After befriending Cheng Qin, Du Heng clearly understood this: Xiaoyao Tower could gather wealth, and Gezhi Institute could establish his reputation.
If he did not produce at least one “hardcore” achievement that was enough to shock the court and benefit the ten thousand people, Gezhi Institute would ultimately be a castle in the air and could not escape being crushed by the powerful and wealthy.
And the first cornerstone of Gezhi Institute was… glass.
Ever since the Qujiang appointment, he had been secretly trial-producing it. Western Regions glass was beautiful, but it cost as much as gold, so commoners balked at it. Du Heng did not believe that human craftsmanship could not seize what Heaven made, so he studied The Kaogong Ji and Qimin Yaoshu every night, and he also combined it with the mineral data accumulated by Gezhi Institute to boldly abandon the Western Regions lead-barium system… this method melted easily, but the color was muddy, it cracked easily, and it was poisonous.
“I switched to quartz sand, plant ash, and saltpeter to form a sodium-calcium system,” he told Old Zhou, his eyes shining with light beyond his era. “Only when it transmits light like water, is hard without being brittle, and is non-toxic and harmless can it be used by the people.”
Old Zhou did not understand “sodium-calcium,” but he knew that if this thing succeeded, it would definitely shake Chang’an… because it would break the Hu merchants’ hundred-year monopoly and turn “glass” from a luxury into an everyday item.
Du Heng personally went to Zhongnan Mountain and trekked through every stream valley to find high-purity quartz sand. He also ordered A Ruan to go through the Chang’an wards to collect plant ash from a hundred households and pick the ones with the strongest alkalinity… 70% locust tree ash and 30% mulberry tree ash, with a precise ratio. As for the saltpeter, he bought it from scraps from the Armaments Directorate, which both saved costs and gained the military’s tacit approval.
At Kiln 8, the sample was finally made.
A glass cup lay quietly on the table, crystal clear, gleaming in the sunlight, without a single bubble and without the slightest trace of impurity. Changle held the cup up to the moon and softly sighed, “This sheen is ten times better than the Western Regions.”
Du Heng shook his head, though. “A sample is useless, and mass production is what matters.”
He knew full well that mass production needed to break through three barriers: raw material purity, furnace temperature control, and cost compression.
Thus, at Kiln 9, he test-fired for mass production.
He built a new kiln in the eastern corner of Gezhi Institute and used a pulley system to feed materials to save manpower. He used water-powered bellows to control oxygen and stabilize the flames. He even used a self-made “thermometer” to monitor temperature… this embedded metal wires with different melting points, such as copper, tin, and lead, into ceramic pipes, and by observing the order in which they melted, he could tell how high or low the furnace temperature was.
For three days and three nights, Du Heng guarded the kiln without sleep and did not even remove his clothes. Old Zhou urged him to rest, but he only said, “The success or failure of one kiln is tied to the lights of ten thousand homes.”
On the day the kiln was opened, the morning light had just begun to shine. Inside the box lay thirty glass cups, quiet and still, clear throughout, like congealed ice and like autumn water.
“It succeeded!” Old Zhou wept with joy, knelt, and kowtowed.
Du Heng remained as calm as ever. “What is the cost?”
“Each one uses 100 wen in materials, and the wages are 50, for a total of 150 wen,” Old Zhou calculated.
“Too expensive,” Du Heng said as he shook his head. “For Commoners’ Day use, it needs to be pressed down within 100 wen.”
He immediately improved it.
– He crushed the quartz sand more finely, and the smelting time decreased by 20%.
– He switched plant ash to a unified formula to avoid impurity fluctuations.
– He added a clay insulation layer to the outside of the kiln furnace, saving 30% of firewood and making the fire temperature more stable.
At Kiln 10, the cost dropped to 92 wen.
“It can be sold for 100 wen, and the people can afford it,” Du Heng finally smiled… his smile, like the first light of glass, was clear and resolute.
On the day of the first sale, Zheng Liwan came to the door.
She brought account books with her, and when she saw the glass cup, she cried out in shock, “This thing… can actually transmit light as if there is nothing there?” She took a cup and held it up to the sun, and the bright spot was clear like a mirror, and it could even focus light to start a fire.
“If it is used for a lampshade, reading at night will not hurt the eyes!” Her eyes flashed with sharp light as she said, “Children can read, craftsmen can work at night, and merchants can do their accounts… this is the light of civilization!”
