"So, how does the improved gunpowder ignite?"
"We use the gunpowder created by His Highness the Crown Prince," Choi Hae-san replied, prompting King Sejong to point out a concern.
"Wouldn't that be too cumbersome? It's like adding another layer of gunpowder between the fuse and the main charge."
All the accompanying ministers nodded in agreement.
Most of them were civil officials, but some had experience in the military, and even those who didn't had at least heard about how firearms were used.
Having witnessed the demonstration, they knew that a fuse was essential to ignite the gunpowder.
Choi Hae-san promptly responded to Sejong's concern.
"We don't use a fuse for the Eul-sik gunpowder. Instead, we use a cap, or rather, a copper fire cap."
"A copper fire cap?" Sejong asked with curiosity, and Hyang quickly wrote the characters on a note and handed it to Sejong.
"This is how it's written."
"Hmm... Do we have a sample?" Sejong inquired, and Choi Hae-san moved a copper plate placed on a table closer to Sejong.
"The smaller one is for hand cannons, and the larger one is for artillery."
"Hmm..."
Sejong examined the copper fire caps on the plate closely.
The one for hand cannons was slightly smaller than a fingernail, while the one for artillery was about the size of a thumb joint.
After inspecting the items, Sejong looked at Choi Hae-san.
"Can we see a demonstration?"
"We're already prepared. This way, please."
Choi Hae-san led Sejong and the ministers to a space about 20 jang (approximately 60 meters) wide and 150 jang (approximately 450 meters) long.
"It's quite barren," Sejong remarked, observing the area.
Indeed, the space was barren, as Sejong noted.
On three sides, except where people stood, there were earthen walls at least 2 jang high.
The area where people stood was also fortified with sandbags piled up to chest height, creating a wall.
Inside the walls, there were numerous pits scattered around.
Once Sejong and the ministers were behind the earthen wall, Choi Hae-san spoke up.
"Let's begin the demonstration. Start!"
At Choi Hae-san's command, the craftsmen who had been waiting moved a small table to the demonstration area.
On the table were copper plates and small wooden barrels.
"The barrel on the left contains Gap-sik gunpowder, and the one on the right contains Eul-sik gunpowder," Choi Hae-san explained as the craftsmen scooped the gunpowder onto the copper plates with ceramic spoons and inserted fuses.
After confirming the fuses were properly inserted, they lit them and stepped back.
Bang! Fizz.
The Gap-sik gunpowder exploded with smoke, but the Eul-sik gunpowder only burned the fuse and stopped.
"Now, we'll use the modified hand cannon with the copper fire cap. Begin."
At the command, the craftsmen brought two hand cannons.
They transferred gunpowder from the barrels into the hand cannons, inserted paper wads, and tamped them down with rods.
After securing the gunpowder, they pulled back the hammer on the back of the hand cannon and inserted the copper fire cap.
Once all preparations were complete, the craftsmen held the hand cannon stock firmly under their right armpit, grasped the string connected to the hammer with their left hand, and faced the opposite wall.
"Fire, fire, fire!"
With a loud shout, the craftsmen pulled the strings simultaneously, and both hand cannons erupted with flames.
"Oh!"
"Wow!"
As the hand cannons spewed fire, the ministers exclaimed in admiration.
Sejong turned to Hyang.
"So, this is why you don't use a fuse? Hmm... It seems there are fewer restrictions compared to using a fuse."
"Yes, Your Majesty."
"You've done well," Sejong praised Hyang with a pleased expression.
But then, Sejong's face turned stern as he asked a question.
"You called the gunpowder you made 'explosive silver.' Surely, you don't use precious silver, do you?"
"No, we use mercury. Of course, mercury is also valuable, but it's easier to obtain than silver, and since it's only used for ignition, the cost is less than expected."
"That's a relief," Sejong's face brightened at Hyang's answer about the reduced cost.
After all, gunpowder was known to consume a tremendous amount of resources.
With his expression much more relaxed, Sejong turned his attention back to the demonstration area.
"I'd like to know about the other gunpowder the Crown Prince created. General?"
"Yes, Your Majesty. Bring the explosive oil."
"Yes."
At Choi Hae-san's command, the craftsmen carefully brought in a small wooden box.
"Tilt the box to show the inside."
