Friday, December 30, 2016

Smokeless Powders: Productionizing Gun Cotton: Early Experiments

In our last post, we saw how gun cotton was accidentally discovered. As was mentioned in our previous post, some early researches were done by French scientists, namely Henri Braconnot in 1832 and Theophile-Jules Pelouze in 1838, but the Swiss scientist Christian Schönbein in 1845, was the first to realize its potential to be used in firearms as a replacement for black powder. Schönbein sent out samples of his discovery to friends in England in 1846 and published details about his discovery, but kept his method of preparation a secret until he received a patent for his discovery. Schönbein also worked with a German scientist from the University of Frankfurt named Rudolf Böttger, who had discovered the same process independently during 1845, to improve the manufacturing process. By a strange coincidence, another German, a professor from the town of Braunschweig, Dr. F. J. Otto also made a similar discovery and published his process details in 1846 before Schönbein and Böttger,

The discoveries of Schönbein soon attracted the attentions of many other chemists (mostly French and German), who investigated the properties and chemical composition and came up with different variants. Some of these names include the above mentioned Pelouze (who revisited his earlier research and came up with a new process in 1846), Dr. Knopp, Dr. Bley, Von Kirchoff & Reuter, Porret, Teschemacher, Walter Crum and Dr. J.H. Gladstone.

In England, a company called John Hall & Sons Co. bought the patent rights to manufacture gun cotton from Schönbein in 1846 and built a new factory to do so at Faversham in early 1847. Unfortunately for them, the process and its associated dangers was not fully understood and a few months later, on 14th July 1847, there was a huge explosion that destroyed the factory and killed many workers, leading to the factory being closed soon afterwards. The manufacture of gun cotton was not attempted in Faversham again until 1873, when a different company opened a new plant at a new location outside town. But this was not the only tragedy -- only a year later, on 17th July 1848, 1600 kg. of gun cotton exploded in a factory at Bouchet near Paris. This explosion was so powerful that walls from 18 inches to a yard in thickness were reduced to powder, and heavy weights were hurled to great distances. These and other accidents, caused the French and German governments to appoint committees to study whether manufacturing of gun cotton was worthwhile or not. After 6 years of experiments, the French Commission reported that, "In the present condition of things, there is no use in continuing the experiments in relation to employment of gun-cotton in warlike arms."

However, all was not lost. Over in Austria, an officer named Wilhelm Freiherr Lenk von Wolfsberg (also known as Baron von Lenk and Von Lenk) was conducting his own experiments in 1849 on behalf of the Austrian military. Von Lenk was serving in a Field Artillery regiment when he began his experiments and he discovered the cause of the previous failures. He came up with a process of manufacture that was both safer and profitable. Due to his researches, a factory "K. K. Ärarische Schießwollanstalt" was set up in Hirtenberg to manufacture gun cotton in 1851. This factory was later absorbed into a larger artillery arms company that still exists today, Hirtenberger AG.

Major General Baron Von Lenk in 1865. Click on the image to enlarge. Public domain image.

The developments in Austria naturally attracted the attention of several European governments, and from England, a Major Young was sent over to Austria to learn everything that the Austrians were willing to disclose. In 1862, a committee was appointed by the British Association to inquire into the application of the new explosives for war purposes. The committee consisted of 3 chemists, the previously mentioned Dr. J.H. Gladstone, Professor W.A. Miller and Professor Frankland, and 6 engineers, William Fairbairn, J, Whitworth, James Nasmyth, J. Scott Russell, J. Anderson and Sir W.G. Armstrong. In case you think some names sound familiar, J. Whitworth is the gent that invented the Whitworth rifle and W.G. Armstrong invented the Armstrong gun and they later co-founded Armstrong, Whitworth & Co., a major armaments, shipbuilding, aircraft and engineering company. James Nasmyth is known for inventing the steam hammer, while John Scott Russell was an engineer who built the Great Eastern steamship, which was the largest ship in the world for 40 years. This superstar committee talked to General Von Lenk and presented a report in 1863 at Newcastle, with some details of the Von Lenk process which will be described below:

In the manufacture of gun-cotton, the end-goal is to produce a product that is as highly nitrated as possible. Von Lenk found that, in order to ensure the production of this, it was necessary to adopt several procedures, the most important of which were specified as:

  1. The cotton should be cleansed and perfectly dessicated (i.e. dried out) previous to its immersion in acids.
  2. The acids used should be the strongest available.
  3. The steeping of the cotton in a fresh strong mixture of acids after the first immersion and partial conversion into gun cotton.
  4. The steeping should be continued for 48 hours.
  5. The gun cotton should be thoroughly purified afterwards and every trace of free acid should be removed. This was done by washing the product in a stream of water for several weeks; subsequently a weak solution of potash could be used as a final wash, but this wasn't essential.
We will study more details about the Von Lenk process in our next post.

Tuesday, December 27, 2016

Smokeless Powders: The Invention of Gun Cotton

In today's post, we will study one of the earliest developments in smokeless powder technology: the invention of gun cotton.

In 1832, a French chemist named Henri Braconnot found that mixing nitric acid and wood fibers would produce a very explosive material. A few years later in 1838, another Frenchman, Theophile-Jules Pelouze, produced explosive materials by treating paper and cardboard with nitric acid. However, both these discoveries very highly unstable and could not be used for practical explosives. It was left to a Swiss chemist named Christian Schönbein to discover a more practical solution. The discovery of gun cotton was actually the result of an accident:

Christian Schönbein. Public domain image.

Schönbein was a professor of chemistry at the University of Basel in Switzerland. His wife laid down an order to not conduct any chemical experiments at home, but he didn't always obey her and would do his experiments at home when she was not around. One day in 1845, his wife went out for some time and he went into the kitchen and mixed up a combination of nitric acid and sulfuric acid. Due to careless handling, he spilled the mixture onto the kitchen table. He quickly grabbed his wife's cotton apron and wiped the mess up and then hung her apron over the stove to dry, so she would not find out that he'd been doing experiments at home when she was away. To his surprise, the apron suddenly ignited and burned very rapidly, leaving almost no ash behind. What he had done was accidentally create nitrocellulose (gun cotton).

Let us understand the chemistry behind what he'd accidentally invented. The manufacture of guncotton (and other nitro compounds) consists of immersing the material (cotton, wood fibers, paper etc.) in a mixture of nitric and sulfuric acids and allowing the nitric acid to act upon it for a certain amount of time. The explosive material that is formed is then separated from the acids and washed until it loses all traces of acid. For example, in the case of gun cotton, the following reaction happens:

C12H20O10 + 6HNO3 = C12H14O4(O.NO2)6 + 6H2O

The cellulose combines with the nitric acid forming nitrocellulose and water (H2O). It would appear from this above equation that only nitric acid is needed for this reaction. However, note that one of the other byproducts of this reaction is water, which would end up diluting the remaining nitric acid and cause it to form other nitro-compounds instead. This is where the sulfuric acid comes in. The sulfuric acid takes care of the water formed by this reaction and also acts as a catalyst to form the NO2 ions.

