Fire medicine.
I always thought it rather funny how a compound responsible for millions of deaths throughout history was discovered as part of a quest to produce an elixir of eternal life. Taoist alchemists sought a substance to preserve the status quo, but instead discovered one that sparked numerous revolutions.
Gunpowder.
It brought down feudalism and ended the age of knights, paved the way for centralised states that extended across the world, and allowed for almost anyone to oppose their oppressors with minimal effort. Not to mention it propelled chemistry, metallurgy, and engineering into the modern age.
And yet, all it takes to make this wonder-weapon is just three ingredients.
Charcoal. Sulphur. Potassium nitrate.
***
Charcoal was the easiest to obtain.
Otto’s forge used sacks of charcoal weekly, and the nearby forests provided plenty of wood. Still, the kind mattered. Different woods made different quality of powders, and I wasn’t sure which were the best. Because of this, I asked the poachers to bring me as many wood samples as they could find, planning to experiment until I found the right ones.
Next was sulphur.
Here, I was in luck, since the mountains around Rand held rich deposits of lead and zinc. And among these minerals, one more is often commonly found: fool’s gold. Iron sulphide. To medieval miners, it was useless—even with modern technology, it is a poor source of iron—but it was an adequate source of sulphur. And unlike different kinds of wood, sulphur was just sulphur.
The problem was getting it out of the rock.
When I was making phosphorus, I needed just sulphuric acid, which was much easier to obtain. But now I needed full thermal decomposition. This meant pyrite had to be roasted for several hours inside a crudely-sealed clay retort with restricted airflow. This way, the iron sulphide broke apart rather than burning away, driving off sulphur vapours. Channelled through a clay pipe kept cool with wet rags, the vapour condensed along the inner walls as crude, bright yellow crystals. Some dioxide escaped regardless, making the manor reek of burnt matches for days, but the yellow deposit collecting in the pipe was unmistakable. It was elemental sulphur.
Now, only potassium nitrate was left.
It was the hardest to obtain. Despite the atmosphere being mostly nitrogen, fixing it into a useful form wasn’t possible even on Earth until fairly recently. It was only in the early 20th century that Haber and Bosch freed humanity from dependence on natural nitrate deposits, turning nitrogen into a limitless resource. This abundance allowed mankind to make bread from air and support billions more people than before—the discovery rightly earning its place as one of the greatest achievements of industrial civilisation. Not to mention it allowed for the mass production of cheap explosives, pharmaceuticals, and even rocket fuel.
I got goosebumps every time I thought about it.
Unfortunately, such elegant methods were likely decades away from my current situation, meaning I would have to make do with more… crude methods.
***
“You want us to do what?” Ralf gawked at me as I explained the army’s new task.
It was about the reaction I expected.
“Scrape the floors. The stables, the latrines, anywhere animals or people have been doing their business for years. Everything goes into buckets.”
“You’re not serious.” He looked at Kurt, who had gone carefully neutral in the way he often did when he had already decided not to be the first to object. “Tell me he’s not serious.”
“There are crystals that form in the soil beneath old latrines and stables, and they contain a compound I need,” I explained. “It cannot be obtained any other way with what we currently have available.”
“Crystals?” Ralf continued. “What kind of crystals grow in shit?”
“Potassium nitrate. It’s something that forms when bacteria break down organic matter. The older the floor, the richer the deposit.”
“Potted night-root? Back area?” Ralf stuck out his tongue as he muttered the unfamiliar words.
He once again looked to Kurt for ideas, but Kurt simply shrugged.
I sighed as I caught myself over-explaining again. I had to remember I wasn’t talking to my classmates or people with modern common sense. “I can’t explain to you the entire process behind it, but that is what we need right now. If it makes it any easier, consider it an order, Lieutenant Ralf.”
Ralf’s expression cycled through several emotions before settling on something between outrage and resignation. “You’re telling me we trained all winter.” He pointed at the floor. “And now the grand plan is to dig up the bailiff’s old shit.”
