Along with other chemists and historians at the academy, they began their research in early 2020, during the first wave of the COVID-19 pandemic. Riegner also brought her daughter, who is currently a chemical engineering student in Hoboken, N.J., into the mix.
While the rest of the team socially distanced, the mother and daughter worked side-by-side in a West Point laboratory, carefully measuring the ingredients and cooking up 23 different gunpowder recipes.
Each of the recipes from the medieval gunners between 1338 and 1460 had its own ratio of the base ingredients: sulphur, carbon and potassium nitrate (also known as saltpeter). The gunners likely used charcoal for the first two elements and added saltpeter to it, which can quickly ignite an explosive combustion, Riegner said.
Some recipes also used unusual ingredients, including brandy, varnish and vinegar.
"We wanted to know, did they add these things to increase the amount of energy? Or was it some other reason?" Riegner explained.
Once the team of chemists and historians prepared their concoctions, a lieutenant from the military college helped them take all that gunpowder onto the firing range. Using a diagram, he enlisted a foundry to recreate a medieval cannon.
Then, on a sunny day in June 2020, the experts lined up in their flak jackets and helmets — along with medics nearby — at the academy's world-class firing range.
"It's very exciting ... and you can feel it in your gut. It's one of those kind of adventures," Riegner said.
"The cannon fired just beautifully."
What they saw in the explosions that day revealed the true intentions behind the medieval gunners' work.
They found that the most powerful ratio for gunpowder had three times less sulphur than saltpeter. But the more powerful it was, the more dangerous it became for them to handle and transport for use in their weapons.
"They had to tweak their ratios," Riegner said. "They honed in on a particular ratio and it was able to still give them pretty good power, but they had to use the most expensive ingredient, which was not the brandy ... [but] the saltpeter."