In the original version of his process, Schönbein mixed three parts of sulfuric acid to one part of nitric acid by weight. Then, he would take twenty to thirty parts of this acid mixture into a porcelain vessel and dip one part of cotton at a temperature of around 10° to 15° C for an hour. After that, the liquid was poured out and the gun cotton was thoroughly washed in water and then in a dilute potash solution to eliminate acids. It was then again washed in water to dissolve any salts formed from the previous washing, then squeezed out to remove the water, then soaked in 0.6% solution of saltpeter, squeezed out again and finally dried at 65° C. Later on, Schönbein modified this process to use 14 parts of a mixture of equal volumes of nitric and sulfuric acids, to each part of cotton.

Gun cotton produces about six times the amount of gas than the same volume of black powder, while producing far less smoke and heat.

Now that we've studied the reaction at a high level, we will look at some of the machinery used for this process in the next few posts.

Friday, December 23, 2016

Smokeless Powders: Introduction

In the last several months, we have studied the production of various forms of black powder in depth. The next series of posts will deal with an in-depth study of smokeless powders. We had studied about this some years ago, but not really in detail.

So why smokeless powder?? First, let's go over some disadvantages of black powder:

  1. It is very flammable. Black powder can easily be ignited by a single stray spark, hard impact or a hot object and therefore, it requires careful handling.
  2. It leaves a lot of residue behind, which can cause fouling problems inside the firearm. The residue is also caustic, which can cause corrosion issues if it is not removed quickly. What this means is that firearms that use black powder need to be cleaned after firing just a few shots. 
  3. Black powder also produces a lot of smoke upon ignition. In fact, many infantry troops using black powder weapons faced a problem on the battlefield in that after firing a few shots, they would no longer be able to see the enemy due to the clouds of smoke produced by their own weapons.
  4. Black powder is hygroscopic (i.e.) it absorbs water from the atmosphere. This causes two problems: the first is that presence of water makes the powder less efficient and may even spoil it to the point where it doesn't ignite reliably. The second problem is that remnants of black powder in a firearm can cause the metal to rust rapidly. Due to this, it was necessary to clean firearms thoroughly immediately after use, especially in humid areas, in order to prevent the formation of rust.
  5. Black powder does not ignite when wet. This caused many soldiers to have their firearms rendered useless during rainstorms. This is the reason why many soldiers also carried a sword or a spear as a backup weapon.
By contrast, smokeless powders offer more propulsive power than the same weight of black powder and leave a lot less smoke and residue behind. This makes it possible to not only increase the range of firearms, but also shoot for longer periods of time without cleaning the weapon -- this is what made it possible to develop semi-automatic and automatic firearms. Early smokeless powders were somewhat unstable, but as technology improved, they became a lot more stable than black powder and don't require as much careful handling. They are also not affected by rainy weather and can even ignite underwater. 

With that said, there are a few misnomers about smokeless powder that we should clear up before we go in-depth with our study. First, the name is misleading: smokeless powder is not actually 100% smokeless. There is some smoke produced, but it is much less than that produced by black powder. The second misnomer is that there is no single formula for smokeless powder. In fact, there are multiple types of smokeless powders, each made with different chemicals. This is unlike black powder, where the three ingredients are always carbon, sulfur and potassium nitrate (albeit with different proportions of the ingredients and different grain sizes).

In our next post, we will study the first development in the family of smokeless powders: guncotton.

Sunday, December 4, 2016

Black Powder - Chemical Examination

In our last few posts, we saw how people would determine the quality of black powder by measuring the physical properties of the powder, such as color, size, shape, density, hygroscopic properties etc. In today's post, we will study some of the chemical properties that people would examine to determine the quality of powder.

The first type of test was the Qualitative Examination test, which was done if the ingredients of the powder were not known (e.g. some powders did not have sulfur, others may have sodium nitrate instead of potassium nitrate, still others may have charcoal made of wood, wood pulp, bark, straw etc.).

Recall a few months ago, we had stated that black powder is a mixture and not a compound at room temperature. It only forms various chemical compounds when it starts to burn. Therefore, since it is a mixture, it retains properties of its component parts.

Therefore, to determine the kind of nitrate contained in the powder, a small quantity of powder would be put in a filter and then hot water poured over it, which dissolves the nitrate salt. The filtered liquid was then chemically analyzed to determine the type of nitrate. Next, to determine if the powder contains sulfur or not, a small quantity was placed in a beaker and carbon disulfide was poured on top and allowed to stand for a little while. The solution was then poured out and evaporated. If any sulfur was present in the powder sample, it would crystallize out. To determine the type of charcoal used, they would first remove the sulfur from the sample using the carbon disulfide solution, then they would filter it and then wash with hot water to extract the saltpeter out, then they would dry out the remaining residue and examine it under a microscope, which would show whether the carbon was made from charcoal, wood pulp, wood bark, straw etc.

Of course, the above qualitative tests would show the presence of the ingredients in the powder, but not the proportions of the ingredients. To do that, they would do quantitative analysis tests, which determine the percentages of the ingredients. To do this, they would first dry a sample of powder as much as possible. Then, they would take a known quantity of powder, run hot water through it several times to dissolve all the saltpeter and then evaporate the solution to recover the saltpeter crystals, which could then be weighed.

After the saltpeter had been removed from the sample of powder, the next was to determine the amount of sulfur in the remaining sample. This could be done either directly, or by converting the sulfur into sulfuric acid. The direct method was due to Berzilius: The sample of powder after the saltpeter was extracted, was dried and weighed and then transferred into one of the bulbs of a double bulbed tube. A current of dry hydrogen was passed over the mixture while it was gradually heated. This heat would cause the sulfur to vaporize and the sulfur fumes would be carried along with the current of hydrogen into the second bulb, where it would cool down and crystallize in the second bulb. The decrease in weight in the first bulb and the increase in weight in the second bulb could be measured and this would show the amount of sulfur in the sample. Another technique was to dissolve the sulfur in a carbon disulfide solution and then evaporate it to recover the sulfur crystals, which could then be weighed to determine the percentage of sulfur in the sample.

After the saltpeter and sulfur have been removed, the remainder was dried and weighed to determine the amount of carbon in the sample.

It is also possible to determine all the components of black powder simultaneously, using special apparatus, such as that invented by Linck in the 19th century.

Click on the images to enlarge. Public domain images.

This involves using various pieces of equipment to precisely extract the components of the powder, using carbon disulfide, hot water, barium chloride, lead acetate etc. to determine the exact quantities of the various ingredients in the sample.

Friday, November 25, 2016

Examining Black Powder Quality - III

In our last post, we studied one physical property (density) that was used by people to judge black powder quality. Today we will study another technique that people used to judge the quality of black powder: the hygroscopic properties of powder.

The term "hygroscopy" refers to the phenomenon of certain substances attracting water molecules from the surrounding air and absorbing it. Examples include table salt, sugar, honey etc. This is why they are usually kept in sealed containers, otherwise they tend to absorb water from the atmosphere and spoil.

