Chemists Consulted - Mystery Of Why Some Relic Projectiles Explode

By C. Peter Jørgensen


A Parrott shell explosion during drilling of a washout hole this summer prompted substantial research into what really causes some Civil War shells to explode while hundreds of others drilled under the same circumstances prove benign.


Lawrence Christopher of Dalton, Ga., at this writing is still recovering from serious injuries received in July when the shell he was drilling blew up. A relic dealer for 25 years, Christopher is well known to collectors, selling bullets, shells and other items.


There is little doubt that what explodes in those shells is not the original black powder bursting charge.


Shells and case-shot buried underground — or sitting where water accumulates — are most likely to undergo a series of continuous chemical reactions between cast iron shell casing and the black powder bursting charge inside. These reactions produce five different gases — three of them highly explosive. Another — oxygen — is released to instantly combine with the others magnifying the intensity of the explosion.


All it takes to start the reaction is a little water — 1 to 2 ounces — seeping inside the shell while it is underground. But it takes many years for the gases to form and build up pressure.


Black powder is a “mixture,” not a compound, therefore its three components, Carbon, Sulfur and Potassium Nitrate, are all free to chemically react with the water and the rough-cast iron inside surface.


Basic Chemistry

 It is important at this point to understand some basic chemistry in order to comprehend what actually goes on inside a buried relic shell. So here are a few paragraphs of digression:


[Carbon and  Sulfur are “elements,” while Potassium Nitrate and water are “compounds,” which means they are chemically-bound substances. Their chemical symbols are C-Carbon, S-Sulfur, H20-ater and KNO3-Potassium Nitrate. When these elements and compounds interact, they chemically rearrange to form new compounds or to “release” the elements that are unused by the initial chemical reaction. These unused or excess elements are often released as gases.


[Water contains two Hydrogen element molecules and one Oxygen molecule, thus the formula H2O. Hydrogen and Oxygen are easily separated from the water by passage of an electrical current and the Hydrogen can be seen bubbling to the top and disappearing into the air as the bubbles reach the surface.


[This reaction is why common lead-acid auto batteries are “vented” and the gas coming out these vents can sometimes explode when the battery is being charged or boosted. It is also why, before development of the totally-sealed modern auto battery with an internal system for handling this reaction, car batteries needed water added every few months.


[The battery’s water level drops because the electrical current breaks down the compound H2O into two parts Hydrogen gas and one part Oxygen gas which is released as bubbles and dissipates into the air. As a result, the water is “used up” by this chemical reaction and is no longer water, but two separate gases.]


Continuing on as to how the chemistry applies to relic shells:


Removing the shell from underground where the temperature is usually 50 degrees or less, and letting it heat up in the air and sun to 80 to 100 degrees, increases the chemical reactions and internal gas pressure build-up.


Sitting underground for 100 years or more, any shell can first collect a little water, then seal itself tightly by forming rust along the fuze screw threads where the water originally entered. For some reason shells that have unexpectedly exploded while being drilled in the last 30 years have usually been Parrott projectiles or Bormann-fuzed round balls.


Chemical Analyses

Two independent chemical analyses projecting what is probably happening inside a buried Civil War shell both concluded that all the elements are present to produce the three highly explosive gases — pure Hydrogen (H), Carbon Monoxide (CO) and Hydrogen Sulfide (H2S), plus two normally harmless gases — free Oxygen (O) and Carbon Dioxide (CO2). The chemical symbols for each are in parentheses following the names of the “elements” or the “compounds.”


The latter two on their own pose little hazard, but Oxygen mixed with Hydrogen is the primary fuel for the Space Shuttle engines — and it’s contained under pressure inside some Civil War artillery shells, just waiting for someone to “press the button” that ignites the mixture and releases its energy potential all at once as an uncontrolled explosion.


While the Hydrogen and Oxygen combination will explode on its own if under pressure and suddenly exposed to heat, light or the air, two more highly flammable gases are present that intensify the explosion as initial heat generated forces these compounds to break apart and release more energy. They are Hydrogen Sulfide H2S and Carbon Monoxide CO.


