"That was very instructive. Thank you."
Jin expressed his gratitude to Duston.
"Hanna, were you watching? That’s how your grandfather used to make all sorts of things."
"Yeah, I saw. It’s so different from how you do it, Onii-chan..."
Jin patted Hanna's head. "True. On the flip side, I can't actually make things that way."
He then turned to Elsa and asked, "Well? What did you think?"
Elsa replied, her face slightly flushed with excitement. "N. I understand now how the knives and tools we use every day are made. It was helpful."
"Exactly. And that last part—the quenching and tempering—is vital for iron and steel," Jin explained.
Naturally, Elsa had a follow-up question. "How so?"
"Listen, steel is a type of iron. If you heat it until it turns a citran color and then cool it suddenly, it becomes hard. That’s quenching."
"N."
"But if you leave it like that, it’ll be hard but brittle. It would snap immediately. That’s why you do tempering to give it toughness. You keep it at a temperature where a drop of water would bead up and dance, then let it cool slowly."
"N, I understand."
"Knowing this can make a world of difference in the quality of your magi craft."
Just as Jin finished his explanation, Duston approached them with a stern expression.
"H-Hey now, young man! Where did you hear that secret? Normally, that knowledge isn't taught until a master recognizes his apprentice as a full-fledged craftsman! Even I wasn't taught that until I was over thirty!"
He seemed shocked that Jin, who looked younger than twenty, knew such things—though Jin was actually twenty-one.
"Who? My teacher taught me."
"Your teacher is either incredibly generous or just plain amazing..." Duston looked exasperated.
"Hey, Onii-chan, show us how you make a kitchen knife too."
"N. I want to see Jin-nii make one as well."
Hanna and Elsa's prodding brought a wry smile to Jin's face. He turned to Duston.
"Would you mind if I used your workshop?"
"Sure, let’s see what this 'Magi Craftman' work is all about!" Duston readily agreed.
Jin immediately went over to the iron ingots.
"『Analyze』... Hmm..."
After checking the quality of the iron, Jin called Elsa over to teach her.
"Elsa, come here a moment. Look, 『Analyze』 is for investigating the composition of this iron, but you can't understand what you don't already know. That’s why knowledge is a prerequisite."
Saying that, Jin cast the Analyze spell, confirmed the contents for himself again, and then told Elsa to try it.
"N. 『Analyze』."
She succeeded on her first try, but she frowned. "...I kind of understand the iron. But the rest is so cluttered that I can't make sense of it at all."
"Haha, that's only natural. Watch. 『Extraction』: Copper. 『Extraction』: Silicon. 『Extraction』: Sulfur. 『Extraction』: Phosphorus."
Jin cast Extraction four times on the base ingot. This separated small amounts of copper, silicon, sulfur, and phosphorus from the mass. Each was small enough to fit in the palm of a hand, but as impurities, they represented a non-negligible amount.
"See? These are the impurities. Each one is now a pure substance, so try casting Analyze on them individually."
"N. 『Analyze』... Oh."
"How is it?" Jin asked Elsa, whose face showed a hint of surprise.
With her cheeks slightly flushed, she replied, "I understand the copper and sulfur a little better now."
Perhaps because they were relatively familiar substances, Elsa was now able to identify them.
"Good. It would be rude to take up too much of his time, so that's the end of today's lesson. Just watch the rest."
"N."
Jin finished his lecture to Elsa and resumed the knife-making process. He didn't notice that Duston's jaw was practically hitting the floor behind him. Reiko stood beside the blacksmith, her chest puffed out with pride.
"『Separation』. 『Forming』."
Using Craft Magic, Jin separated the necessary amount of iron. With the following spell, the iron changed shape in his hands, becoming a kitchen knife.
"Alright, that's the shape. Next is the heat treatment—or so I'd like to say, but the carbon content is a bit low."
Based on Jin's check, the carbon content was about 0.5 percent. Carbon content is the factor that most affects the hardness achieved through quenching; for a kitchen knife, 0.8 to 1.2 percent is ideal.
"『Carburizing』."
He decided to extract carbon from the carbon dioxide in the air and mix it into the iron. Since this spell only allowed carbon to be introduced to the surface, he used the Craft Magic 『Homogenize』 to make the composition uniform throughout.
After repeating this a few times, the carbon content reached 1 percent. It was just right.
"Alright, Elsa, watch closely. 『Heat Treat』."
Because he did it slowly, Elsa—who was observing while tracing the flow of mana—could feel the knife in Jin's hand flash-heated, then rapidly cooled, then lightly heated once more, before returning to room temperature.
