to propellants; however, by the time of the Mongol invasion of Japan, its use as an explosive was recognized, and primitive forms of firearms--known as "fire-lances", began to make an appearance.

Soon, this technology spread along the Silk Route, and into the Near East, and Europe, where the potential for gunpowder weapons came to be realized. Early recipes for gunpowder are first attested in the two regions in the 13th century, and by the 14th century, primitive firearms and artillery began to make an appearance, in order to take advantage of the powder. At first, these pieces played relatively little role in Medieval combat: the bombards of the English Army at Crecy (1346), played a relatively unimportant role, compared to the decisive impact of the ancient technology of the longbow. However, with improvements in metallurgy, and improvements in the production of gunpowder, the full potential of this technology soon showed. By the beginning of the 16th Century, Gunpowder weapons were a common sight on the battlefield, and by the end of that century, had become the most important weapon systems available to the armies of the period. This trend continued through to the 19th century, when better propellant and explosives were introduced. By that time, firearms and artillery had come to completely dominate the modern battlefield.

The reason behind the eventual success of gunpowder, and the weapons that utilized it, are relatively straightforward: the chemical nature of the energy emitted by the burning of gunpowder did not rely on the skill or training of the soldier to generate, in the way a longbow or hand weapon required. Additionally, the amount of energy released was sufficient--when properly harnessed--to hurl relatively small projectiles with great force, sufficient to defeat any armor of the period. The combination of the two factors meant that a soldier could be trained to defeat any opponent at range, with little training or effort; the greater part of raising an army was invested into the weapons and equipment itself. This then began a process where greater armies could be raised, at reduced cost. By the middle fo the 18th century, whole armies were equipped with weapons primarily dependent on this mixture.


2. Properties of gunpowder

2.1.Basics of gunpowder: chemistry

All gunpowder (which refers to what is now called "black powder") is composed in effect, of three components:

  1. An oxidizer
  2. Fuel
  3. Matrix constituent

The oxidizer--traditionally composed of Potassium Nitrate (KNO3), common called Saltpetre or Nitre--serves to provide oxygen to consume the fuel, which in this case is carbon, in the form of wood charcoal. To maximize the energy of the reaction between the two components, and also stabilize the rate of the reaction for greater reliability and uniformity, sulfur is added as a matrix constituent. The above chemicals could be substituted--notably sugar in place of charcoal; however, these would be less that ideal.

Traditionally the ratio between the ingredients was 75% saltpeter, 15% charcoal, and 10% sulfur, which is quite close to the ideal; while this is not the optimal ratio, it is quite close to it, and is still the standard for gunpowder to this day.

The reaction of all three components is precipitated by the introduction of a heat source--a flame or spark, which produces a series of gasses, as well as sulfate and carbonate salts, alongside a series of other assorted chemicals which result from partial combustion of powder--sulfides, cyanites, etc.

The salts and other solids, alongside unburnt powder, are what produce the fowling that plagued all weapons of the period on firing. The gases--or rather, their rapid expansion--are what generate the energy needed to propel the projectiles. If sufficiently confined, the same effect can also generate a explosion--useful for the production of artillery shells. Additional chemicals, particularly sulfides, sulfates, and unburnt sulfur, will also generate the distinct rotten-egg odor of burnt powder.

The gases generated, when combined with the impurities and partly burnt powder, create the distinctive blue-grey smoke associated with gunpowder, which becomes whiter the greater the quality of powder. As most of the gases are heavier than air, these tended to settle readily, and stay in the air for extended periods of time; large quantities of powder spent could thus cloud the field in a dense haze or fog--the famous "fog of war", which hampered visibility on battlefields of the time.

2.2.Production

Gunpowder can be simply produced, by the direct combination of saltpeter, sulfur, and charcoal. These can be ground into each other to produce the powder. The mixing is traditionally done in a ball mill, which contain heavy balls--traditionally lead; this ensured the most even mixture possible, and also reduced the chances of an explosion. The result is "serpentine" powder. While relatively quick to make, the components tended to separate when transported over any distance, and had to be remixed when the time comes for battle. This virtually guaranteed that the powder quality was unpredictable, even within the same batch. It also created a heightened risk of accidents, both during production and afterwards.


To counteract this, corning was invented. This involved the following steps:

1-The powder would be mixed, as with the production of serpentine powder; however, the mixture is also mixed with water: this ensured a more even mixture, and greater safety, as the water prevents combustion altogether. 3-the powder is then pressed into solid blocks, called cakes, which are then dried. It is important at this stage that the density be relatively uniform (typically ~1.7 gm/cm^3, though this varied according to the specifics of the ingredients) 4-the cakes are then ground into granules 5-The granules were then finally sorted by granulation.

Sources of ingredients

Charcoal is the easiest of the components to obtain, as it is readily produced from wood. The best wood currently available is pacific willow; however, this was not available in the Seven Years War, as the Pacific Northwest had yet to be settled. However, various species were available in Europe, which were almost as good: willow, laurel, elder, or hazel. If necessary, wood could be substituted with pine cones. These all have the benefit of being relatively light, and with a structure that increases surface area--thereby increasing charcoal quality.

Sulfur could be mined, from various parts of Europe. However, Italy proved to be the best source for the element, and had been since Roman times.

