When the sun stood in the middle of the sky, the basic form of the smelting furnace was completed.
It was a cylindrical structure that came up to my waist.
The surface was still damp and carried the earthy smell unique to clay.
The smell of wet earth was mixed with the smell of stone.
When the autumn sunlight shone on the surface, the damp clay glimmered faintly.
I touched the smelting furnace with my hand.
A cold, damp sensation came through.
When I pressed my fingers against it, a little clay smeared onto them because it had not yet fully hardened.
The stones embedded in the wall protruded here and there, creating a rough texture, and when I touched it with my hand, I felt stone and clay by turns. The stones were hard and cold, while the clay was soft and damp.
I looked inside.
The interior was hollow.
A circular space had been dug deep within, and the wall surface had been smoothed.
It was Old Man Hot Hands's handiwork.
The places his hands had touched were clearly different. They were much smoother and more even than the rest.
At the bottom, the place where the bellows would be connected had been marked, and a fist-sized hole had been left open.
Ding!
『Smelting Furnace Construction Progress: Stage 1 Complete』
→ Basic Structure Complete
→ Next Stage: Bellows Hole Installation
→ Progress: 35%
The people gathered around the completed smelting furnace and looked at it.
Their faces showed a mixture of wonder and pride.
They seemed unable to believe that they had made something like this with their own hands.
"Wow, we really did it!"
A man shouted in admiration.
He circled the smelting furnace, examining it from every angle, nodding again and again.
"Can we really make a hot fire now?"
"Well, I don't know either."
Another man answered, tilting his head.
"But if the Chieftain says it can be done, then it will surely work."
"That is true. The Chieftain killed a bear yesterday, did he not?"
"Right. He brought down that huge bear with a single strike, so compared to that, this should be as easy as eating cold porridge, shouldn't it?"
"In any case, we must trust the Chieftain!"
Solid Rock spoke firmly.
"If we do not trust the Chieftain, who will?"
"That is true."
"I trust the Chieftain too."
"Me too!"
One man touched the smelting furnace with his hand in admiration, and another circled around it, examining it here and there.
Everyone looked fascinated.
One man even stuck his head inside to peer in, while another tapped the wall with his finger.
"This is truly something I have never seen before."
Running Deer said as he looked up at the smelting furnace.
"I have never seen such a large hearth."
"Rather than a hearth..., hmm. It seems like something different."
Fierce Eyes tilted his head.
"Yes, it looks completely different from an ordinary hearth. To begin with, the shape itself is different. This is the first time I have seen a hearth with walls this thick and an interior this deep."
"Right, the hearths in our village do not look like this."
"Now we need to make the hole."
I pointed to the lower part as I spoke.
"The hole?"
Running Deer asked.
"Yes. We will make a connection hole here."
"A connection hole? Ah, the hole for connecting the bellows?"
I added an explanation.
"Yes. We connect the bellows here and send air inside. The more air enters, the hotter the fire becomes."
"Ah, so that is why the hole is needed!"
Solid Rock nodded.
"But where do we make the hole?"
"Here, at the marked spot below."
I pointed at the location with my finger.
"And the angle needs to be slanted upward. Like this, aimed slightly upward."
I showed the angle with my hand.
I held my palm diagonally, making an angle of about thirty degrees.
It pointed from below toward above.
"Why upward?"
Solid Rock tilted his head and asked.
"Can it not point downward?"
"No."
I spoke firmly.
"Air rises upward and burns the charcoal better. If it points downward, the efficiency drops."
"Ah, I see. But why is it more efficient when the air rises upward?"
"Good question."
I explained with gestures.
"Air has the property of rising when it becomes hot. We use that property. Hot air rises and passes between the charcoal. If we blow wind from below the charcoal, it naturally spreads upward and burns all of the charcoal."
"Then the charcoal burns better?"
Running Deer cut in.
"Yes, exactly."
I nodded.
"The air passes evenly between the charcoal and supplies oxygen."
"Oxygen? What is that?"
Fierce Eyes tilted his head.
"It is something needed for fire to burn."
I explained simply.
"It exists in air, and fire burns because it is there. It is also why fire goes out in a sealed place. If you put fire inside a jar and close the lid, the fire goes out, right? That happens because the oxygen disappears."
"Ah...."
The people exclaimed at the same time.
Their eyes widened.
"So that is why fire grows stronger when you blow wind into it!"
Solid Rock slapped his knee.
"Yes, exactly."
I answered with a smile.
"Solid Rock, you understand well."
"Thank you, Chieftain!"
Solid Rock smiled brightly.
"Then how large should the hole be?"
Fierce Eyes asked.
"About the size of my fist."
I showed him my clenched fist.
"Can it not be larger?"
"No."
I shook my head.
"If it is too large, heat escapes, and if it is too small, there is not enough air. This exact size is proper. Everything has a proper size."
"Ah, I see."
Fierce Eyes nodded.
"That is right."
I picked up a stone knife.
"Now I will make the hole."
I began carefully making the hole with the stone knife.
The clay had not fully dried yet, so the work was easy. The blade slid in smoothly, and clay fell away.
Each time the blade dug into the clay, the smell of damp earth rose up.
"Wow, it goes in well."
Running Deer exclaimed.
"That is because the clay has not hardened yet. Once it hardens, it will not be this easy."
I first carved away a little from the outside, then dug deeper.
Slowly, carefully.
If I dug out too much at once, the hole would become uneven, so I carved it away little by little.
"Chieftain, shall I help you?"
Solid Rock asked.
"No, it is fine. This is precise work, so I have to do it myself. If the angle is even slightly off, the efficiency drops. Even a single degree can change the airflow."
