The Crucible Furnace
“What did you say? A boy who claims to know about hundred-refined pure steel spouts nonsense like that?”
Hundred-refined pure steel meant, quite literally, iron that had been refined a hundred times—and in this era, that was nothing other than steel itself.
Steel could not be obtained through ordinary ironmaking. The impurities mixed into the iron ore had to be driven down below a certain threshold. That was common knowledge of the age.
Yet Hui-yeom stood up and challenged that knowledge head-on.
“Father, if the furnace itself is good enough, hundred-refined pure steel does not need to be forged at all. No—the very idea that you have to hammer wrought iron into hundred-refined pure steel already proves the furnace’s performance is pathetic.”
Dang Un-sang’s face became the expression of a man who could not decide whether he ought to get angry or not. He drained his tea in one gulp, took a long breath to recover his composure, and spoke.
“…Haa. Fine. You’re clever. I know perfectly well you’re not a child who spouts empty nonsense. So say it again. What about hundred-refined pure steel?”
“Father, if I may be so bold—why is it called hundred-refined pure steel in the first place? Because an iron ingot taken from the furnace is refined a hundred times, literally, to remove impurities and raise its strength, is it not?”
“That’s right.”
“To remove those impurities you heat the ingot, hammer it, quench it in water, heat it again, hammer it again, quench it again… After you’ve repeated that roughly a hundred times, why does the quality of the iron improve?”
“Because you’re tempering it, aren’t you? Just as a man’s bones and muscles grow bigger and stronger the more he uses them, an iron ingot grows stronger the more you strike it.”
“If striking it made it stronger, then a finished sword ought to grow stronger every time it clashes with another blade—yet instead the edge chips, it bends, and it breaks, doesn’t it?”
“Well, even exercise, if you overdo it, wrecks the body, and in severe cases you get injured. Isn’t that the same reason?”
Ah, so people of this era understand it that way?
Compared to modern people who learn basic physics and chemistry in middle and high school, the warriors of the jianghu, even when looking at the same phenomenon, naturally explained it through the lens of yin and yang, the five elements, and the eight trigrams.
Well, Father isn’t a blacksmith either, so it’s only natural he wouldn’t have a deep understanding.
Hui-yeom gave Dang Un-sang a simple explanation of the principle by which forging produced steel. In the forging process of melting iron at high heat, striking it, and quenching it, the impurities inside the ingot were driven out. In particular, iron made by the crucible method inevitably developed air bubbles, and the hammering process was necessary to solve that problem. Only after hearing the full explanation did Dang Un-sang finally grasp the principle.
“I see. When you make iron by the crucible method, you have to stir the molten ore with an iron rod so that the whole mass melts properly and the heat circulates inside. But at that moment air bubbles get mixed in, leaving many small hollow spaces inside the ingot.”
“Yes. And if those hollow spaces remain, when the metal takes a shock it starts cracking from the empty parts first. That’s why you have to hammer it beforehand—to burst and drive out those bubbles.”
“Yet with this crucible furnace you’ve proposed, you claim you can obtain hundred-refined pure steel without those bubbles forming at all?”
“The fundamental reason you have to stir the molten ore with a rod in the crucible method is that the furnace temperature is too low; heat alone cannot burn out and filter the impurities. But a crucible furnace can generate far higher heat than anything existing, so the stirring process becomes unnecessary.”
Strictly speaking, it was less a matter of burning the impurities away than of melting them so they could be separated by density difference, but the explanation would grow complicated, so Hui-yeom glossed over it. Dang Un-sang did not press the point either.
“Hmm. I see. And another thing—you’re not using charcoal as fuel, but this ‘coal’? You mean burning stones?”
“Coal and coking coal are precisely the secret to high heat. In truth the crucible furnace is nothing more than a means of holding that high heat efficiently. Once the crucible furnace succeeds, I will next design a different furnace capable of mass production.”
What Hui-yeom actually had in mind was the puddling reverberatory furnace developed by Henry Cort. That level of technology could be built with current methods and would still produce steel in large quantities. The crucible furnace could make excellent steel, but the amount it could produce at one time was its greatest weakness. The reason he had not begun with the reverberatory furnace was simple economies of scale.