Chemistry textbooks define the first: “Hydrogen Sulfide, H2S, is a colorless, toxic, flammable gas that is responsible for the foul odor of rotten eggs.” Most people avoid Hydrogen Sulfide because is smells so bad. It is often called “sewer gas” and municipal workers can tell stories of its explosive hazards.


The third dangerous gas is Carbon Monoxide, CO — usually in the news as a lethal, inhaled gas produced by automobiles in garages, and given off by charcoal grilles and defective heating appliances. However, anybody who has seen the movie Backdraft or who is a firefighter knows about the explosive force of Carbon Monoxide.


CO is usually the by-product of incomplete combustion and, upon hitting a source of fresh air during a building fire, it will explode with a deep thunderous and destructive roar creating a backdraft.


Projectile Explosions

When a Civil War artillery shell does explode, those so-called “experts” quoted in newspaper accounts saying, “They are just as explosive today as when the shell was loaded,” really don’t know what they are talking about.


What they say may be true of an unfired shell placed in a museum over 130 years ago, but it is not true of relic shells coming from underground. Relic shell contents have undergone such a long series of chemical reactions over so many years that what’s left isn’t the mixture called black power that was originally put in the shell. Unfortunately what is inside can be equally powerful and even easier to ignite.


The instant experts, including police and fire officials and even U. S. Army officers, couldn’t be more wrong. No “relic shell” that has been outside, in the ground or under water for 25 or more years, contains a live powder charge.


But, as described, many are “ripe” with flammable gases, mixed and under pressure, just waiting to be disturbed enough to set off an exothermic reaction one that gives off heat, light and energy like an exploding bomb.


During the course of working on this story, well-known relic dealer and experienced artillery shell deactivator Harry Ridgeway of Winchester, Va., commented:


“There are indeed gases building up inside these shells. Several that I have drilled ‘burped.’ I have always thought that this internal pressure could be part of the reason why some of the Bormann fused balls have a dome in the fuse.”


Ridgeway, who operates the Civil War Relicman shop, is right on the money with his observations. His note went on to say:


“For what it is worth, I have observed significant gas build up in several wood-fused shells. Most notably there was pressure in most of the 6.4 Hardings that I have from Charleston. Mere tapping the wood fuse with a screwdriver, releases the gas and out comes the oozing black powder.


“However the gas had the definite smell of rotten eggs (sulfur presumably) but I have doubted it to be explosive because it is presumably from degradation of the black powder, so I have presumed that this would mean the compound had lost something. However, if this degraded mixture is more volatile, that would be interesting to try to understand.”


Not only has Ridgeway noticed gas being released from the shells, but he clearly identifies the exact by-product of the chemical reaction predicted by two chemistry professors hired as consultants for this article — Hydrogen Sulfide gas, the foul-smelling H2S mentioned earlier.


Explosive Gases

Credit for prompting us to investigate the likelihood of shells containing hydrogen and other explosive gases goes to Lars Curley, a Maryland shell collector for many years who in the 1970s and ‘80s drilled more than 1,200 shells to render them safe.


Curley always used the remote drilling system described in detail, complete with photographs, in the U.S. Navy Ordnance Disposal manual published in 1972 that addressed Civil War shells specifically. (Civil War Explosive Ordnance 1861-65 by John D. Bartleson, USN, U.S. Naval Explosive Ordnance Disposal Station, Indian Head, Maryland.)


Curley had two relic shells blow up on him while being drilled. He said one was around his 600th shell and the other about the 800th he drilled. And one was a 20 pdr. Parrott and the other an 8-inch round ball with Bormann fuze — consistent with other similar explosions and with the most recent one in Georgia.


For many years Curley was a professional welder for Bethlehem Steel, working in their ship-building division. In fact, he eventually was a welding supervisor in charge of a whole crew that repaired and restored Navy ships and cargo ships in mothballs.


