The blacksmith shop remained unlocked all night.
Jenny Huang threw her usual heavy iron-smashing hammer into the corner, replacing it with a three-inch carving knife, a fine-tooth file, a beef-tendon bow saw, and several brass needles thinner than hairpins.
The scene looked incredibly bizarre.
A group of burly artisans, accustomed to forging armor, horseshoes, and mechanical contraptions, crowded around the worktable.
Yet no one dared to breathe too heavily, afraid that a strong exhale might blow the thin brass sheet off the table.
At this moment, Jenny Huang sat cross-legged on a low stool. Pressing down on the copper sheet, she meticulously traced lines with the carving knife in her right hand.
She had always possessed a fiery temper; when swinging her hammer, she could wake up half the street.
But when it came to delicate work, she became a completely different person.
An old artisan nearby held back for a long time but finally couldn't resist muttering softly.
"Manager Huang, since when did our blacksmith shop turn into an embroidery parlor? If we take this thing to the battlefield, who could it possibly poke to death?"
Jenny Huang didn't look up; her carving knife continued to move.
"It might not poke the Helian cavalry to death, but it can certainly poke your ancestral stupidity to death."
The old artisan choked and shrank his neck, while the apprentices held back their laughter so hard that their shoulders shook.
Su Mu was even more restless on the other side.
The three cloth bags he had brought from Sunset Valley were all open.
White quartz, plant ash, and shell powder were divided into small piles and sifted through a fine sieve over and over again. The resulting sand was so fine it could stick in the grooves of a fingerprint.
He poured the sand into the crucible, added ash to adjust its properties, and then added shell powder to stabilize its structure, muttering process names that no one else could understand.
"If the fire is too fierce, the sand will trap bubbles. If the fire is too soft, the material won't melt thoroughly."
"Seal the furnace opening by half an inch, leave three fingers of space at the draft door. Don't let any ash fall in; one grain of ash means one blind spot in the mirror."
The apprentice tending the furnace wore a bitter expression.
"Valley Master Su, is the half-inch you mentioned based on your hand or mine?"
Su Mu looked up and glared at him.
"No matter how long your hands are, can half an inch grow into a foot?"
Jenny Huang threw a remark from the table.
"Stop bullying my apprentice. If you ruin that crucible, don't blame me for stuffing you into the bellows to use as a leather bag."
Su Mu rolled up his sleeves and guarded the furnace himself, the firelight illuminating his face with a red glow.
...
When the first batch of material came out, everyone crowded around.
The melted lump of glass material was pulled out with iron tongs and pressed into a small blank while hot.
Its color was much more translucent than ordinary colored glaze, but when Jenny Huang held it up to the lamp, her brows knitted together.
"There are bubbles inside."
Su Mu leaned in to look and indeed saw tiny air bubbles hidden in the core of the material, like grains of rice buried in jelly.
Jenny Huang tossed the material into the waste basket.
"Trash."
Su Mu's face twitched.
"It can still be ground."
"Grind my foot. The light is already distorted here; making it will only deceive yourself."
For the second batch, the fire temperature was steadier, but fine sand lines appeared on the edges of the material.
For the third batch, the material was clear, but it cracked during annealing.
By daybreak, seven or eight pieces of scrap material had piled up in the waste basket. No one in the blacksmith shop joked anymore; even the previously loud-mouthed old artisan kept his mouth shut tight.
This work was wicked.
When forging a sword, if the iron was disobedient, hammering it hundreds or thousands of times could always force it into shape.
But this tiny mirror blank couldn't be hammered, couldn't be struck, and especially couldn't be rushed.
If the heat was off by even half a finger's width, the entire first half of the night's effort turned to garbage.
In the afternoon, Xu Qinghuan arrived at the blacksmith shop.
She didn't have anyone announce her arrival. When she entered, she caught Jenny Huang holding a half-finished ground lens up to the window.
The center of the lens was already bulging, and the edges had thinned out, but when looking at the carved lines on the table through it, the lines became distorted and twisted into strange shapes near the edges.
Su Mu's eyes were red. Spread out beside his hand were over a dozen sheets of paper recording temperatures and grinding times, covered in dense writing.
Jenny Huang placed the lens back on the velvet cloth, cursing through gritted teeth.
"The middle is okay, but the edges are a complete mess. This isn't a mirror; it's a scam."
"The pressure is uneven where the edge is thin. Once the grinding disc presses down, the outer ring takes the sand first. No matter how I adjust it, it's always skewed."
An old grinder transferred from the Directorate of Armaments stood nearby, sounding a bit guilty.
"Lord Xu, this task shouldn't have been given to a blacksmith in the first place. Grinding mirrors relies on ancestral techniques."
"Manager Huang knows how to forge iron, but glaze is delicate. How can it be handled with a file's temper?"
Jenny Huang looked up, her anger already reaching her brows.
"And what has your ancestral technique managed to grind out?"
The old grinder lifted his chin.
"At least it wouldn't produce such distorted, bizarre lenses."
Su Mu was about to speak, but Xu Qinghuan raised her hand to stop him.
She walked to the table, picked up the half-ruined lens, and asked Li Sheng to bring a bowl of clear water.
The crowd didn't understand her intentions. They only saw her use a bamboo skewer to pick up a drop of water and let it fall onto an extremely thin piece of glaze.