The craftsmen tilted the box so that Sejong and the ministers could see inside.
In the center of the box filled with sawdust was a small ceramic bottle.
Choi Hae-san took out the ceramic bottle from the box, removed the stopper, and tilted it slightly toward the empty ground.
Bang!
As a drop of explosive oil fell from the bottle's mouth to the ground, a loud explosion occurred.
"Gasp!"
"Oh my goodness!"
Startled by the unexpected explosion, the ministers were taken aback, while Choi Hae-san introduced it with a mischievous smile.
"This is explosive oil."
"Amazing! Truly amazing! Crown Prince, you are indeed remarkable! This is truly a fitting name for explosive oil! General, how powerful is it?"
"It's incomparable to the gunpowder used by our Joseon army. It would be fitting to say it's as different as heaven and earth. Prepare for the demonstration."
"Yes, General."
The craftsmen prepared a demonstration to compare the power of black powder and explosive oil.
"This is a thick hand cannon made to test the power. The amount of gunpowder used is 1/4 nyang (approximately 9g) on both sides. First, the Eul-sik gunpowder."
The craftsman packed 1/4 nyang of Eul-sik gunpowder into the hand cannon and secured it to a tripod set up on the ground.
Then, they inserted an iron cap shaped like a large mushroom into the mouth of the hand cannon, which was angled toward the front.
After pulling back the hammer and inserting the copper fire cap, the craftsman stepped back and shouted loudly.
"Fire! Fire! Fire!"
Bang!
With a loud explosion, the iron cap flew in an arc and fell to the ground.
The craftsman retrieved the string connected to the iron cap and began counting the distance.
"1 step! 2 steps!..."
Choi Hae-san quickly explained to Sejong.
"We can check the distance it flew by marking it in 1-step increments."
"Is that so?"
"50 steps! (approximately 60 meters)"
"Now, we'll test with explosive oil."
At Choi Hae-san's gesture, the craftsmen began preparations for the second shot.
Their hands were extremely cautious as they loaded the explosive oil into the hand cannon.
"They're being very careful, aren't they?"
Hyang immediately answered Sejong's question.
"It's a very tricky substance."
"Is that so?"
"Fire! Fire! Fire!"
While they were conversing, the craftsman who had finished the preparations pulled the string connected to the hammer.
Boom!
With a much louder and sharper explosion than the Eul-sik gunpowder, the iron cap soared into the sky and began flying far away.
After retrieving the iron cap that had flown a considerable distance, the craftsman shouted the distance loudly.
"110 steps! (approximately 132 meters)"
Sejong's eyes widened in surprise at the craftsman's shout.
"It flew more than twice as far?"
"Yes, Your Majesty. As tricky as it is, its power is exceptional."
Seeing Hyang's expression, Sejong clicked his tongue.
"Tsk! Judging by your expression, it seems it's not something that can be easily used."
"Yes, Your Majesty. In our current situation in Joseon, explosive oil itself is unusable."
"Oh dear."
Sejong couldn't hide his disappointment and smacked his lips at Hyang's answer.
"It's a shame."
"I agree."
The ministers, listening to Sejong and Hyang's conversation, also wore expressions similar to Sejong's.
They knew that the Crown Prince, despite appearing to prioritize performance above all else, surprisingly considered production costs as well.
However, the fact that the Crown Prince hadn't mentioned costs meant that the court could bear the production costs.
Yet, the Crown Prince had just described it as an 'unusable item.'
"How tricky is it that you speak of it this way?"
"It's extremely tricky."
Hyang explained the reasons to Sejong:
- First, it cannot be produced in the warmer seasons of spring or summer.
During the synthesis process, high heat is generated, and there's a high risk of it exploding or catching fire on its own.
For this reason, Hyang could only attempt synthesis when winter began, using a large amount of ice from the ice storage.
- Extreme caution is required during the synthesis process.
Since a highly concentrated acid is used, protective gear must be worn to protect the skin on the hands and face.
Ventilation is also essential.
- Even a small amount of impurity can greatly increase the risk of self-detonation.
For this reason, Hyang had to go through numerous purification processes before and after synthesis.
- Storage is also challenging.
It's extremely sensitive to shock, so if the containers bump into each other or are shaken violently during transport, it will explode immediately.
If lightning strikes nearby, it will explode immediately.