A puddling furnace loses money the smaller you make it and profits the larger you make it, so you have to build it big. If I pushed that with no track record, the Council of Elders would throw a fit.
It would not be easy to allocate funds for a large furnace without any justification. First he would demonstrate high-quality steel production with the crucible furnace, then proceed step by step.
“Hmm…”
Dang Un-sang stroked his chin for a moment, then nodded.
“Very well. I’ll approve it.”
“Thank you for trusting me, Father.”
“It’s all for the good of the family—what’s there to thank me for? More importantly, enough of this stiff talk. My son, is anything weighing on you these days?”
“Pardon? Uh, um… other than business matters?”
“Yes. Let’s just chat, father and son.”
“Chat… a chat, huh… Then shall I tell a joke?”
“All right, what is it?”
“Do you know what weapon every person carries with them?”
“Hmm. Since you said weapon, it can’t be a trained body… Let’s see—are you talking about a hairpin?”
“The answer is hair.”
“?”
“Hair-‘knife.’”
“?”
“Pff—pfft, hair-knife… heheheheh…!”
“…Son?”
Dang Un-sang began to worry in earnest that his son, who had been overworking lately, might have gone a little strange.
A few days later, Hui-yeom headed for the kiln grounds of Cheol-u-jeon, the Hall of Iron Rain.
As the place that produced every kind of ironware used by the Dang Family, Cheol-u-jeon naturally possessed its own furnace facilities. Hui-yeom had been allotted the site of Furnace Number One, which was already old and scheduled to be torn down and rebuilt according to his proposal.
Before he could produce high-quality steel, he first had to build the furnace itself.
The overall site manager Dang Un-sang had assigned him—Master Builder Gwak, the chief of the construction crew—approached with a blunt expression and bowed stiffly.
“Master Builder Gwak presents himself before the Young Master.”
“I’m glad to meet you. I am Dang Hui-yeom. I would be delighted if you would lend a hand for the bright future of the Dang Family.”
When Hui-yeom greeted him with a more courteous and open manner than he used even with the elders, the prideful master builder silently nodded. In truth, no matter how senior a master builder he was, he was ultimately only one of many foremen under Cheol-u-jeon. There was no need for the Young Master to speak so politely to him, yet the man, armored in a craftsman’s peculiar pride, felt both satisfaction and a sense of novelty at the Young Master’s attitude.
Of course Hui-yeom was simply acting on personal experience and management philosophy.
You can ride a department head or a director hard and the company won’t stop, but if you hurt the feelings of a factory manager or a site chief, the factory or the site can grind to a halt.
The master builder stared for a moment at Hui-yeom’s smiling face, then asked,
“I heard you’re building a new furnace. They say the structure is different?”
“That’s exactly what I wanted to discuss with you first, Master Builder. Here is a rough design I drew…”
“Hmm, let’s see.”
Expecting a child’s scribbles and already fretting over how to interpret them, the master builder’s eyes flew wide the instant he looked at the blueprint.
“Huh. The Young Master drew this himself?”
“Yes. Is it very strange?”
“Strange? It’s better than the freeloaders under me who just eat rice and do nothing.”
I used to design production lines myself with CAD back in the day, you know.
Hui-yeom secretly squared his shoulders. The design outsourcing fees had been so painful that he had attended night school, learned from the designers he hired, and spent a full twenty years drawing blueprints. He could produce designs that would not look out of place even beside those of decent team-leader-level designers.
The lack of a computer was the hard part; everything else was fine…
Drawing with CAD had already been hard labor, but in this world blueprints were drawn with ink on hanji paper. Hui-yeom himself had worried about how to draw precise lines without a computer. Once he learned that the craftsmen stretched ink-soaked threads taut and snapped them onto the paper for straight lines, and used dedicated wooden frames for curves and circles, he simply adopted the methods of the age.
The reason he knew the structures of crucible furnaces and puddling reverberatory furnaces was purely the extension of a hobby. After the company grew large enough that he no longer needed to design himself and could hire better designers, he still hated to let the skill he had worked so hard to acquire rust away. So whenever he had free time he studied historical buildings, machines, and fortresses, drew blueprints of them, and recreated them in 3D graphics. The result was the crucible-furnace drawing now in front of them.
