With a crisp sound of "whoosh," the high-quality charcoal was fed into the furnace, and the air passed through the tunnel, sneaking in through the ash holes. Soon, a fiery orange glow ignited.
With mixed emotions, Han Cheng personally poured two jars of crushed mineral powder into the large vat, about thirty pounds in total.
Thus, the great endeavor of copper smelting in the Green Sparrow Tribe began.
The thermal conductivity of ceramics is far worse than that of metals. Still, Han Cheng couldn’t create a steel furnace or any other more heat-resistant and thermally conductive metal furnace, so he had to make do with a ceramic vat.
"Add more charcoal and bring the bellows over," Han Cheng ordered after waiting for a while, seeing that the mineral powder in the ceramic vat hadn’t melted much.
The "hand pump" was pressed up and down, turning the fan back and forth, forcing air through the ceramic tube and into the furnace.
Before long, the furnace blazed with intense flames, much fiercer than before, with the central charcoal glowing a whitish red.
These efforts paid off. After about thirty minutes, Han Cheng noticed that the mineral powder in the ceramic vat had lowered slightly.
Sweating from the heat, Han Cheng couldn’t help but show a delighted expression. He hadn’t expected such a gratifying result on his first attempt at smelting copper ore.
Shaman also leaned over, stretching his neck to peer inside. His face also broke into a smile. Although he couldn’t discern much, it didn’t stop him from sharing Han Cheng's joy.
The senior eldest brother and the others building the shelter around the furnace also came over to watch. They were amazed at the transformation of stone into liquid.
Imagining a future with an abundance of metal tools in the tribe, they were filled with renewed energy. After watching for a while, they returned to building the shelter even more enthusiastically.
As time passed, more and more mineral powder melted, eventually turning into a thick, dark red metallic liquid.
Emboldened by the sight, Han Cheng suddenly stopped feeling happy. At this moment, he realized that he had overlooked something very important.
That was, how to extract the molten metal from the large vat.
Usually, it would be best to open a hole at the bottom of the ceramic vat so the molten metal could flow out by itself, but that wasn’t possible right now.
Han Cheng tried to scoop some with a wooden-handled ceramic ladle, but seeing the metal beads drip unevenly, he abandoned using the ladle.
After thinking for a moment, he ordered the fire to be stopped, and no more charcoal should be added to the furnace, nor should the bellows be pumped.
As the furnace temperature dropped, the bright red molten metal started turning dark red and eventually solidified back into a solid form.
Shaman, who had come over to look, grinned widely, and the senior brother and others also smiled broadly.
Because the ceramic vat now contained a large chunk of metal, which appeared somewhat black, resembling iron.
After so long in the tribe’s search for iron bacteria, the amount of iron they had obtained was minimal. But this metal vat appeared to contain more than all the iron tools the tribe had combined, making them incredibly happy.
They were excited, but Han Cheng couldn’t share their joy because, in his memory, copper didn’t look .
No matter how he looked at it, the metal before his eyes seemed to resemble slag.
Han Cheng couldn’t help but sniffle. He realized he had made another serious mistake—he hadn’t separated the copper liquid from the slag.
The two could not be separated, so extracting pure copper became difficult.
After waiting longer for the temperature to drop further, Han Cheng instructed them to lift the large vat off the furnace.
They turned it upside down and struck it a few times, but seeing that the solidified mixture of copper and slag inside hadn’t fallen out, Han Cheng ordered them to smash the vat.
The tribe didn’t have a Sima Guang (a historical figure famous for smashing a vat to stop a flood), but they were just as efficient and decisive when it came to smashing vats.
The people, invigorated by the metallic success, followed Han Cheng’s orders, and in no time, they smashed the sturdy vat into pieces.
Then, the contents inside were freed.
The contents resembled the bottom of a vat—cylindrical, with purple metal at the bottom and black, loosely textured slag at the top.
The purplish metal was the refined pure copper.
Han Cheng found a stone and smashed it for a while. While he managed to break some of the slag off, it was impossible to completely separate the slag from the copper using this method.
He would have to act while they were still liquid to separate the two properly.
After looking at it for a while with some regret, Han Cheng didn’t dwell on this failed attempt too much because he hadn’t expected to succeed on the first try.
Moreover, the copper smelting wasn’t without its gains. Han Cheng learned two important things: that the large vat needed a hole at the bottom and that slag was lighter than copper and would float on the molten copper once melted.
Separating the slag from the copper would be much easier with these discoveries.
"Divine Child, here!"
The third discovery came soon after, and it was still a shortcoming.
Hei Wa pointed at the furnace and spoke to Han Cheng.
As the charcoal fire died down, the furnace gradually cooled.
Han Cheng followed Hei Wa's direction and looked inside the furnace. He saw that many of the bricks had fused, the surface smooth, and when touched, they felt like porcelain tiles.
This was caused by the high temperature inside, which caused the bricks to slowly melt and then harden again as they cooled.
"Take this furnace apart!"
As Han Cheng touched the smooth bricks, his face suddenly paled because a terrifying scenario came to mind—
With the charcoal continuously burning, the bricks that made up the furnace gradually melted, becoming softer and softer, until they couldn’t withstand the weight above and crumbled.
If the large vat containing molten metal were to tilt and fall, the molten metal, still at terrifyingly high temperatures, would spill out and land on someone...
Just imagining such a horrifying scene sent shivers down his spine, especially after he had stood beside the furnace for a long time.
The people around Hei Wa didn’t understand why the Divine Child wanted to dismantle this perfectly good furnace. The situation seemed incredible to them, as not only did it look better, but the whole furnace seemed sturdier.
However, their confusion lasted only a short time. After hearing Han Cheng describe the terrifying scene, they no longer considered it a good thing.