In the case of black powder, two of its three components have hygroscopic properties: saltpeter and charcoal. The saltpeter is usually hygroscopic due to the presence of impurities such as calcium salts and sodium chloride. In general, calcium sulfates or calcium oxide can react with the sodium chloride to form calcium chloride, which is very hygroscopic in nature. The calcium chloride on the surface absorbs enough water to become a liquid and dissolves some saltpeter and the solution spreads itself through all the grains by capillary action. This causes the saltpeter to be no longer evenly distributed in the powder grains. Therefore, keeping the saltpeter as pure as possible helps keep the hygroscopic properties of the powder down.

Charcoal also influences the hygroscopic properties of black powder. As a general rule of thumb, the more charcoal that the powder contains, the more water it will tend to absorb. One more interesting factor has to do with the temperature that the charcoal is manufactured at. The lower the temperature at which it was manufactured, the more water it can absorb. As a result of this, red charcoal will generally absorb more water than black charcoal.

If the powder becomes damp, it may be restored by drying in the sun or in a dry, well-ventilated room. As a general rule, if the powder does not show an efflorescence of white crystals of saltpeter on its surface, it may be possible to dry it. Powder of smaller gravimetric density will absorb more moisture than a powder of a greater one, and a glazed powder will absorb less moisture than an unglazed one, all other things being equal. Powder that has become damp can be easily recognized by its unequal distribution of color and by the grains crushing more easily between the fingers. However, if it manages to absorb a large amount of moisture. the powder will form hard black lumps and if is reaches this state, the powder is generally useless and cannot be serviced.

To determine the moisture content of a sample of powder, a standard amount (usually 100 grains or 50 grams, depending on country) would be carefully weighed onto a glass plate. Then the glass plate would be placed in an oven and heated for a few hours at a specified temperature that depended upon the country (160 °F for England, 190 °F for Germany etc.) and then placed in a dessicator to cool for 20-30 minutes, after which they would weigh the sample again. The difference in weight is the amount of water absorbed by the powder sample.

To determine the tendency of a particular powder sample to absorb moisture, the powder sample was put alongside a sample of standard powder over a layer of water in a tub, which was closed air-tight and left for a period of time. The two powder samples would then be removed and the amount of water absorbed by each sample would be compared. This test would let people know how much their particular powder differed from the standard sample powder.

In the next few posts, we will look at some of the chemical properties that people would look at to judge powder quality.

Note: I trust my American readers had a happy Thanksgiving holiday so far. Your humble editor was temporarily hospitalized for a little while, but I recovered just in time to spend the holiday at home with family and friends, just as it should be :-).

Sunday, November 6, 2016

Examining Black Powder Quality - II

In our last post, we looked at some of the physical properties (color, grain solidity, grain size etc.) that powder manufacturers would look at, while determining if the black powder was good quality or not. In today's post, we will look at some more physical properties that they would check on.

One of the properties that they would check on was the density of the black powder. Readers may recall from their physics class that density is defined as:
        density = mass / volume
(i.e.) we take a certain amount of substance, weigh it and measure its volume and determine its density that way. Different materials have different densities, so this is a quick way to determine if the  ingredients are in proper proportion with each other. This principle was famously illustrated by Archimedes, who was tasked by the King of Syracuse in Greece, with determining if his crown was of pure gold or if the goldsmith had cheated the King by mixing some other metals with the gold. Archimedes pondered on the problem and as legend has it, he was sitting in a public bath one day and saw the water overflow as he lowered his body into the tub. Then he realized he had found a solution to the problem and jumped out of the bath and ran home naked, all the while yelling "Eureka!" (Translation: "I've found it!"). He took a lump of pure gold, weighed it carefully, and then dumped it in a tub of water and measured how much volume of water was displaced, thereby finding out the density of pure gold (mass / volume). Then he took the crown, weighed it carefully, and then dumped it in water and measured the volume of water displaced and determined its density (again, mass / volume). From the difference in densities, he determined that the goldsmith had cheated the king, not only that, he could also tell how much gold the goldsmith had stolen and replaced with cheaper metal.

Similarly, measuring the density of black powder gives a good idea of the kinds of raw ingredients used, the mixture and the presence of any impurities. As far as black powder was concerned, it is a substance with grains, therefore there were three ways to measure its density:

  1. Gravimetric density - This is the density of the powder, including the air between the powder grains.
  2. Relative density - This is the density of the powder measured excluding the air between the grains, but including the air contained in the pores of the grains,
  3. Absolute or real density - This is the density of the powder, excluding all atmospheric air.
Gravimetric density is the easiest to determine. It can be measured by weighing a quantity of powder that fills a certain space. However, due to variations in grain size and quality, this method doesn't give uniform results. Variations can also occur due to the shape of the measuring vessel, the height at which the powder is dropped into the vessel, size and shape of the grains and size of the filling hole. Therefore, comparisons of different samples are only meaningful if the same kinds of powder are measured using the same apparatus.

Apparatus to measure the gravimetric density of black powder. Public domain image.

The above apparatus was used in many European countries in the 19th century. It consists of a measuring vessel (A), made of brass or copper, which is precisely calibrated to hold exactly 1 liter (1000 cubic centimeters or 61.02 cubic inches) of material. Above it is placed a funnel B, with a conical bottom and a hole of exactly 14 millimeters (55/64 inches). The height between the bottom of the funnel and the upper edge of the measuring vessel was exactly 40 millimeters (1-37/64 inches). A cut off plate, C, was placed at the bottom of the funnel, to regulate the flow of gunpowder. To determine the gravimetric density of powder, the vessel A was first emptied and weighed very accurately. Then it was placed under the funnel and powder allowed to fall into the vessel until the grains began to run off the edge of it. Then the funnel was closed and the powder was smoothed off with a brass plate and a few light blows were struck to make the powder grains settle a little, with the excess being removed with a soft brush. The vessel was then precisely weighed again. The difference between the two weighings is the weight of the powder contained in 1 liter, from which we can find the density. Since variations in grain size could affect the results somewhat, the experiment was repeated three times and the average was taken. Depending on the type of powder, different countries had different standards for densities of powder. E.g. Germany's standards were: rifle powder must be between 0.905 and 0.925, cannon powder between 0.915 and 0.935, large grained powder between 0.960 and 0.980, Austria's standard for large-grained powder had to be between .907 and .951, Switzerland had rifle powder between 0.955 and 0.975, while cannon powder was to be between 0.960 and 0.970, French standards had musket powder between 0.830 and 0.870, sporting powders at least 0.860 etc.

To measure the relative or absolute density, people generally used quite a few methods. One of them borrows the ideas of our old friend, Archimedes. They would first take a liquid that could not dissolve any of the ingredients of gunpowder. Pure distilled alcohol was often used for this purpose. They would put a certain amount of this alcohol in a glass measuring tube, calibrated in tenths of a cubic centimeter and allow it to settle for a few minutes. Then, they would accurately weigh a certain quantity of black powder and then drop it into the tube. Due to the added powder grains, the level of alcohol in the tube would rise. They would read the markings on the tube to measure the increase in volume and since they already knew the weight of the powder added, they could now determine density = mass / volume.