"Ah, I see. Then I will watch from the side."
Solid Rock took one step back. The others also held their breath and watched.
I held the knife diagonally and dug inward.
Maintaining a thirty-degree angle, I put strength into my wrist and pushed at a steady angle.
Lumps of clay dropped away, and the fist-sized hole gradually deepened.
Fifteen centimeters, twenty centimeters, twenty-five centimeters.
I pierced through the thickness of the wall.
As the final lump of clay fell inward, the hole opened.
"It is almost done!"
Running Deer shouted excitedly.
"Be quiet. The Chieftain is concentrating."
Solid Rock scolded Running Deer.
"Ah, sorry. Chieftain, I apologize."
Running Deer scratched his head.
I put my hand in and checked.
I felt all the way inside with my fingers, checking whether the hole was smooth and the angle was right.
Clay smeared onto my fingertips, and the inside of the hole was smoother than I had expected.
"How is it?"
Solid Rock asked cautiously.
"It turned out well. The angle is right, and the size is proper."
Old Man Hot Hands smoothed the edge of the hole beside me.
"The edge must be smooth for the bellows to fit well."
The old man spoke.
"Right. You are correct, old man. If there is a gap, air will leak. If air leaks, efficiency drops."
"I will finish it. I am used to this kind of work."
The old man's fingers moved along the rim of the hole.
He pressed the protruding parts flat and rubbed the uneven places smooth.
His hand movements were as natural as flowing water.
"Old man, your skill is truly excellent."
Running Deer exclaimed in admiration.
"Hardly. This much is basic."
Hot Hands smiled modestly.
"I have handled fire all my life, so my hands move on their own. Before my head thinks, my hands go first."
He tore off small pieces of clay, filled the gaps, and pressed them firmly into place with his fingertips.
He smoothed it until it formed a perfect circle.
His finger circled the rim of the hole once, and finally, he brushed it with his palm.
"Now it is done. Perfect."
Ding!
『Bellows Hole Installation Complete』
→ Air Intake Efficiency: Good
→ Progress: 50%
"We are more than halfway done!"
At my words, the people cheered.
"Already halfway!"
"It is going faster than I thought!"
"We are really doing it! It is thanks to the Chieftain!"
"Right, because the Chieftain is leading us, it is going this quickly."
"Old Man Hot Hands is incredible too!"
The people clapped.
Hope bloomed on their faces.
Even those who had been half in doubt at first now had changed eyes.
"Good. Now we need to dry it."
I spoke while looking at the smelting furnace.
"Dry it?"
Running Deer asked.
"Yes. We cannot light a fire in it like this. First, we have to dry it."
"Why? Can we not light a fire right away?"
"No. If we light a fire while moisture remains, a problem will occur."
"How long must it dry?"
"About two days."
"Two days? That long?"
Running Deer asked in surprise.
"Yes. It has to dry slowly. We must not rush. If we hurry, it will crack."
"Crack?"
Solid Rock asked worriedly.
"Then would we have to make it again?"
"Yes. That is why we have to do it slowly. We do not have time, do we? We cannot afford to make it again."
"Why does going slowly keep it from cracking?"
Fierce Eyes asked.
Perhaps because none of them had any knowledge in this area, they kept asking similar questions.
"If we hurry and light a fire, the moisture, the water, escapes all at once and causes cracks. At first, we have to use a weak fire slowly, then gradually make it stronger."
I pointed to the wall of the smelting furnace as I spoke.
"I see."
Fierce Eyes nodded.
"The water inside the clay must evaporate slowly, but if it evaporates suddenly, the clay contracts and cracks. As the water escapes, empty spaces form. If it escapes slowly, the clay contracts while filling those spaces, but if it escapes suddenly, there is no time to fill them, so cracks appear."
"Ah, so that was the principle."
Running Deer exclaimed in admiration.
"Chieftain, you truly know so much."
"The ancestors taught me."
I tapped the wall with my finger.
There was still a lot of moisture, so the sound was dull.
Dry clay made a clear sound, but wet clay killed the sound.
"What do you think would happen if we lit a strong fire in it now?"
I asked while looking around at the people.
I intended to plant knowledge in them by asking questions like this.
"Since you said it would crack, Chieftain, I think it would crack."
Solid Rock answered.
"Yes. But do you know why it cracks?"
"Because the moisture escapes?"
Running Deer answered.
"Yes, that is right. But more precisely, when water becomes water vapor, its volume increases."
I explained with gestures.
"Then the clay tries to expand, but the outside has already hardened. That is why it cracks. The inside pushes outward, but the outside does not stretch, so it bursts."
"Ah...."
The people nodded.
"So we have to dry the inside and outside slowly at the same time. There must not be a difference in temperature. If only the outside dries while the inside remains wet, a problem occurs."
Hot Hands slapped his knee in admiration.
"As expected of the ancestors' wisdom! I have handled fire all my life, but this is the first time I have heard such a clear explanation."
"Have you had a similar experience too, old man?"
I asked.
"Yes. Long ago, I once made a hearth in a hurry, and it collapsed."
Hot Hands nodded.
"That was truly disastrous."
"What happened?"
Running Deer asked with curious eyes.
"Something I had spent three days making collapsed in an instant."
Hot Hands sighed as he spoke.
"It was truly difficult then. All the materials were wasted, and all the time was wasted as well."
"What did you do after that?"
Solid Rock asked.
"From then on, I always dried things slowly."
Hot Hands answered.
"But to think there was such a principle. Only now do I understand why that happened. It is thanks to you, Chieftain."
"You had learned it through experience and already knew it, old man."
I nodded.
"Your experience was the correct answer."