“The grand plan,” I said impatiently, “is to make something that can out-blast a mage and shatter a knight’s charge. This is just one step.”
“One very fragrant step,” Kurt offered with a sheepish smile.
“I will make you some respirators that should dull the worst of it. The work shouldn’t take more than two days if everyone pitches in.”
Another silence.
“Two silver,” Ralf finally said, holding up two fingers.
“You will get three if you are done before sunset tomorrow.”
“Done. And you don’t tell anyone what we dug through. Especially not the recruits!”
I hadn’t planned to in the first place.
The reason I specifically sent just the four poachers was that I wanted to keep the details of the process a secret as long as I could. Given whispers I had been hearing about some peasant somehow still being dissatisfied with their newfound freedom, I didn’t want to take any chances.
“Huh, I still don’t get it,” Lili said, turning to me once Ralf and Kurt left. “How can charcoal, smelly rocks, and cooked shit defeat magic?”
“Lili!” Erika admonished her with a light tap on the back of the head. “Watch your mouth in front of the prince.” She then turned to me with a more composed expression. “However, I am curious as well, my lord. It seems a very simple ingredient list for something you claim to be so powerful.”
I paused for a moment, thinking about how best to describe it to them.
“Well, by themselves, those ingredients are rather unimpressive; that is true. However, when they are combined in a specific way, they make something new.” I tore away a page of one of Ugo’s books and brought out my quill. “Charcoal, you already know about. Especially you, Lili. It is a fuel. Here it is much the same. However, instead of it simply burning for a long time, we want it to burn up all at once, releasing all of its heat in an instant. Potassium nitrate—cooked shit, as you called it—is what enables the charcoal to burn very, very fast. Sulphur has a similar role, making it easier to ignite the charcoal.”
“But how would that stop magic or a knight’s charge?” Erika asked as she studied the rough sketch. “Do you intend to quickly burn them before they can cast a spell?”
“Not quite,” I returned to the sketch. “The plan is to stuff the mixture inside a sealed clay jar and then ignite it. The sudden release of heat will cause it to build pressure inside the jar, which will at some point cause the jar to shatter, releasing a blast of air and fragments of clay all around it.”
It would, of course, be better if the casings were made out of iron, but if we had enough of it, I would probably avoid this altogether and just go straight to making rifles.
“Oh, so it’s like when a charcoal pops in dad’s forge!” Lili cheerfully concluded.
“Yes! Yes.” It was not a perfect analogy, but it was good enough. “A charcoal pops because of the moisture inside that expands when heated. Here, it’s air that expands when heated by the mixture.”
“When you explain it like this, it seems very straightforward,” Erika mused. “But then why has no one figured it out already?”
“That is a million-dollar—I mean, a million-gold question. Many inventions seem very obvious in hindsight. I suppose someone simply didn’t mix these three things in a specific ratio and tried to set it on fire. The mixture itself was discovered by accident… by some alchemist my father employed. It goes to show the value of trying things out until something interesting happens, recording what you find, and then trying again to get better results. It’s the basis of the scientific method.”
“Scientific method?” Erika asked with a curious gaze.
“Indeed. It’s humanity’s ultimate tool and weapon,” I smiled. “Don’t worry, you will get to see it in practice soon enough.”
Erika nodded in consideration. Lili, on the other hand, was seemingly a bit too eager to apply my words as she was already looking at the yellow sulphur crystals on the desk with new interest, turning one over between her fingers.
"Don’t smell that—“
She already had. Her face confirmed it was not worth it.
***
Two days later, all three ingredients were laid out on the desk in front of us.
It was time to pull up our sleeves and begin the final step of the process.
The theory I knew by heart. Seventy-five parts saltpetre, fifteen charcoal, ten sulphur.
I measured everything as carefully as the available equipment allowed, combined the powders in a clay bowl, and ground the mixture together with a pestle.
Sure enough, a black powder soon formed in the bowl.
The first test used a pinch of it on a flat stone.
I touched it with an ember and took a step back, bracing for the explosion…
But nothing happened.
The gunpowder spat a few coughs of thin smoke and quickly fizzed out.