This method was later improved by scientists, such as Heeren, Timmerhans, Otto and others. One of the issues was that when the powder was immediately added to the tube, the level would rise at first and then drop, as air bubbles escaped from the tube due to the alcohol seeping into the air gaps between the powder grains. Therefore, the improvements were generally procedures like waiting for a certain period of time for the alcohol level to settle, heating the alcohol and using an air pump to pull out all the trapped air in the grains etc., to get a more accurate reading.

There were also dedicated instruments called densimeters, that were developed to measure the density of black powders. Examples of these include Marchand's densimeter, Hoffmann's densimeter, Bode's densimeter, Ricq's densimeter, Bianchi's densimeter etc.

Hoffmann's densimeter. Click on the image to enlarge. Public domain image.

Bode's densimeter. Click on the image to enlarge. Public domain image.

These densimeters generally used vacuum pumps and mercury to accurately measure mass and volume of the powder grains and determine the absolute or real density of the powder.

As far as black powder was concerned, both gravimetric and real densities were measured to judge its quality. Since real density measures the density of the powder without the air in between the grains, it is possible for two powders made with the same proportion of ingredients but different grain sizes, to have the same real density and different gravimetric densities. Gravimetric density, on the other hand, depends on the size and shape of the grains, on the glazing process and percentage of dust in the powder. The gravimetric density has an influence on the rapidity of combustion, whereas the real density influences both the rate of combustion of a single grain of powder and the durability (keeping quality) of the powder during transport and use. Therefore, both densities were measured to properly judge the qualities of a powder.

Saturday, October 29, 2016

Examining Black Powder Quality - I

In the last several weeks, we have taken a detailed look at the manufacturing process for black powder. In today's post, we will look at some of the procedures that were used in the 19th century to ensure black powder quality. The procedures used examined both the physical and chemical properties of black powder. In today's post. we will look at some of the physical properties that they would look for.

In places where good quality black powder was made, the powder was examined immediately after the blending process was completed. They would also periodically take small samples from powder stored in warehouses for analysis, to make sure that it was still usable.

The first thing they would do is give it a visual inspection. The color of good quality black powder should be a uniform dark gray (or slate) color. If the color has a blue tint or is very black, then this indicates that the powder has too much charcoal or contains too much moisture. Powders made of red charcoal (such as cocoa powder) should be of brownish-black color.

A sample of good quality black powder. Click on the image to enlarge.

After this, they would examine a small sample with their eyes or through a magnifying glass. Properly mixed powder should not show any difference in color even when crushed, nor should it be possible to feel sharp particles. A variety of colors indicates that the powder was not mixed evenly and the presence of sharp particles indicates that the ingredients were not pulverized properly. Bright or bluish-white spots in the powder indicate that the saltpeter has effloresced during the drying process, which will also affect the properties of the mixture.

The powder would then be allowed to run over a sheet of paper and the paper would be examined. Properly made powder should not transfer its color to the paper. If this happens, this indicates that the powder has too much moisture or dust (meal powder).

For prismatic powders, they would check to see if the prisms have smooth surfaces and the edges are sharp and complete. They would also check to make sure that the prisms don't easily crumble or give off too much color when rubbed against a sheet of paper.

The next thing to check was the solidity of the grains of powder. Good quality powder grains should not be easily crushed by finger pressure. It should not fall into dust at once, but should break up into angular splinters. In Germany, they would put 1.1 lbs of powder in a leather bag, which was then put in a glazing drum and rotated for 15 minutes at 15 revolutions per minute. After this, they would take it out and weigh it again and the loss of weight should not be more than 1.55%. In France, they would take an average of various powder samples and dust it initially and then take 8 kg. (17.6 lbs.) of powder and put it in a barrel designed to hold 12 kg. (26.4 lbs.) of powder, which means about 1/3 of the barrel is empty space. This barrel would then be enclosed inside a second barrel and then rolled down an incline of 15 degrees for a length of 5 meters (16.4 feet). The incline was made of planks and at the bottom was a bale of hay to stop the barrel. At the side was another incline made the same way, but falling in the opposite direction. The barrel was allowed to roll down one incline, then sent back down the other incline and the process was repeated 100 times, so that the barrel would have traveled a total of 1000 meters (3300 feet). The powder was then dusted again and the remaining grains were weighed. If the powder did not lose more than 0.20% weight after this test, then it was deemed to be of good quality.

The next process was to examine the size of the grains. They would do this by taking a sample of powder (typically about 2 kg. (4.4 lbs.)) and placing it in a frame with a number of sieves in it and a tray at the bottom. The sieves would have meshes with different sized holes, with the sieve with the largest holes at the top and the sieve with the smallest holes at the bottom. They would place the powder sample on the top sieve and then shake the entire frame for a prescribed amount of time (which depended upon country) and then see how much of the powder sample was held in each sieve. There were quality standards defined for how much each sieve could hold, depending on the powder type. For instance, for good quality rifle powder, no powder must be retained in the first sieve, less than 5% in the second sieve, up to 65% in the third sieve, up to 50% in the fourth sieve and 8% at most in the fifth sieve. Similarly, for good quality cannon powder, no powder must be retained in the first sieve, not more than 5% in the second sieve and no more than 10% in the fifth sieve and all the remaining should be in the third or fourth sieve. 

In France, they would additionally also count the number of grains in a gram of powder sample to check if they were within certain limits depending on the type of powder.

In our next article, we will study some more physical properties they would study to ensure black powder quality.

Saturday, October 22, 2016

Black Powder Substitutes - II

In our last post, we looked at a common black powder substitute: pyrodex. In today's post, we will look at other black powder substitutes.

Pyrodex was one of the first successful black powder substitutes and is therefore well known, since it was first introduced in 1975. However, it still retains the sulfur smell of original black powder and produces a lot of smoke and residue and is corrosive as well, just like original black powder. Towards the beginning of the 21st century, newer powders such as Hodgdon Triple Seven (otherwise called Triple Se7en), American Pioneer Powder (originally sold as CleanShot), Shockey's Gold, Black Mag, Blackhorn 209 Goex Clear Shot and Goex Pinnacle (since discontinued) became available on the market. These powders attempted to correct the deficiencies of pyrodex and original black powder.

Hodgdon Triple Seven Powder and Pellets. Click on the image to enlarge,

Triple Seven powder is made by Hodgdon, the same people that make Pyrodex as well. It was introduced early in the 21st century and is available in both loose powder and pellet form (Hodgdon owns a patent on the cylindrical pellet). This powder is made using carbon from sources other than wood charcoal and contains no sulfur. Therefore, it lacks the typical sulfur smell of original black powder and pyrodex. Like pyrodex, it is classified as a "smokeless powder" and is therefore not subject to the strict rules and regulations that govern the storage and sale of black powder, which means many retailers are likely to sell it in their stores. It is less dense than pyrodex. Unlike pyrodex, the loose powder form is not "volume equivalent" to black powder, as it is hotter burning and about 15% more powerful. Therefore about 85 grains BY VOLUME of triple seven is equivalent to 100 grains of black powder or pyrodex BY VOLUME. The pellets, on the other hand, are formulated to be equivalent to pyrodex and black powder by volume. In addition to the lack of sulfur smell, triple seven powder is cleaner burning, produces lesser smoke, is less corrosive and easier to clean as well, as it dissolves in plain water. The one thing that some shooters complain about is that triple seven powder tends to form a "crud ring", which is a build-up of a hard crust at the location of where the bullet sits on the powder. However, a quick swab of the bore between shots can easily clean this problem. One more disadvantage is that Triple Seven powder is hygroscopic (i.e. it attracts water from the atmosphere), so it can degrade performance if not properly stored. Triple seven powder is a somewhat expensive compared to pyrodex, but is still a popular alternative.

