Big Mouth and Monkey spent the whole day working and brought back several hundred more white poles that could be made into spears, but the adults who had been chopping trees were in a sorry state.
They had worked themselves to the bone all day yet had felled fewer than ten fir trees. They had not even hauled all of them back; several were still lying in the forest. Three of their Stone Axes had also broken.
But Luo Chong mercilessly told them they had to continue tomorrow. However, whoever did the best work would get new equipment.
New equipment? Everyone was baffled. The Stone Axe was already the best tool they had ever seen. What could possibly be more useful than a Stone Axe?
After dinner, everyone began their post-meal entertainment again, while Luo Chong started boiling wax beside the Fire Pit. He put the collected lumps of wax into a pot to melt, skimmed off the impurities with a spoon, and poured it into a large clay mold he had prepared beforehand, letting it solidify again into one whole block of white wax.
He then cut it into small pieces and carved them with a Bone Knife into the shapes of tools, such as axe heads, small hammerheads, Planing Knives, chisels of various sizes, and gripping tongs.
He carefully polished the wax blocks to the exact one-to-one proportions of the real objects. Then he wrapped the wax models in clay, leaving only a small opening, and pressed it tight so the clay fully touched the wax blocks without leaving any gaps.
He then left them to air-dry. Once the clay had dried completely, he heated it over a fire, causing the wax blocks inside to melt again. After pouring out the liquid wax, he had a hollow clay casting mold.
Whatever shape the wax block inside the mold had been, that same shape would be left as a cavity within it. For example, if the mold contained a wax axe head, then after melting and pouring out the wax, an axe-head-shaped cavity would remain inside.
A thin layer of wax would also remain on the inner wall of the mold, which would make it easier to remove the casting later.
The "Lost-Wax Casting" method was somewhat troublesome, but it was relatively precise and did not waste material. The poured-out wax could also be solidified into large blocks again and reused over and over.
The women who collected Insect Wax did not understand either, but they knew the Chieftain truly needed the stuff, so they would simply continue collecting it tomorrow.
Dashu and Lame, however, were a little different. Dashu could tell that these were probably weapons, but he could not understand how something so soft could be used as an axe.
Lame's attention was focused on the clay casting molds. He himself made Pottery, so he thought the molds should also be fired in the flames. Was the Chieftain planning to make weapons out of earth?
Explaining everything to them would have been futile. It was better to let them see the real things for themselves.
Early the next morning, the tribespeople led the Blue Antelope away. After Luo Chong tirelessly drilled the idea into them, they finally understood that beasts could be used not only for food but also to help humans work—and all they needed to pay was grass growing everywhere.
Big Mouth, Monkey, Big Fur, and Second Fur stayed behind. Their task today was to operate Luo Chong's bellows.
The charcoal was ready. Once the heavy wood had burned into black charcoal, it became extremely light. Lame's pottery from the previous day had also been fired, and today he was specifically helping Luo Chong.
Lame was very clever; otherwise, he would never have figured out how to make a harrow on his own. Thus, Luo Chong planned to teach him how to smelt copper. This kind of work could not possibly be done by Luo Chong alone forever, so finding an apprentice was better. Lame, as a disabled man, was the best candidate, since this work did not require running around.
All four furnaces had dried. They lit two of them this time. Big Fur and Second Fur pressed the bellows, while Big Mouth and Monkey loaded the charcoal.
Under the force of the bellows, flames shot high from the furnace mouths. One layer of crushed copper ore and one layer of charcoal were stacked three layers high. The cylindrical furnace chamber held heat very well. Before long, the ore inside had begun glowing bright red, then slowly melted. The molten copper flowed through the gaps to the bottom of the furnace, gathered together, and became a lump of copper mixed with slag.
The Tin Ore beside it was being worked at the same time. It was even faster. Tin Ore had a very low melting point and could melt within minutes under a fierce fire.
Using a branch, they dragged two pieces of metal mixed with many impurities out of the ashes beneath the furnace. Without a blast furnace, things were inconvenient; they could not obtain pure molten copper directly.
