Time: Winter, C.E. 59
Nine years and nine months old, Nangong Wentian stood in a corner of the orphanage's backyard, facing a pile of miscellaneous items.
Firebricks—salvaged from an abandoned boiler room, their surfaces blackened but overall still intact. An old iron drum—given by Uncle Tanaka, originally used for cooking oil, cleaned out, perfect for the furnace body. Charcoal—bought from the village, cheap, with a high enough burning temperature. And a heap of odds and ends scavenged from the junkyard—an old bellows, broken iron pipes, rusty wire.
Xiao Guang squatted nearby, looking at the pile and scratching his head. "Wentian, what are you planning to do with all this?"
"Build a furnace."
"A furnace?" Xiao Guang pointed toward the kitchen. "Isn't there a stove in the kitchen?"
Nangong Wentian shook his head. "That stove doesn't get hot enough."
"Why do you need such high heat?"
Nangong Wentian didn't answer. Instead, he pulled a crumpled piece of paper from his pocket and spread it on the ground. On it was a complex schematic—furnace body, flue, bellows connection, temperature measurement port, each part labeled with dimensions and notes. It was a design he had finalized last night after drawing all night with the "Star Core."
Xiao Guang leaned in to look. Though he couldn't understand the annotations, he could tell it was an impressive design.
"This is…" he asked.
"A Smelting Furnace," Nangong Wentian said, pointing at the drawing. "It can melt metal."
Xiao Guang paused for a moment, then his eyes lit up. "Like on TV, where they turn iron into liquid?"
"More or less."
Xiao Guang got excited and rolled up his sleeves. "Then I'll help!"
The two of them got to work.
The first step was clearing the ground. This corner of the backyard was usually deserted, overgrown with weeds and littered with rubble. It took them a whole afternoon just to clear the area.
The second step was building the furnace body. Nangong Wentian stacked the firebricks one by one, forming a cylindrical furnace chamber. Xiao Guang handed him bricks and mixed mortar beside him, happily busy.
"Wentian," Xiao Guang asked while passing bricks, "how do you know how to build a furnace?"
"I read it in a book," Nangong Wentian replied without looking up.
Xiao Guang pouted. "Books again. I've memorized that line by now—it's always a book I haven't read."
Nangong Wentian didn't respond and continued stacking bricks. He couldn't say it was from the UC Era Metallurgy Handbook stored in the "Star Core," nor could he say that knowledge came from another world. "Books" were the best excuse.
Once the furnace body was built, the next step was installing the bellows and flue.
The bellows were an old item scavenged from the junkyard; the leather diaphragm was torn, but the frame was still usable. Nangong Wentian made a new diaphragm from an old piece of leather and reinforced it with wire, making it barely functional.
The flue was assembled from several broken iron pipes, secured to the wall with wire, with the other end extending from the backyard into the open space outside.
Finally, installing the temperature measurement device. This was the hardest part—he needed to know the exact temperature inside the furnace, otherwise, the smelting process would be uncontrollable.
He used an old thermocouple—scavenged from a junkyard, said to be stripped from some industrial equipment—connected to a small circuit he had soldered himself, then linked to an old multimeter. This way, when the thermocouple was inserted into the furnace chamber, the multimeter would display the corresponding temperature.
Crude, but functional.
After three full days of work, the smelting furnace was finally assembled.
Nangong Wentian stood before the furnace, inspecting every part. The furnace body was sturdy, the flue was clear, the bellows were powerful, and the temperature measurement device was functioning normally.
"Ready to test," he said.
Xiao Guang nervously swallowed: "Now?"
"Now."
Nangong Wentian filled the furnace chamber with charcoal and lit the fire. Once the charcoal was burning brightly, he placed a small crucible inside—also scavenged from a junkyard, said to be discarded from some laboratory, made of refractory material, just right for use.
Inside the crucible were the materials he had prepared: some scrap aluminum, stripped from old appliances; and a small packet of copper powder, bought from Yamada.
Aluminum-copper alloy. This was the simplest alloy, with a low melting point and easy to make. If he couldn't even manage this, there was no point thinking about titanium alloy.
The charcoal burned brighter and hotter, and the temperature inside the furnace chamber rose steadily. Nangong Wentian stared at the multimeter, watching the needle slowly climb.
500 degrees. 600 degrees. 700 degrees.
The melting point of aluminum is 660 degrees. There.
He peered through the furnace opening and saw the aluminum inside the crucible beginning to melt, turning into a silvery-white liquid.
"It's melting!" Xiao Guang whispered excitedly, "Wentian, look, it's melting!"