American Pioneer Powder

American Pioneer Powder started off life as "Clean Shot". Like Triple Seven, it uses a different formulation (using ascorbic acid) that reduces the sulfur smell and is easier to clean than black powder. Clean Shot Technologies was sued by Hodgdon for infringing on the cylindrical pellet patent and went bankrupt and a new company, American Pioneer Powder, was formed, which now sells powder under the brands of American Pioneer and Shockey's Gold powder. In addition to loose powder, they also sell it in a compressed stick form, as a work-around the Hodgdon patent. Their powders are reported to clean up easier than pyrodex and triple seven, but some shooters report erratic performance.

Black Mag powders are also based on ascorbic acid and uses potassium perchlorate as the oxidizer. They sold powders under the brands Black Mag2 (equivalent to FFg grain size), Black Mag3 (equivalent to FFFg grain size) and Black Mag XP, as well as manufacturing powders for other companies, such as Alliant Black Dot. While they did have quality control issues, if properly made, it produces fairly consistent performance. It is easier to ignite, leaves less residue and far less corrosive than triple seven or pyrodex. Like triple seven, it is also a hotter burning propellant than pyrodex. Unfortunately, there was an accident at the plant that manufactures these powders in 2010 which led to safety violations charges for the owner and in 2013, he was sentenced and the plant was permanently closed. As part of the sentencing, the owner agreed never to resume manufacturing propellants or even conduct any business in the vicinity of a propellant manufacturing facility.

Blackhorn 209 was introduced by Western Powders in 2008. It is much more non-corrosive and cleaner burning than other powders. The 209 indicates that it requires a 209 shotshell primer for proper ignition. Like some of the other powders above, it is also a "volume equivalent powder" (i.e.) it can be measured using the same powder measure as black powder for identical performance. It has excellent performance and unlike most of the other powders above, it is also non-hygroscopic (which means it doesn't attract water from the atmosphere) and therefore has a longer shelf life. It also doesn't form crud or corrosion like the other substitutes and requires far less cleanup as it is low-fouling in nature.

Thursday, October 20, 2016

Black Powder Substitutes - I

A few posts earlier, we saw a mention of something called "black powder substitute". We will study more about this topic in today's post.

As we saw in several posts on the topic of black powders, it is a mixture that was used as a propellant for hundreds of years. Some of the problems with using black powder include

  1. Ignites very easily and burns rapidly, which may cause accidents if it happens unexpectedly.
  2. Produces a sulfur smell and a lot of residue after burning.
  3. It is hygroscopic and can absorb water from the atmosphere, which causes the powder to degrade.
  4. Needs careful handling and storage to prevent accidents.
  5. Is generally corrosive in nature, which means that firearms need to be cleaned thoroughly after use.
In addition to all the above reasons, black powder also burns less efficiently than modern smokeless powders, which is why most modern firearms use smokeless powders. However, there are still quite a few black powder enthusiasts, who like to use firearms (or replica firearms) that their ancestors used in the past. Due to the unsafe nature of black powder, many areas have special regulations concerning the storage, sale and use of black powder, which makes it hard for people to buy it. This is where black powder substitutes come in.

The most common black powder substitute in use today is called "Pyrodex", which was invented by the Hodgdon Powder Company in 1975.

Pyrodex Powder. Click on the image to enlarge. Public domain image. 

Ordinary black powder can easily be ignited by impact forces, sparks or static electricity, which makes manufacturing and storing it more dangerous. In fact, the last factory manufacturing ordinary black powder in the US was closed in 1970 after an accidental explosion and new regulations came out that made many retailers reluctant to sell black powder any more. In 1975, the Hodgdon Powder Company invented the first black powder substitute: pyrodex.

Ordinary black powder consists of  just saltpeter (potassium nitrate), sulfur and charcoal (carbon). Pyrodex also has these three ingredients, but also contains graphite, potassium perchlorate and some other proprietary ingredients. These additional ingredients make the properties of pyrodex behave more like a smokeless powder and therefore, it is not subject to the same strict regulations of black powder. This means that pyrodex doesn't ignite as easily as black powder and can be stored and transported just like a smokeless powder, which is why many retailers sell it.

Pyrodex is actually about 27.5% less dense than ordinary black powder and is more efficient than it. So how does the substitution work then? Well, when measuring ordinary black powder for muzzleloading weapons, people have always specified powder loads by weight (e.g. grains in the US, grams in most other countries), but they have usually measured it out by volume. What this means is that if a muzzleloading rifle takes (say) 100 grains of black powder as a load, the user doesn't usually actually weigh out 100 grains of powder to load into the rifle. Instead the user has a powder measuring tube, which he (or she) fills with black powder and pours that into the rifle. If the user measures the weight of the black powder from the measuring tube, it will indeed weigh 100 grains (or something close to it). When using pyrodex, the user can use the same measuring tube to measure out a quantity of pyrodex. If the user weighs the contents of the measuring tube, it will weigh around 72.5 grains, since pyrodex is less dense than black powder. However, this 72.5 grains of pyrodex burns with about the same propulsive force as 100 grains of black powder, since pyrodex is a more efficient propellant. Therefore, if the user uses the same measuring tube to measure black powder or pyrodex, one can easily be substituted for the other, without affecting the pressures generated in the rifle. This makes pyrodex a "volume equivalent powder". 

It must be remembered that muzzleloading weapons are commonly loaded by volume using measuring tubes, this works out great when using a volume equivalent powder like pyrodex. However, black powder cartridges are loaded by weight. Therefore, if using pyrodex instead of black powder to load a cartridge, the user must actually load a lesser weight of pyrodex to retain the same amount of propulsive force. 

Pyrodex powder has a similar burning sulfur smell as black powder and is also very corrosive in nature and produces about the same amount of fouling as ordinary black powder. Therefore, users need to perform the same cleaning procedures as when using normal black powder. However, since pyrodex is less susceptible to ignition, it is subject to the same regulations as smokeless powder, instead of the the much stricter regulations of black powder. 

Pyrodex is normally sold in a few grain sizes: Pyrodex RS (Rifle/Shotgun), which is volume equivalent to FFg grain size black powder, and Pyrodex P (Pistol) powder, which is volume equivalent to FFFg grain size black powder. There is also Pyrodex "Select" powder, which is the largest grain size of all and is marketed as an "extremely consistent" grade of pyrodex, meant for muzzleloading rifles. 63.9 grains of Pyrodex "Select" powder have the same volume as 100 grains of black powder.

These days, pyrodex is also sold in pellet form, such as the image below:

Pyrodex pellets. Click on the image to enlarge. 