I stared at it.
Erika stared at it.
“Is that… it?” she asked, poking the residue with a stick.
It was not supposed to be.
I ground the next batch longer, reasoning that the particle size was too coarse. Same result. A sullen sputter and a small smear of black residue on the stone.
The third batch I ground for nearly an hour until my arms ached, then tested a larger portion. This time it burned with a satisfying hiss and a brief orange flame, but it was still far too slow. I needed near-instantaneous combustion if I wanted to blow something up.
I sat back and thought.
It had to be the charcoal.
Not wanting to waste the limited supply of nitrate, I simply picked out a few samples that seemed most promising and figured it wouldn’t make too much of a difference. But clearly I was wrong.
I spent the rest of the day retesting each wood sample systematically, burning the smallest amounts I could get away with and recording the results in the margins of what used to be Ugo’s ledger. In the end, willow—Lili told me the species, as I had zero knowledge of botany, produced the finest, lightest ash. Seeing this, I re-charred a fresh batch overnight in a sealed pit, and ground it to a dust so fine it left a black cloud hanging in the still air of the hall. Then I tried the following morning again.
This time, the reaction was noticeably better. The burn was faster, sharper, almost eager.
But it was still not right.
To my surprise, Erika noticed it first.
“The mixture separates,” she said, pointing at the bowl. “Look. The white crystals settle to the bottom. By the time you test it, it is not the same mixture you ground.”
She was right. I stared at the bowl and felt genuinely stupid.
It made sense when I thought more about it. There wasn’t really anything that made the three components necessarily stick to each other. I was so convinced the process was trivial by itself that I must have overlooked it.
I arrived at a solution—quite literally—only after a few more failed experiments. The answer was to add a small amount of water and work the mixture into a damp paste. I pressed this paste through a piece of coarse linen to form crude granules, which I set near the hearth to dry.
This time, the result was considerably better.
The flash was immediate and violent enough to make both of us flinch back from the table. The stone cracked, and a black scorch mark spread across the stone beneath it.
Neither of us spoke for a moment.
“That,” Erika said quietly, a smile on her face, “is much more impressive.”
It was. But I needed to know just how impressive it was before I handed it to someone to throw. I packed a generous amount onto a plate and carried it outside.
I set the plate against the base of the old fence post at the far end of the yard and lit the mixture.
I realised too late that the ignition stick was much too short.
The blast knocked me sideways into the snow.
My ears rang. The plate was gone. The fence post was gone. Something warm ran down the side of my face. And the blast had left a shallow crater in the frozen earth.
I lay there for a moment, taking stock of whether I was injured.
Erika quickly ran over to the scene of the explosion, her medical bag in hand.
In the end, it turned out there was no blood, and I had just fallen face-first into a patch of mud hidden under the snow. Thankfully, it was only my dignity that got hurt.
***
We made six more test vessels over the course of the night, each one more refined: better granule consistency, standardised fuse length, optimised casings...
In the end, the final design was much simpler than the phosphorus grenades I made earlier. There was no need for a water chamber, just powder and a fuse. I also carved fragmentation grooves around the outside, though I wasn’t entirely sure how much a clay shell would actually fragment. If nothing else, it at least looked more like the grenades I was familiar with.
And with that, it was ready.
For the final test, I sneaked out with Lili and Erika to an open field some distance from the manor. Despite my attempt to keep it a secret in case I got blown up again, a crowd quickly formed. Dietrich and Wulf insisted on coming. So did Kurt. And Ralf came on the basis that nobody had told him not to, which was technically true.
“How loud will it be?” Lili asked as she watched me set the grenade against a rock.
“Loud.”
“Louder than a thunderstorm?” Ralf eyed the rock sceptically.
“Hopefully,” I concluded with a smile as I brought a torch down on one end of a rope soaked in nitrate solution.
The fuse caught on the second attempt.
The cord made a bright, hissing streak as it burned down.
Then it reached the clay sphere.
That morning, Rand was awakened not by sunrise but by a blast of this world’s first industrial weapon.