Stevens Institute of Technology: Stevens Student Recreates and Tests Medieval Gunpowder

Early alchemy concerned itself with finding the elixir to everlasting life and transforming common materials into precious metals such as gold. But along the way, they accidentally created gunpowder, possibly one of the most consequential inventions in human kind, while also setting the foundations for a more exacting science, modern chemistry.

In a dual move that straddles how early alchemists experimented with explosives and contemporary science’s need for evidence-based reasoning, Kathleen Riegner, 21, a chemical engineering senior at Stevens Institute of Technology, spent her summer in 2020 recreating gunpowder recipes from the Middle Ages and testing them on a replica cannon on a gun range in West Point.

Three people firing a cannon
Members of the history department including 2Lt. Robert Seals and Dr. Clifford Rogers getting ready to prep the cannon to be fired.
These efforts were turned into a research paper, “Evolution of Medieval Gunpowder: Thermodynamic and Combustion Analysis,” published this summer in the American Chemical Society’s journal Omega. Riegner received the distinct honor of being named co-author. In addition to herself, other listed writers were West Point personnel such as Riegner’s mother, Dawn E. Riegner, a professor of chemistry; Tessy S. Ritchie, chief chemist; Clifford J. Rogers, professor of history; and Robert J. Seals, a Second Lieutenant in the Second Battalion, Seventh Cavalry Regiment, U.S. Army, and a West Point alumnus.

The paper sparked interest in the wider media with feature articles about the project in the New York Times and the Wired magazine.

“Interdisciplinary projects are pretty cool because you see not just the results of the lab experiments, but you see its impact on the world, and this project was emblematic of that because it mixes chemistry and history,” said Riegner, who is a member of Stevens’s Lawrence T. Babbio ’66 Pinnacle Scholars Program and the Accelerated Master’s Program for pharmaceutical manufacturing.

Edward A. Whittaker, professor of physics at Stevens and Riegner’s academic advisor, lauded her on the gunpowder project.

“It is always important to report the fruits of one’s research labors with an archival publication. But it is a special accomplishment to obtain such results as an undergraduate student because it is pretty unusual to do so before entering a graduate research program. So, Kathleen should be justifiably proud about that,” said Whittaker. “It is a very visible sign that our programs are enabling our students to learn and become outstanding scientists and engineers.”

Two people preparing gunpowder samples
Riegner and Dr. Tessy Ritchie prepping samples for the cannon.
The research team’s main focus was to probe various medieval recipes for gunpowder (also known as black powder), see if there was any “intent” in how people created these formulations, and analyze and understand the recipes at a technical level. The results may “aid historians in their interpretation of medieval texts,” read the paper.

Riegner was eager to join the research team last summer after her mother suggested this unique opportunity to her. Riegner’s main task for the project was to perform experiments on calorimetry, measuring how much heat is absorbed or released in a chemical reaction. She basically tested the potential thermodynamic power of each gunpowder recipe by placing a small amount of gunpowder in a metal canister, connecting it to electrodes, and placing the whole thing in a tub of water and igniting it. She would measure the change in temperature of the water outside the “bomb.”

Gunpowder is one of the most important inventions in human history. Early alchemists in China stumbled upon gunpowder while trying to find medicinal recipes to extend the human life. People in the Middle Ages continued experimenting with gunpowder, coming up with different formulations in an effort to find an edge on the open battlefield or destroy the hefty walls of castles and battlements.

The study focused on several medieval recipes of gunpowder, dating from 1336 to 1420. They mainly consisted of potassium nitrate (KNO3) — also known as saltpeter, charcoal (C), and sulfur (S8). People also added some interesting ingredients such as vinegar, brandy, varnish, camphor, quick lime, and the chemical ammonium chloride (NH4Cl).

The cannon Riegner and her team used in this study.
To further test the recipes, the research team fired the gunpowder in a gun range at West Point. As part of the experiment, they used a reproduction of a firing cannon from the turn of the 15th century. Called a steinbüchse or a stone-throwing cannon, the replica tool of war was copied from an existing one housed in the Bernisches Historisches Museum in Bern, Switzerland. The team poured gunpowder into the barrel and stuffed it with a four-inch diameter marble cannon ball and then ignited it.

The team published conclusions from their experiments: People changed the ratio of saltpeter, charcoal and sulfur over the years as they experimented and tested the recipes. Before 1400, people used more saltpeter while the quantity of charcoal and sulfur declined. After 1400, people started “corning” their recipes, which entailed compressing gunpowder into pucks with water, drying them and then crushing them before screening the granules into different sizes. This process made the combustibles more powerful to use. This innovation was also coupled with a change in gunpowder composition: a decrease in saltpeter and an increase in sulfur and charcoal.

Aside from what she had learned about gunpowder and its chemical evolution, Riegner said she can look back and see how Stevens prepared her for the work she performed that summer.

“A lot of the teamwork stuff that we do at Stevens definitely helped because I learned what it looks like to work in a group and in different environments,” she said. “And one of my key takeaways from this whole endeavor was pretty much learning what it takes to begin a research project and taking it all the way to the finish with a publication.”