With this type of pyrodex, the user doesn't have to use a measuring tube to measure out the powder, since the pellets are all of a certain specific size. Instead the user simply takes a pellet or two and loads it directly into the firearm.   

We will study more about black powder substitutes in the next few posts.

Sunday, October 2, 2016

Black Powder Factories - II

In our last post, we studied how early gunpowder factories were often located in the middle of towns in the early days of firearms. Of course, placing a factory within your town walls made sense if you wanted to defend your town walls against attack, but there was the problem of accidents in the factory setting the town on fire. Towards the beginning of the nineteenth century, people began to think more about factory safety and several laws were passed specifying how far away a gunpowder factory could be away from people's houses and how much powder could be worked inside one building and so on. In today's post, we will study how one such factory was set up in the 1860s. Today's object of study will be the Confederate Powder Works.

A view of the remaining chimney of the Confederate Powder Works in Augusta, Georgia
Click on the image to enlarge.

Not much remains of the Confederate Powder Works these days, except for one 150-foot tall chimney, but in its day, it was a massive factory complex laid out over two miles in length and was the second largest gunpowder factory in the world then.

During the days leading up to the Civil War, the Confederate states did not have any significant gunpowder manufacturing facilties, except for a small mill in Tennessee. On July 10th, 1861, Confederate President Jefferson Davis authorized Major George Washington Rains to build whatever was necessary to keep the Confederate armies supplied with gunpowder.

Colonel George.W. Rains. Click on the image to enlarge.
This photograph was taken during the Civil War and is currently in the Augusta Museum of History.

Major Rains spent the next few days living in a railroad car, examining various places for a suitable location for a factory. On July 20th, he selected an area in Augusta, Georgia to be the site of the future factory. The reasons for picking this area for the new factory were several:

  1. It was centrally located and near the junction of some major railroads.
  2. The area was near enough to a big town (Augusta) to provide sufficient workers and materials.
  3. It was far enough from the front-lines that Union forces could not easily attack it.
  4. The Augusta canal and the Savannah river could also be used to transport over water.
  5. The Augusta canal was also a source of water power, which is useful to drive factory machinery.
  6. The area has temperate weather, which means the water supply does not generally freeze during the winter months, thereby ensuring unlimited water power during the whole year.
  7. Since he also intended to produce pure potassium nitrate (saltpeter) in the factory, he also needed abundance of water to wash and refine the minerals.
  8. The canal could also be used to transport supplies and materials from one factory building to the next. 
However, Rains had a few big problems: First, he had no idea about how to build a gunpowder factory, having never been inside one before! Luckily, he came across a book authored by a Major Fraser Baddeley of the Royal Artillery in England, called "Manufacture of Gunpowder as carried out at the Government Factory, Waltham Abbey", that described the entire process and machinery used by the Royal Gunpowder Factory at the Waltham Abbey works in Essex, England. While the book had the descriptions, there were no drawings or plans of the buildings or machines, therefore he had to research on his own to figure these out. Luckily for him, he happened to find an Englishman named Frederick Wright, who had moved to the Southern states and had worked at Waltham Abbey previously, so he asked him for assistance and produced some detailed word descriptions and preliminary sketches. 

The next problem was to find an experienced architect to build the plant while he was occupied with other duties for supplying the existing armies in the field. He hired a couple of young civil engineers/architects, Miller Grant and Charles Shaler Smith to do the job. Construction of the first building started in September 1861. By the time the factory was in full operation, 26 separate buildings were constructed over 140 acres of land that extended almost two miles along the banks of the canal.

The buildings were constructed along the canal, coinciding with the process of making black powder (i.e.) the warehouses to store the raw materials were located first in line, the refinery to refine saltpeter was next and so on, until the final building at the end of the complex, which was used to store the finished gunpowder. The canal was used to transport materials from one building to the next, much like a modern assembly line. The most important buildings were built first: the Refinery, the Incorporating mills, the Mixing house, the Granulating house, the Pressing house and the Drying house and the Boiler house. Other buildings include a blacksmith's house, the stables, a carriage house, a laboratory etc. We will discuss the construction and use of these buildings in the next post or two. The refinery building in particular, was very beautiful to look at, being constructed in a Gothic revival style, influenced by the Smithsonian Institution in Washington DC and the British Houses of Parliament. The chimney in front of the refinery was shaped like an obelisk and is the only structure that survives today, located at 1717 Goodrich Street in Augusta. The buildings were separated from each other and designed to survive explosions, in accordance with the safety procedures used in other gunpowder factories in the 19th century.

The first gunpowder in the factory was made on April 13th, 1862; just nine months after Rains had been authorized to build the factory and construction of new buildings continued as the factory expanded. The factory remained in operation until the surrender of the South during the end of April 1865, which means it remained in operation for a little over three years. During this time, it managed to produce approximately 2,750,000 pounds of gunpowder at an average rate of around 7,000 pounds a day. In addition to this, the factory also produced other war material, such as time fuses, artillery pieces, wagons etc. Due to his efforts in building the factory, Major Rains was promoted to a full colonel by the end of the war.

After the Civil war ended, the factory fell into ruin. In 1872, a project to widen the Augusta canal resulted in most of the buildings to be destroyed, leaving only the tall chimney that can still be seen today. The chimney was spared, at the request of Colonel Rains, as a memorial to those who died in the Southern armies during the Civil war.

A view of the chimney as it exists today, courtesy the Augusta Historical Society.
Click on the image to enlarge. 

In 1880, a new mill was constructed in the old powder works area, called the Sibley cotton mill owned by the Sibley family. Bricks from the demolished buildings were used to construct the new mill and it was built with the appearance of a medieval castle or fortress, similar to the powder works buildings that it replaced.  The cotton mill was very successful and remained in operation until around 2006, making denim cloth for major clothing manufacturers. While the mill production has ended, the water-driven turbines still remain in operation and generate electricity that is sold to Georgia Power even today. 

Monday, September 26, 2016

Black Powder Factories - I

In the previous several posts, we have studied several aspects of black powder manufacturing. But what about the factories themselves? In the next few posts, we will study the layouts and processes used in the factories.

Curious though it may seem, even though people knew that black powder was potentially explosive from the earliest days, it was made for a considerable time within towns, probably because towns were often under siege and needed the factory to be inside to supply the gunpowder for the guns mounted on the town walls. Of course, there were accidents: For instance, in 1360, it is recorded that the town-hall of Lubeck, one of the largest and richest cities in the Hanseatic league (now in Northern Germany) was burned to the ground, thanks to the carelessness of the gunpowder makers of that town. In 1528, the town leaders of Breslau finally issued a law prohibiting manufacturing gunpowder within the town. In 1490, Venice passed a law to move gunpowder manufacture from the city center to the Venetian Arsenal (which was not in the city center, but pretty darn close to it), but many of its other factories (such as in Padua, Treviso, Verona, Brescia etc.) were located practically at the center of town. It took a major fire at the Venetian Arsenal in 1569, which forced the Council of Ten to pass a law to make both gunpowder manufacturing and storage outside the urban area of Venice. The new site was the small island of Sant'Angelo di Concordia (later renamed to Sant'Angelo della Polvere because of the gunpowder factory), which was located to the south-west of the main islands of Venice.