“Hmm. The structure is quite different from existing furnaces. Why build it this way?”
“Ah, that is…”
The master builder asked question after question with genuine interest, and Hui-yeom answered each one, helping him understand. The structure of a crucible furnace was not especially complicated to begin with, so the answers came without hesitation. By the time the exchange ended, a strange light glittered in the master builder’s eyes.
“That the Young Master devised this… I’m astonished. I want to build this crucible furnace at once and see whether it truly can produce hundred-refined pure steel that needs no forging.”
“I’ll be counting on you, Master Builder.”
“Is there any doubt? I, Gwak Do, stake the name of master builder on making the finest furnace!”
When Hui-yeom left, the carpenters who had been watching from a distance sidled closer.
“Hyung-nim, let’s have a look at the drawing.”
When Deputy Master Builder Im requested it, the master builder handed over the blueprint, and a dozen pairs of eyes scanned it at once.
“Never seen a furnace structured like this.”
“Hmm…”
“Will this even work?”
“Who knows? We’re the ones who put up the buildings, not the ones who work the metal, right?”
“At least it doesn’t look like a structure that’ll collapse. Doesn’t seem like half-learned skill…”
The deputy’s gaze slid to the master builder.
“Is this really a design the Young Master made, hyung-nim?”
“Seemed that way. If he hadn’t conceived and designed it himself, he couldn’t have answered my sudden questions so calmly and completely.”
“Hah. Amazing. I heard a seven-year-old made that incredible medicine and ointment and figured the Family Head was just forcing the Young Master’s prestige up… but…”
“He’s a genius, I suppose. Those kinds of people show up every now and then, don’t they? Anyway, lucky for our Dang Family, isn’t it?”
“True enough.”
“But won’t the Council of Elders raise hell? If the sparks fly our way…”
“Sparks? What sparks?”
“Well… word is the Council of Elders doesn’t look kindly on the Young Master. Just recently…”
At one carpenter’s words the master builder’s face turned ugly.
“Hey, Jin Chung-sik. Whether the Council of Elders is at odds with the Family Head’s Hall or throwing whatever tantrum they want, what does that have to do with anything?”
“Come on, you know how it is. The blacksmiths are pure Dang blood, so of course they get dragged around by the Family Head’s Hall, but most of us woodworkers are side-branch. Do we really need to make enemies of the Council just to help the Young Master… that kind of talk.”
“Jin Chung-sik, you little bastard—I thought you were a craftsman, but you’re a politician?”
“No, Master Builder, what I mean is…”
“They already planned to tear down the old furnace and rebuild it, so what the hell are those bastards even ranting about? Those guys and I are the same—neither of us pure Dang blood, both rocks that rolled in from outside. So what? When an elder shows up and clears his throat, am I supposed to go ‘Oh my, Your Lordship’ and wait on him? Or are we supposed to pick sides in a grown-up power struggle, grab hammers, and run over to smack the Young Master in the back of the head?”
“Of course not.”
“Where’s ‘your side’ and ‘my side’ inside a family, you rotten bastard? This is work for the good of the household. Anyone who complains about that is a piece of shit from the Council of Elders no matter how you look at it. And bastards like that need to get the absolute shit beaten out of them. You understand what I’m saying?”
“…Yes.”
“I’m the master builder. On this site I’m the king. If an elder or anyone else comes here and starts shit, tell me. I’ll check whether he still clears his throat after his head’s been cracked open by a hammer.”
“….”
“All right, let’s get to work. We’re about to get very busy.”
Hearing that solid voice—craftsman’s pride mixed with goodwill toward Hui-yeom and pure loathing for the Council of Elders that was rotting the family while clinging to authority through power struggles with the Family Head’s Hall—the craftsmen each answered “Yes” and picked up their tools.
One craftsman who was the son-in-law of an elder and leaned toward the Council of Elders found the taste bitter, but he had no choice except to follow the majority.
And a little farther off, in the shade, Ye-eun quietly observed the scene. Following Hui-yeom’s instructions, she had been watching the craftsmen’s stir. After carefully noting the one who had spoken up to the master builder and gotten nothing for his trouble, she silently moved on.