Saltpeter was the hardest material to either find or produce: the high solubility and instability of the chemical, especially in warm weather, limited production to either a few mines found in arid regions, or in areas of high latitude or altitude. As a result, Switzerland was the best source of saltpeter in Europe, as much of the country is mountainous, and so has many areas of high latitude, with corresponding low temperatures. There and in other parts of Europe, saltpeter production involved the following steps:

1-Manure is collected from the fields; this was a heavily-regulated industry, as the manure was also needed to fertilize the fields. 2-This is then allowed to decompose, in order to produce some of the precursors to saltpeter. 3-the manure is now leached and boiled. This created a solution of calcium nitrate. 4-to the solution is now added potash and sodium nitrate, which caused the precipitation of calcium carbonate. The remaining liquid contained the dissolved saltpeter. 5-the liquid is then cooled, which allowed for the precipitation of the saltpeter, which could then be collected.

In areas where high altitudes/latitudes were not available, the process was either done in the winter, or the gunpowder was simply imported.

2.3.Types and Performances of powder

Powder in this era was generally corned--that is, the mixture had been converted into grains of relatively uniform size; this distinguishes it from serpentine powder, which is simply the direct mixture of the components. The corning of the powder allowed it to retain its quality longer, guaranteed a more even performance, and allowed for the production of different varities of powder, based on the size of the grains.

Specifically, the coarsest powders were used for artillery pieces. Finer powders were used for muskets, and the finest powders were used for smaller firearms (e.g. pistols), or for priming. The finer powders tended to burn more rapidly than the coarser powders, but also released their energy faster. As a result, a fine powder charge would release its energy too quickly for a heavy projectile, and either be wasted (which results in poorer performance), or cause damage to the weapon. In contrast, a coarser powder will prove inefficient for smaller projectiles, as its slower burn rate enures that the projectile will be launched well before enough energy is released, which results in a under-powered projectile.

In addition to the granulation of the powder, the quality of the materials is also important: impurities in the saltpeter, as well as the structure of the charcoal (which is dependent on the type of wood used), can affect the performance of the powder. Improper storage can also affect the powder--especially if the powder is exposed to sufficient levels of humidity.

To illustrate the importance of quality on the performance of weapons from the period, the results of a test, conducted on the 11th of August, 2019.(temperature was ~25 Degrees Celsius, and at ~1370m above sea level. All tests involved paper cartridges, with a .69 caliber ball and powder charge, fired from a replica M1730 Brown Bess Musket:


Powder type charge (volume) mean density per charge (grains/125-grain charge) mean muzzle velocity (m/s)
Goex Fg 125 grain 114.8 274
Goex FFg 125 grain 126.6 305
Goex FFg 165 grain 126.6 335
Graf 125 grain 126.3 295
Old Gynsford 125 grain 123.7 311
Swiss 1.5F 125 grain 123.5 334


N.B: the results should not be interpreted as an endorsement or condemnation of the powders. This is especially as each of the above is suitable for a variety of functions.


As can be observed, the coarser-grained powder (Goex Fg), performed at noticeably poorer level, when compared to the other powder types. In addition, the better ingredients used in the Swiss 1.5F powder produced markedly superior results to the comparably grained powders in the list, which was the closest in granulation to 1.5F Swiss). Similar variations in quality would have been common during the Seven Years War, and for a long time afterward. tellingly, the Swiss 1.5 F, with a 120-grain charge, performed as well as Goex FFg with 165 grains of powder. This explains why it was common in the British army to under-charge their cartridges, with the official charge in 1775 set at 165 grains, but most cartridges in practice had up to 25% less powder (~125 grains); period treatises stated that this was to account for higher-quality powder.

An additional effect of the variation in gunpowder quality is the effect on the user: the greater energy of the Swiss 1.5F powder resulted in a noticeably heavier recoil, which proved unpleasant. This heavier recoil would have naturally affected the accuracy of the weapon over longer distances.

Finally, there is an upper limit to the muzzle velocity of the shot, based on the volume of the powder used. This is because the use of sufficiently large quantities of powder will lead to incomplete combustion, as the energy generated by the gunpowder is sufficient to blast out the excess gunpowder, before their combustion could add to the muzzle velocity of the piece. As a result, it was considered ideal for the powder charge to weigh anywhere from 25% to 33% of the projectile, depending on the quality and granulation of the powder (so an ~490 grain projectile could use as much as ~165 grains of powder--hence the British setting a Brown Bess charge to that weight).

2.4.Actual Quality of Powder during the Seven Years War

While the various armies of the period did differentiate powders by granulation, the regulation of the quality of the powder was erratic, with differences in quality comparable to those between the powder types mentioned above. This had an adverse effect on both the quality of firepower--here due to the erratic muzzle velocities of both cannon and musket--a powder which i either too strong or weak could make a projectile overshoot or undershoot a target, particularly at the tactical ranges of the period; the Swiss 1.5F Powder for example, would have produced a point blank range 20 yards greater than that of Goex FFg. As most firefights were fought between 100-150 meters, the difference in where the projectiles would land varied excessively.

The erratic quality of the powder affected the quality of the pieces themselves. A poor powder, if used for proofing, will be less likely to expose serious defects in a weapon, which could then endanger the user of the weapon.

As a result, the various armies of Europe in the post-Seven Years War era gradually took steps to improve and standardize the quality of powder available. This led to the higher quality weapons of the Napoleonic Wars: even the Brown Bess of the time, though far less ornately decorated, were more reliable and effective weapons compared to their counterparts of the Seven Years War.

References

Bräker, Ulrich, Der Arme Mann im Tockenburg, 1789

Rosen, M.A., 2006, Historical Aspects and Black Powder Manufacturing, Civil War Artiller project, http://www.civilwarartillery.com/disarm/blackpowder.htm accessed 8/15/2019

Acknowledgments

User:Ibrahim90 and W.D. Liddell, for the initial version of this article