Du Heng nodded. “That is exactly my intention, and the next step is to make glass lamps, mirrors, and a telescope.”
Zheng Liwan immediately offered three strategies.
– Zheng Family Trading Company would exclusively buy the first batch of 1,000 pieces and sell them to Luoyang, Yangzhou, and Liangzhou.
– She would set up a “civilian glass workshop” that specialized in cups, plates, and lampshades, starting at 100 wen.
– She would also set up a “royal glass workshop” to finely make bottles, mirrors, and telescopes for the palace and nobility.
“The profits are split 50–50, you provide the technology, and I provide the channels, manpower, and logistics,” she said. “I trust you because you never deceive the people.”
Du Heng pondered for a moment. “If the royal workshop is established, can we ask His Majesty to bestow a name?”
Zheng Liwan smiled. “I already asked Changle to have an audience, and when His Majesty heard the four words ‘transmits light like water,’ he was delighted.”
Three days later, the imperial edict arrived.
Li Shimin personally wrote: “Approved for Du Heng to establish a royal glass workshop, and granted ten mu of land by the Qujiang bank, thirty craftsmen, and three years of tax exemption. All glass produced by Gezhi Institute must not be imitated by the Armaments Directorate or the Directorate of Imperial Works, and violators will be treated as stealing state instruments.”
What surprised Du Heng even more was that Cheng Chumo brought a secret letter from the Armaments Directorate. “Father Marshal said that if glass can be made into a telescope to observe enemies from ten li away, the border army is willing to purchase all of them, and the first batch will be one thousand units!”
The first launch event was held in Xiaoyao Tower’s Tiangong Hall.
Du Heng invited three hundred Chang’an celebrities, Hu merchants, scholars, and craftsmen to witness it together.
He demonstrated on the spot.
– When a glass cup held wine, it was so clear you could see the bottom, and even tiny dust in the wine could be clearly seen.
– When a glass lampshade covered a candle, the brightness doubled and the whole room became like daytime, and the scholars cried out, “No worries about reading at night!”
– He even used two convex lenses to make a simple telescope, and when he looked at willow leaves on the other side of Qujiang, their veins were clearly visible.
The Hu merchant Abbas knelt on the spot. “This is a divine object, and the Persian King is willing to trade ten fine horses for one!”
The scholars also scrambled to order lampshades. “The imperial examination is near, so with this lamp, what is there to fear about failing?”
Orders flew in like snowflakes.
Within three days, orders for the civilian workshop exceeded five thousand pieces, and the royal workshop received three hundred sets of palace orders, and even Gaoyang ordered twenty military-use telescopes.
Du Heng set iron rules, though.
– Civilian workshop products must start at 100 wen and must not be price-gouged.
– Royal workshop items must be engraved with the seal script stamp “Made by Gezhi Institute” to prevent counterfeits and ensure authenticity.
– All craftsmen were granted profit-sharing for technology… anyone who improved the process could enjoy three years of profit sharing.
Old Zhou sighed. “This method makes craftsmen willing to think, willing to create, and willing to pass it on, and they are not slave labor.”
Changle personally came to the workshop.
Holding a glass cup in her hand, she softly said, “You once said you would use glass as the betrothal gift, and now… it has already lit up ten thousand homes.”
Du Heng stared at her, his gaze blazing. “When Gezhi Institute is established and the steam engine roars, I will use iron wheels as the gift and marry a princess.”
Changle’s eyes shimmered, and her smile was like spring. “I will wait for you, and not only as your wife, but also as your fellow traveler.”
Late at night, Du Heng stood before the new kiln.
The furnace fire lit up his sixteen-year-old face, resolute as iron. In the distance, the craftsmen were carrying quartz sand, the water-powered bellows hummed, and under the glass lamp, apprentices were drawing telescope blueprints.
He knew that glass was only the beginning.
Penicillin would save ten thousand lives, metallurgy would cast new armor, a paddle steamer would connect the seas and frontiers, and the steam engine would open the door to industry… and the long scroll of gewu was slowly unfolding.
And that ray of transparent light rose from a 100-wen glass cup and would eventually illuminate the industrial dawn of Great Tang…
It was not in miracles, but in gewu, and it was not in Heaven’s gifts, but in human effort.
Deep within the lamplight, the youth stood with his hands behind his back and quietly waited for dawn.