"Isn't it hot?"
Having felt the temperature rise to the point where the iron turned a citran orange—even if only for a moment—Elsa asked worriedly.
"Oh, it's fine. What you felt was strictly the change in the state of the iron; the metal didn't actually reach that physical temperature. That’s the beauty of Craft Magic."
Saying so, Jin handed the knife to Elsa. She felt for herself that it indeed wasn't hot.
Behind them, Hanna's eyes were sparkling. Beside her, Duston's eyes were wide enough to match his hanging jaw.
"Let's put an edge on it last. 『Shaping』. And let's clean up the surface, 『Finish』."
The dull-colored knife took on a shining silver-gray luster.
"There, finished. Duston-san, do you have a handle I could fit to this?...Hello?"
When Jin turned around, Duston had an indescribable look on his face.
"Hello? Duston-san?"
As Jin called out to him, Duston finally snapped out of it.
"A-Ah, right. It's my first time seeing a Magi Craftman's work, so it gave me quite a shock. But—but wait! What did you do to that ingot!?"
He was referring to how Jin had separated the impurities.
"Oh, that. There were quite a lot of impurities, so I just separated them out."
"...You can even do that...?"
Duston seemed a bit drained of strength.
"Right, a handle. This is the standard handle I use."
It was a knife handle made of hard wood. Since the knife Jin made was almost the same size as Duston's, he simply fitted it, and the job was done.
Gloria, who had been watching Jin's work in a similar fashion, had also been dazed until then, but she recovered herself.
"J-Jin-dono! You are amazing! As I thought, Lishia wasn't exaggerating! Won't you make a sword for me quickly!?"
The "disappointing beauty" was back in top form.
Jin gave a single nod. "I understand. So, what kind of sword would you like?"
"For us female ritters, the official equipment is a short sword. A blade length of fifty centimeters and a hilt of about twenty centimeters is desirable."
The "short sword" mentioned here was called such in contrast to the long swords used on horseback. It did not mean a dagger.
"Understood."
Saying so, Jin secured the necessary amount from the previous ingot using Separation. Since he knew the specifications of Lishia’s sword, he had a general idea of the weight needed.
Then, after going through Forming and Carburizing, he applied Heat Treat, Shaping, and then Finish.
Finally, he applied Hardening, and the sword itself was complete.
Elsa, who had been watching the whole time, asked a question.
"Jin-nii, why were there fewer Carburizing steps compared to before? And you didn't use Homogenize."
"Oh, you were watching closely. See, for a sword, the worst thing that can happen is for it to snap. The ideal is something that doesn't break, doesn't bend, and stays sharp. To achieve this, I use a composite material."
"Composite material?"
"Yeah. In other words, I use relatively soft iron for the core and hard steel for the blade part. Then I harden the surface."
Once he said that much, Elsa looked up with a look of understanding.
"The core is soft, so it’s hard to break. If you carburize only the surface to make it rigid, it’s hard to bend. And if you apply hardening, it cuts well."
"Correct."
When Jin praised her, Elsa's cheeks flushed slightly with pride.
"Y-Y-You! I've never heard of that manufacturing method before! Is it really okay to speak so freely about such a secret technique?"
Duston, who had been listening from behind, spoke up excitedly.
"Eh, it's fine. I used your workshop, Duston-san, and you're letting me use your iron. Oh, do you have materials to make a scabbard and hilt for the sword?"
Jin's casual response took the wind out of Duston's sails, and his excitement calmed.
"Hah. The young lady certainly brought along someone incredible."
As he said that, he pointed to the material shelf in the back.
"Feel free to use anything over there."
Jin looked through the shelf.
He chose thick leather for the scabbard, bronze for the crossguard, and hard wood for the hilt. These too were shaped and processed in a short time using Craft Magic, and finally, the short sword was complete.
"Gloria-san, thank you for waiting. Please check it."
"Mm, thank you."
Receiving the short sword, Gloria immediately drew it from its scabbard and gave it a light swing.
"How is it? I can adjust the weight balance a little, so please don't hesitate to say so."
"Let's see. I feel it is slightly tip-heavy."
Prompted by Jin, Gloria gave her impressions.
"Understood. You can keep holding it just like that....『Forming』."
Jin subtly adjusted the tapering shape of the blade.
"How is it now?"
Gloria swung the short sword once more.
"Mm, this is perfect! My thanks, Jin-dono!"
She expressed her gratitude with a beaming smile across her face.