Nangong Wentian didn't let himself get distracted, continuing to monitor the temperature. 800 degrees. 900 degrees. The aluminum had completely melted, with a layer of oxidized slag floating on the surface.
Time to add the copper powder.
Using a long-handled iron spoon, he carefully sprinkled the copper powder into the molten aluminum. As soon as the powder made contact, white smoke billowed out, accompanied by a sizzling sound.
Then he picked up an iron rod and stirred it inside the crucible. The molten aluminum was thick, making stirring difficult, but he had to mix it evenly, or the copper would settle at the bottom.
After stirring for five minutes, he stopped and checked the temperature—950 degrees, perfect.
"Done." He extinguished the fire, used iron tongs to lift out the crucible, and poured the molten aluminum into a pre-prepared mold.
The aluminum liquid steamed as it slowly cooled. Ten minutes later, it solidified into a silvery-white metal block.
Nangong Wentian waited for it to cool completely, then picked it up and examined it carefully.
The surface was rough and pitted, with some areas blackened and others riddled with pores. He tapped it with his finger—the sound was dull, unlike the crisp ring of good-quality metal.
It had failed.
He set the metal block aside and rechecked the furnace. The temperature was fine, the timing was fine, the stirring was fine…
What went wrong?
"Star Core." He needed the help of the "Star Core."
That night, after everyone had fallen asleep, Nangong Wentian slipped into the back kitchen and activated the "Star Core." He input the experimental data from the day—material ratios, heating temperature, holding time, cooling speed—leaving out no detail.
The cursor on the screen blinked for a long time—the crude CPU's processing speed was still painfully slow. Nangong Wentian waited a full ten minutes before the results appeared:
Failure Analysis:
Insufficient purity of raw materials: The scrap aluminum contained a large amount of impurities, causing the alloy composition to deviate.
Poor oxidation control: The oxide film on the surface of the molten aluminum was disrupted, absorbing oxygen from the air.
Inadequate Mixing: Copper powder not fully dissolved, localized segregation observed.
Improvement Suggestions:
Use higher purity raw materials.
Add a Covering Agent to prevent oxidation.
Extend mixing time and increase mixing speed.
Nangong Wentian stared at the suggestions, lost in thought.
Higher purity raw materials. Where to find them?
He remembered the batch of old appliances Xiao Guang had scavenged from the junkyard last time. Where did those appliances come from? Yamada had said they were bought from a bankrupt electronics factory, containing many parts with rare metals.
Perhaps, within those parts, lay what he needed.
The next day, Nangong Wentian found Xiao Guang: "Are those old appliances you picked up last time still around?"
Xiao Guang was momentarily stunned: "Yeah, they're all piled up in the corner of the back kitchen."
"Take me to see them."
The two went to the back kitchen and opened the old wooden crate. Xiao Guang dug out a plastic bag from the very bottom, filled with various parts salvaged from the old appliances—circuit boards, transformers, motors, capacitors...
Nangong Wentian examined them one by one. Soon, his gaze settled on a small transformer.
The transformer's coils were made of copper wire, of high purity. The iron core was silicon steel, high in silicon content, usable.
He fished out a few capacitors. Their casings were aluminum, likely of decent purity. There were also some resistors containing trace amounts of rare metals.
"These," he pointed at the pile of parts, "could be a huge help."
Xiao Guang scratched his head: "What can these scraps do?"
"Refinement," Nangong Wentian said. "Extract the metals inside."
For the next few days, Nangong Wentian embarked on another task—refining the raw materials.
He stripped the copper wires, cut them into small pieces, and cleaned the insulating varnish off their surfaces with hydrochloric acid. Then he melted them into copper ingots, repeating the melting process several times to remove impurities.
The aluminum casings were treated similarly. He first sanded off the oxidized layer on the surface, then melted and cast them into small aluminum ingots.
The hardest were the parts containing rare metals—resistors, capacitors, integrated circuits. He needed to crush these things and extract the rare metals using chemical methods.
Without professional chemical reagents, he could only use the most rudimentary methods—acid soaking, alkali boiling, filtering, precipitation.
After countless failures, on the fifth day, he finally extracted a tiny amount of silver-gray powder.
It contained trace amounts of vanadium, chromium, molybdenum—precisely the trace elements he needed.
"Success," he stared at that small pinch of powder, letting out a long sigh.
Xiao Guang watched from the side, his expression complex: "Wentian, you haven't slept these past few days, have you?"
Nangong Wentian didn't answer. He truly hadn't slept properly for several days. His eyes were bloodshot, his face dusty, like a young laborer crawling out of a coal mine.
"It's worth it," he said.
Hunter x Hunter: Starting from Sun Breathing