The water drop didn't scatter. It rested perfectly round on the glaze surface. As light passed through it from the side, the fine lines on the table were actually magnified a bit.
The old grinder's sneer caught in his throat.
Xu Qinghuan pointed at the water drop.
"Do you see? When water falls on a flat surface, it naturally gathers to be thick in the middle and thin at the edges."
Jenny Huang's eyes instantly lit up, and her hand had already reached for a charcoal pencil.
Su Mu lunged forward half a step, almost knocking over the water bowl.
"The water's surface naturally rounds itself!"
Xu Qinghuan looked at the half-ruined lens.
"You are using a hard disc to grind a hard blank, so it's difficult to apply even pressure on the outer ring. Since that's the case, why not borrow the nature of water first?"
She took a piece of paper and drew a shallow concave disc.
"Make an extremely flat copper disc, polish the surface until it's bright, then mix fine powder with glue, and let the mirror blank spin while resting on the water film. The water will distribute the pressure evenly, preventing the outer ring from taking the sand first."
Jenny Huang chimed in.
"We'll also make a soft support, three layers."
"Copper disc on the bottom, water glue in the middle, and thin wax on top. The wax won't touch the mirror surface; it will only protect the edges."
Su Mu slapped the table.
"The grinding powder needs to be changed too. River sand won't do. We must use quartz powder, starting coarse and then going fine, and finally use mussel powder and deerskin to polish it."
The old grinder opened his mouth, still wanting to mention ancestral rules.
Jenny Huang had already shoved the half-ruined lens into his hands.
"Mr. Ancestral, come on, grind a non-distorted one for me to see."
The old grinder's hands stiffened, and after a long while, he squeezed out a sentence.
"My hands are sore today."
Li Sheng was highly amused beside them.
"Your hands are sore at just the right time, but your mouth is certainly hard."
The oppressive atmosphere that had hung over the blacksmith shop for half the day dissipated instantly. The apprentices lowered their heads to work, their shoulders shaking even harder.
Xu Qinghuan didn't stay much longer, only leaving one instruction before she departed.
"Within three days, I want an instrument that can observe water samples."
Su Mu and Jenny Huang agreed simultaneously.
From then on, the blacksmith shop truly became a living hell.
...
Lao Sun, having heard from somewhere that the blacksmith shop was building an instrument "capable of seeing demons clearly," arrived the next day holding his rice bowl.
He squatted by the threshold, shoveling porridge into his mouth while staring at the mirror blank in Su Mu's hand.
"Can it really see demons?"
Su Mu didn't even look up.
"It can't see demons, but it can see living creatures smaller than lice eggs."
Lao Sun's hand paused.
"Isn't that exactly a demon?"
Jenny Huang was so amused she almost filed the copper ring crooked. She kicked a piece of wood shaving over.
"Lao Sun, just eat your food and stop scaring the apprentices here."
Not only did Lao Sun not leave, but he also came every day after that.
At noon on the third day, the lamp oil in the blacksmith shop had already been replaced four times.
When the final lens was taken off the deerskin, no one in the room spoke.
Su Mu washed it in clear water and then supported it with a soft cloth.
Light passed through the lens and fell onto the white paper; the edges had no distorted shadows, and the center was cleanly bright.
Jenny Huang looked down at it for a long time.
"It's done."
Su Mu took out the second one and placed it alongside. Two tiny convex lenses lay on the velvet cloth.
Clear, perfectly round, with beautifully finished edges, they looked like two star-pearls plucked from the Milky Way.
The old grinder was also there; looking at the velvet cloth, his face flushed red, and he finally lowered his head.
Jenny Huang, however, did not let him off the hook.
"An ancestral heirloom, care to critique it?"
The old grinder's lips moved a few times.
"Manager Huang's craftsmanship... I concede."
Jenny Huang placed her file onto the table.
"You shouldn't submit to me, but to Lord Xu's drop of water."
When Xu Qinghuan arrived, the microscope stand was already set up.
The brass tube was not large, polished to a brilliant shine all over.
The wooden frame was made of hard jujube wood, the stage could actually be raised and lowered, and there was a small round mirror underneath to direct the light.
Su Mu held the two lenses, his fingers trembling, though his mouth remained stubborn.
"I am not shaking. This is just from staying up all night."
Li Sheng looked at him.
"You had better save those words for when Lao Sun checks your pulse."
...
An incense stick's time later.
"It is done."
Xu Qinghuan was in no hurry to look. He merely had someone fetch a thin piece of glass and told Li Sheng to draw water from the well.
Li Sheng ran off swiftly.
Xu Qinghuan picked up a single drop from the water and placed it on the thin slide.
Then he covered it with an even thinner piece of glass and placed it in the center of the stage.
Su Mu stood before the lens tube, his entire demeanor falling completely quiet.
Three days and three nights of furnace fire, scrap materials, and arguments.
Relying on that drop of water, everything was pressed into this one-inch brass tube.
Lao Sun finally could not hold back and urged him in a low voice.
"Look, Valley Master Su. Whether the demons are there or not, you must at least give this old man a definitive answer."
Su Mu bent down and brought his eye to the eyepiece.
The water drop spread out between the glass slides, the murky well water lying quietly on the stage.
In the next breath, Su Mu's hand froze beside the tube.