The Island of Sant'Angelo della Polvere in the Venetian lagoon.
Click on the image to enlarge. Image is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license by Maurice Ohana

However, Venice was more of an anomaly because it had a strong navy and didn't need city walls because of protection by the sea. Most towns still continued to locate their gunpowder factories within their walls. And if the factories were located outside the heavily populated areas, the buildings were often located haphazardly.

It was only in the nineteenth century that regulations governing factory safety went into place in many countries. Laws were passed specifying the distance of the factory buildings from citizens' houses and from each other and also how much quantity of ingredients or powder may be worked on at a time in each building, materials to be used to construct the buildings and so on.

Since powder factories need a considerable amount of machinery to pulverize, mix and combine powder ingredients, they were generally erected in places where a large amount of water power is available, such as a fast flowing river or canal. In places where water power could not be reasonably applied, animal power (e.g. oxen, horses etc.) was used instead. For instance, we know that horses were used in Venice because various records of purchases of horses and hay for the Venetian powder factories from 1560-1570 have survived. Later on, when the steam engine was perfected in the 1760s by James Watt (although it was invented and worked on by other people many years before, James Watt made it much more practical for factory use), some gunpowder factories began to use steam power to drive their machinery, which made it possible to locate the factory away from flowing water.

Where water power was used, the machinery required for a particular operation were arranged in pairs, so that there would be one machine on the left side and the other on the right side. The water wheel would be located at the center, or individual wheels would be placed on each side and the water routed via canals to either side. Power would be transmitted from the wheel to the machine using gears and gear shafts. In some cases, a large water wheel would transmit its power to various buildings using wire ropes and chain arrangements.

Animal power was used where water power was not readily available, but the machines in these factories were smaller. Running costs were higher because not only did the machines require repairs and greasing, but the factory also had to pay for the animals, their food, their stables and the people who were caring for those animals.

When steam power was used, there were two methods to transmit the power. The first method consisted of installing a large steam engine located centrally, which produced all the power required and this was transmitted to the various buildings using wire ropes. In this case, the steam engine was located in a central building and the other buildings were arranged in a circle around it, as was done in France in the factory at Sevran-Livry in Paris. The other option was that steam was produced in a large boiler plant and the steam was transported via an arrangement of pipes into the various buildings, where it was fed into smaller steam engines. With this method, the fire that produced the steam was kept away from the buildings containing the steam engines.

Water wheels are somewhat low in efficiency compared to other types of power, but they are very cheap to build and running costs are very low, with only application of grease and repairs to be done periodically, the water (which is the source of power) generally costing nothing. The technology of water wheels was well understood for many centuries, being used by the Egyptians, Greeks, Romans, Chinese, Indians, Arabs, Medieval Europe etc. The only thing to watch out for is floods and droughts, which could either wreck the factory or cause it to stop functioning. However, because of the low costs, water wheels were used anywhere that water power was readily available, and were competitive with steam engines well into the Industrial revolution.

Steam engines are higher in efficiency compared to water power and could be used as long as there was an adequate supply of fuel and water. Transmitting the power from a central engine to various buildings via wire ropes was fine over shorter distances, however the power losses can be considerable over larger distances. There is also much more lubrication needed for the ropes and pulleys and in case a rope breaks, a whole section of a factory could stop functioning. Therefore, many factories got around this by using a system of insulated pipes to transmit the steam to smaller steam engines located inside each building. Of course, the pipes had to be checked to ensure that they were not leaking steam and over-pressurization could cause pipes to break and stop work immediately, but using a system of smaller pipes and valves solved this issue somewhat because the valve of one pipe could be shut down for maintenance, while another parallel pipe or two could continue to carry steam to the machine while the first pipe was being examined and repaired and so on.

Thursday, September 22, 2016

Brown or Cocoa Powder

In the last several posts, we've studied about the development of black powder. In today's post, we will study another type of powder that was briefly used in the 19th century, which was called brown powder or cocoa powder on account of its color.

The purpose of cocoa powder was to make a powder that would burn at a slower rate than black powder, for use in large artillery guns and ship cannons. It was similar to black powder, but it could be used in larger guns than what black prismatic powder was used for.

Around 1880, a company called Rottweil Pulverfabrik (translation: "Rottweil Powder Factory") from the town of Rottweil, Germany invented a new form of powder that used a different type of charcoal that was reddish-brown in color. In case readers are wondering, yes, Rottweil is also the town where the Rottweiler breed of dog was developed.

View over a part of the Rottweil Powder Factory in 2014.
Click on the image to enlarge. Image licensed under the Creative Commons Share-Alike Attribution Version 3.0 license by Andreas Koenig.

This powder had a different composition than black powder, consisting of 79% niter, 3% sulfur and 18% charcoal (whereas most black powders of that era were around 75% niter, 10% sulfur and 15% charcoal) and also contained about 1-2% moisture. The charcoal for this powder was also made in a different manner. We've studied how charcoal was manufactured for black powder earlier. Brown or red charcoal is a charcoal that is made by under-burning organic material. The material used for producing this charcoal was rye straw. The straw was piled into large stacks and stored in open air for long periods of time, the stalks being large and thick, with the ears of rye removed from it. Then, the straw was placed in large wrought-iron chambers and superheated steam was pumped over the straw for several hours. The temperature of the superheated steam was carefully controlled. The superheated steam would dissolve most of the extractive matter from the straw, but would not char it fully and the result was a charcoal of a reddish or brown color (in French, this was called charbon roux). We studied about this charcoal production process using steam earlier.

These ingredients were then mixed together and compressed into hexagonal prisms with a central hole, using the production methods used for prismatic powder that we studied earlier. This brown powder burned at a slower rate than black powder, and for equal muzzle velocities of the projectile, it produced less pressures inside the bore of the gun than black powder, and also produced less smoke than black powder as well. The more gradual development of pressure and reduction of the maximum pressure produced increased the life of the barrel and made it possible to develop lighter cannon.

The Germans adopted cocoa powder for their military in 1880. In 1884, the British Royal Navy decided to use cocoa powder for their ship guns and they bought their supplies from Rottweil Pulverfabrik. Soon after this, the French Navy also started using cocoa powder, but they developed their own version called Slow Burning Cocoa (SBC) powder around 1887. It was so successful for use in larger guns that it was sought by other militaries around the world as well. In England, they began to substitute charcoal made from rye straw with red charcoal made from wood and carbohydrates (such as sugar), to keep up with demand.

However, this powder did not burn all that cleanly (one test showed that about 43% of the powder was burned, the remainder formed large clouds of smoke) and it also left deposits in the bore. Therefore, when smokeless powders, such as the French Poudre B and the British Cordite powder were developed, brown powders became obsolete shortly after.

Saturday, September 17, 2016

Black Powder XXV - Pellet Powder

In our last few posts, we saw some developments in compressed black powder technology, prismatic powders and pebble powders. In today's post, we will study another type of compressed powder called pellet powder, which was invented in the 19th century.