They continued adding charcoal and ore to the two furnaces, keeping them at a high temperature and smelting copper without stopping. Luo Chong had personally watched one batch just now, and it had produced only a piece of impure metal the size of a child's fist. It was very slow.
After smelting seven or eight batches for roughly three or four hours, they finally accumulated a pile of impure copper and tin lumps.
The brass ore Luo Chong had brought back this time contained more than eighty percent metal, so they obtained a lot of raw copper. If it had been malachite or azurite, the copper yield would certainly have been lower. The Tin Ore's tin yield was not high either, but tin made up only a small proportion of bronze, so it was enough.
They lit two more furnaces. Once the temperature rose, they placed crucibles made of refractory clay inside and put the raw copper and impure tin into separate crucibles. They increased the heat with the bellows. When the copper and tin had both melted into liquid, the copper's greater density caused the lighter impurities to float on top of the molten metal.
They then used a clay spoon to skim off the surface impurities. However, they did not throw them away. Some copper still remained among those impurities, and once enough had accumulated, they could pile it together and smelt it a second time.
Using the prepared ceramic rods, they carried out the cleaned molten copper together with its crucible, then poured it into a gridded clay mold and left it to cool.
The tin was handled the same way, only faster. Tin melted at just over two hundred degrees, which was why it could be used for soldering circuit boards. Moreover, when copper and tin were mixed together, the alloy's melting point would also decrease.
Lame, his four little companions, and Luo Chong all watched the molten metal in the mold slowly solidify and cool.
They did not understand the principles involved, so they were astonished. They had no idea why stone could be burned into something like water, or why this scalding water became harder and harder as its temperature fell.
Elder had nothing to do today, so he came to observe as well. He wanted to draw everything Luo Chong had done and pass it down to future generations, but copper smelting was simply too complicated. He did not know how to draw it, and so he kept watching with a deeply furrowed brow.
They waited until the copper plates and tin plates were no longer too hot to touch. Luo Chong eagerly poured out all the Metal Plates. It was noon by then, and the still-warm plates reflected dazzling light beneath the sun.
The copper plates gleamed golden, while the tin plates flashed silver. One side was flat, and the other was covered in neat rows of tiny cubes. They were exceptionally beautiful.
Lame, Elder, and the four little companions all gaped at the Metal Plates. They had never seen anything so beautiful, something that could glitter and shine. The rapture on their faces was no less intense than that of modern people seeing gold bars.
Even Qu Bing, who had been playing nearby, was drawn over. He touched this one and examined that one; they were still hot.
"Chieftain, what are these?" Qu Bing picked at the bumps on the copper plate and asked Luo Chong with his head tilted back.
Luo Chong rubbed his head. "This is called copper, and this is called tin. Watch them here. I'll go bring something over."
Qu Bing nodded and softly muttered the words "copper" and "tin" with Lame and the others.
Meanwhile, Luo Chong carried over a pile of tool molds, along with several large, thin clay plates. They had a very shallow groove on top for making rulers, as well as Board Saws.
Luo Chong urgently needed metal tools, so he did not rest and immediately began casting bronze.
He took out a new crucible and put in the copper blocks first. Once they had melted into liquid, he added the tin blocks. Copper had a much higher melting point than tin, so the tin melted within less than a minute of being added. He stirred it evenly with a ceramic rod, and then it was ready to cast.
The first batch was cast into axe heads and hammerheads, though the ratio had been adjusted slightly. The copper-to-tin ratio was five to one and a half—that was, twenty Copper Ingots to six Tin Ingots. Luo Chong was afraid that a five-to-one ratio would not be sharp enough and would also be too soft.
The boiling molten alloy was poured into the molds. A plume of white smoke emerged from the openings left in the casting molds, then a small flame rose, flickered twice, and went out with a puff.
Each day, I examine myself thrice: Did you vote? Did you comment? Did you send a heart? Finally, I'll whisper a plea for a tip—send me a red packet for the New Year, please (super quietly).
Before you continue