As mentioned earlier, if impurities are not properly removed, it will self-detonate over time.
It must be stored in a cool place due to the risk of self-detonation.
In Hyang's case, he even dug a cave in Mokyeoksan (Namsan) to create a storage location.
"For these reasons, explosive oil itself is absolutely unusable."
"What a cursed item," Sejong muttered a curse without realizing it after hearing Hyang's explanation.
But this time, the ministers agreed as well.
"Indeed, a cursed item."
"The power is truly impressive, but... with such a nasty temperament..."
Leaving behind their regrets about explosive oil, Sejong moved on to the next topic.
"The next gunpowder to introduce is cotton powder."
"Cotton powder? Is it named so because it uses cotton? No, do you use cotton in gunpowder?"
Recalling Choi Hae-san's explanation from when he first saw it, Sejong looked incredulous.
The ministers felt the same way.
"Making gunpowder with cotton?"
"Of course, cotton burns, but..."
While Sejong and the ministers muttered in doubt, Choi Hae-san picked up a piece of cotton cloth with tongs from the table.
"Light it."
"Yes, General."
Bang!
"Oh my goodness!"
"Good heavens!"
As soon as the craftsman set fire to the cloth, it instantly burned with a loud explosion, turning to ash.
Watching the ministers flinch at the explosion, Choi Hae-san chuckled and spoke.
"It's made using well-woven cotton and various types of acid. As you can see, it has powerful firepower. And... there's something most important. Starting from explosive oil to cotton powder, and the Deokgap-sik gunpowder, they are smokeless powders."
"Smokeless... does that mean it doesn't produce smoke?"
"To be precise, it produces very little."
In the subsequent demonstration, cotton powder showed power that was weaker than explosive oil but still stronger than black powder.
"The last one to show is the Deokgap-sik gunpowder."
"Deokgap-sik? Why is it named so?"
In response to Sejong's question, Choi Hae-san looked at Hyang.
Following Choi Hae-san's gaze, Sejong and the ministers all focused on Hyang.
Hyang scratched the back of his head and answered.
"Uh... I thought it was a virtue for soldiers using gunpowder to use it comfortably, and since it was possible because of Your Majesty's virtue, I named it so."
"Hmm?"
"A bit embarrassing, but quite a good name."
Sejong and the ministers nodded at Hyang's explanation.
However, Hyang had to force a bitter smile. 'I can't possibly say it was named after the German method I learned from internet fandom, called Deokguk!'
Choi Hae-san continued his explanation.
"This Deokgap-sik gunpowder is a mixture of cotton powder, explosive oil, and camphor oil (glycerin) in a certain ratio."
Sejong, surprised by the mention of explosive oil, raised a concern.
"You mixed explosive oil? Didn't you say earlier that explosive oil is too tricky to use?"
"Cotton powder and camphor oil neutralize its properties."
"Is that so? But why is this gunpowder black when cotton powder is white?"
"It's coated, or rather, wrapped in graphite."
In the subsequent power demonstration, Deokgap-sik gunpowder displayed power comparable to explosive oil.
Seeing its power, Sejong clapped his hands in delight.
"Truly excellent! Excellent!"
Seeing Sejong so pleased, Hyang wore a proud expression. 'As expected, Deokguk!'
However, Hyang's memory was mistaken.
The combination he remembered was not German but British.
To be precise, it was the formula for Cordite MD.
Sejong, who was very pleased with the newly developed gunpowder, turned to the ministers.
"Since such excellent gunpowder has been developed, how about mass-producing it?"
At Sejong's suggestion, Hwang Hee asked Hyang about the production cost.
"What is the production cost?"
"It costs about 30% more than producing the same weight of Gap-sik gunpowder. However, using only half the amount of Gap-sik gunpowder yields more power."
At Hyang's answer, Hwang Hee nodded and advised Sejong.
"Although it costs more, it can be offset by using less, so it seems wise to mass-produce it."
"The Right State Councilor's words are correct."
As the ministers expressed their agreement, Sejong looked at Hyang and Choi Hae-san.
"Prepare for the mass production of Deokgap-sik gunpowder."
At Sejong's command, Hyang replied with a troubled expression.
"I apologize for saying this, but in our current situation in Joseon, mass production of Deokgap-sik gunpowder is impossible."