Pellet powder was a large grain powder designed to be used in larger guns. In our above example, each pellet is a formed cylinder of black powder about 1.25 inches in diameter with a hole in the center.

Sir John Anderson of Woolwich arsenal in England invented a machine in the 19th century for their manufacture, the details of which are below:

A machine for making pellet powder invented by Sir John Anderson. Click on the image to enlarge. Public domain image.

It consists of a disk of about 6 feet diameter (the pressing table) which revolves about one of the columns. The disk has teeth all around its circumference, which allows it to be rotated by means of a pinion and handle mechanism. The disk has four round metal plates placed symmetrically, about 2 inches thick and 1.5 feet in diameter. In each metal plate are drilled about 200 cylindrical holes of about 5/8 inch diameter. Above each plate is a movable covering-plate which can be pressed tightly against it, and into each of these 200 holes a small plunger enters, which goes through the bottom part of the disk and can be lifted from below by a hydraulic press.

Two opposite plates are always pressed at the same time. As soon as the movable plates are lifted, the molds are filled with meal powder, the plates are cleaned and excess powder wiped off, and the movable plates lowered and fixed so that they close the holes on the top. Then the plungers are pressed into the molds, causing the layer of powder to be compressed to 5/8 inches in height. After this, the movable plates are lifted and the plungers are pushed further into the holes, thereby pushing the formed pellets out of the mold holes.

Click on the image to enlarge. Public domain image.

After the pellets are pushed out, the disk is then rotated for a quarter turn and the pellets are taken off the two mold-plates. Meanwhile the same operation is then carried out with the other two plates.

The pressure applied to the powder by this machine is about 0.5 tons per square inch. The pellet formed is shaped like a cylinder with one or both bases having a hollow in the middle in the shape of a blunt cone. The size of the pellets made by this machine are 5/8 inch diameter, 5/8 inch height and depth of the hole is 1/4 inch and each pellet weighs about 100 grains.

In America, the Du Pont powder company made a hexagonal pressed pellet powder, which looks like two truncated hexagonal pyramids connected by a cylindrical layer of powder.

Du Pont Powder. Public domain image.

This powder was made by the following process: A lower plate in which a number of pyramidal holes were cut was covered with powder and a second similar plate was laid over it and then pressure was applied. Depending on the thickness of the layer of powder, the cylindrical part connecting the two pyramidal halves will be thicker or thinner. After pressing, the cake is broken, this causing the grains to break off on the edges of the cylindrical part.

In Italy, they made compressed pellets in cubical form, sold under the brand name "Fossano Powder", because it was first manufactured in a gunpowder factory at the town of Fossano in northern Italy. Fossano powder is a type of "Progressive Powder" and was invented by Colonel Quaglia (the factory director) and his assistant, Captain de Maria.

Fossano Powder. Public domain image.

The manufacture of Fossano powder was done in multiple stages. In the beginning stage, meal powder was pressed into cakes of density about 1.79. Each cake was then broken up into irregular grains of about 1/8 to 1/4 inch in thickness. Then grains were then mixed again with a certain quantity of meal powder and then pressed into cakes again, with a density of 1.776. This second cake was then broken up into cubes. Therefore, each cube would be composed of powder pieces of higher density enclosed in a powder material of lower density, sort of like raisins inside a plum-pudding. The idea behind this was that due to the differing densities of powder, more gas would be produced after the powder has been partially burnt, than at the start of ignition of the powder, leading to the 'progressiveness' of the explosion (which is why it is called a "progressive powder"). This allows the pressure on the projectile to be maintained during its course in the bore and possibly increased while it is moving away.

Pellet powders burn slower than other ordinary large grained powders due to their larger grain sizes and is therefore less violent in action. Experiments in England showed that these could produce muzzle velocity greater than ordinary large-grained powder with peak pressure hitting about half that of large-grained powder.

Pellets are still available today for black powder enthusiasts:

Pyrodex 50/50 grain pellets/

Click on the image to enlarge.

Click on the image to enlarge

The above images show modern pellets available today in many sporting goods stores. However, these are made of black powder substitute, not original black powder. Black powder substitute is less sensitive to ignition than real black powder and is more energetic.

Saturday, September 10, 2016

Black Powder XXIV - Pebble Powders

A couple of posts ago, we saw why larger grain black powders were more suitable for larger guns and artillery, and studied two powders that were developed to handle this: compressed powder and prismatic powder. In today's post, we will study another type of black powder designed for larger calibers, which was in use in the 19th century. Today's object of study will be pebble powders.

Pebble powders were generally made in two grades: the P type (which were cubes of approximately 1/2 to 5/8 inches in size) and the P2 type (which were 1.5 inch cubes).

The process of manufacturing pebble powders started off similar to manufacturing other finer grain powders, until the process of pressing the powder into cakes. The pressed cakes were formed into slabs of about 15 inches x 30 inches and thickness depending on whether P type or P2 type was being made (i.e. 1/2, 5/8 or 1.5 inches).

For P type powders, the pressed cake slabs were then fed into a cutting machine:

A cutting machine for manufacturing P type pebble powders. Click on the image to enlarge. Public domain image.

The exploded view of the machine above was invented by a Major Morgan and was in use at the Royal Gunpowder Mill in Waltham Abbey, England. It consists of two pairs of phosphor-bronze rollers which are at right angles to each other and at different heights. Each roller has knives attached to its circumference, with spaces between the knives corresponding to the required size of the powder cubes. The pressed cake enters the first pair of rollers and is cut into long thin strips and these strips then fall on to a conveyor belt which carries them to the second pair of rollers, which are at right angles to the first pair. The second pair of rollers cut the long strips into cubes.

It may be seen that if a first pair of rollers were fixed, then the second long strip cut would fall onto the first and the third one on to the second and so on and the result would be long strips piling up in one location on the lower conveyor belt. To avoid this, the upper pair of rollers are mounted on a board which is arranged to move back and forth, the basic mechanism of which is shown below.

The bottom of the board has a fixed slotted bar. The chain has a pin on one of its links that engages the slotted bar. As the chain moves along its two rollers, it pulls the board above it in a back and forth motion. This results in the long strips cut from the first set of rollers falling side by side instead of one above the other.

For P2 type powders, the cubes were generally cut by hand, by using lever-knives (i.e.) knives hinged at one end, with an handle at the other, much like a modern day paper trimmer. The press cakes were cut into long strips and then cut across into cubes.

After this, both P and P2 type powders were sent through a glazing and dusting process, to ensure that edges and corners of the cubes were rounded off and sharp edges removed. This ensured that the cubes would have a harder surface and would not produce dust or waste when being stored or transported around.

The powder was then dried similar to the process of drying the smaller grain powders, except that the temperature of drying was lower and the drying period was correspondingly longer. The drying process was slower to avoid forming cracks on the cubes. After this, a finishing process followed, with the powder being run in wooden barrels, which combined sifting the powder along with a finish glaze. A small quantity of graphite powder was introduced into the finishing barrels to give the grains a glossy finish and render them less hygroscopic.

In our next post, we will look at pellet powders.