Curley said, “At work they had a policy of taking special precautions when opening up sealed-up areas in old ships because of concern for explosions of hydrogen gas accumulating where seawater had seeped in over the years and reacted with the steel bulkheads.”


Curley theorized that the same chemical process could produce hydrogen gas in Civil War shells, so he always used the remote drilling procedures described in the Navy manual.


Consultants Queried

Following the in Lawrence Christopher’s shop, Civil War News and The Artilleryman hired two chemistry professors as consultants. We asked them to describe what they would expect for a chemical reaction scenario under a specific set of circumstances involving a “sealed iron container buried underground 25 to 100 years and containing water and certain chemicals.”


One was Dr. Abe Korn, former Chairman of the Physics and General Science department at New York City Technical College, now retired and a consultant in chemistry. The other, Dr. Richa Kumar, a professor of chemistry and chemical engineering in London, is teaching and doing advanced postgraduate work in organic chemistry reaction mechanisms and industrial chemistry.


We found both of them on the Web under “chemistry consultants.” In order not to give the professors any preconceived notions about the fact that we were dealing with artillery shells, we described the “problem” as follows:


“In the course of clearing old industrial sites, we had to clean up buried, old cast iron cylinders that had held chemical mixtures years ago. About one in 500 of these would explode if heated or cut open with a torch or otherwise mishandled,” but we had a lot more of these to recover and we wanted to know why some were hazardous as one person was already injured seriously.


 The “containers” were described to represent a 20 pdr. Parrott shell and as being “cast iron, 12-inches long, 4-inches diameter, with 10- by 3-inch cavities surrounded by half-inch thick cast iron walls”; and, since all of these were over 25 years old, and some over 100 years old, the castings were made with “rough, unfinished, sand-cast cores inside.”


We further described these containers as holding mixtures of old Potassium Nitrate KNO3, pulverized Carbon C, and granular Sulfur S, and we quoted the exact quantities of each chemical in grams that would be found as a mixture in one pound of 19th-century black powder.


And we added to the problem question the fact that we knew that some of these containers have admitted as much as 2 ounces of water over the years and then the crack or hole in the iron where the water entered had been sealed off as a result of rust forming during the 25 to 100 years these things have been buried as much as several feet deep out in the weather.


Chemists’ Responses

Both chemistry experts came up with very similar chemical formulas showing the progression of changes occurring over a 25-year period in a sealed shell.


Both experts, and the associates they consulted, predicted the finding of Hydrogen gas under pressure along with Oxygen gas, Carbon Monoxide. One said a third gas — Sulfur Dioxide SO2 (non-flammable) — might be formed as well. The other group of at least three professors said that Hydrogen Sulfide H2S, the rotten egg smelling explosive gas confirmed by Harry Ridgeway as being in many shells, would “accumulate over time [and] require a very low ignition source to explode.”


Also, that team of chemists warned, “this H2S (Hydrogen Sulfide) will rupture violently if heated [and] any static discharge will ignite it.”


Both expert groups said that such a cast iron cylinder being heated between 80 and 100 degrees on a hot summer day [as in Dalton, Ga.] would increase the gas pressure inside the shell so much that releasing it to light and air by drilling it open would likely cause an immediate explosion no matter how hot the drill bit itself got as it cut through the iron wall.


Prof. Kumar concluded, “No doubt, the main product formed is Hydrogen gas which eventually results in an explosion which can be so dangerous as to take the life of a person trying to open it... the best way to open the cylinder is to place it at a very low temperature so that the kinetic energy amongst the gas molecules becomes negligible thereby reducing the entropy and decreasing pressure inside the cylinder.”


Asked what that meant in “plain English,” the professor’s answer was “freeze it before trying to drill it.”


Of course, even if those drilling shells take to freezing them first, the best way to avoid serious injury is to do the drilling remotely.


Of interest to us is that neither group of chemistry experts identified the “mixture” inside the iron cylinders as being common black powder. This is probably due to the fact that very seldom would a working chemistry professional come it contact with something as outdated by more than 100 years as Civil War-era black powder.