The Ming Dynasty: My sister, Empress Ma

Finally, Ma Wenyuan arranged for the two brothers to work with Fang Xiaoru to take notes.

Fang Xiaoru's lips twitched.

He knew Ma Wenyuan was teasing him about his status as a scholar, but he still nodded respectfully.

"Yes, sir."

So from that day onwards.

The backyard of the Imperial Brother-in-Law's residence was transformed into a bustling glass testing ground.

In the first experiment, the ingredients were put into the furnace and the temperature was raised to 1400 degrees Celsius.

After burning for four whole hours, the liquid in the crucible finally melted.

Ma Wenyuan dipped a small amount of water into an iron pipe, blew a small bubble, and waited to see the effect.

After the initial shock subsided, everyone fell silent.

The glass was indeed clearer than ordinary glass, but it still had a distinct green tint, with dense bubbles, like frozen caviar.

Looking through it is like looking through a layer of dirty water.

"Why?" Zeng Xiu reluctantly calculated the proportions in her notebook.

"Ten pounds of quartz sand, three pounds of wood ash, half a pound of limestone... That's right."

Xu Miaoyun used a small hammer to break the glass, and countless tiny air bubbles and unmelted sand particles could be seen on the cross-section.

Xu Miaoyun pondered for a while, then held the glass up to her eyes and examined it again and again.

"Teacher, is the temperature not high enough?"

After a moment's thought, Ma Wenyuan nodded.

"Miaoyun hit the nail on the head."

"The temperature is indeed not high enough. Our kilns can only reach 1,400 degrees Celsius at most, but for the quartz sand to be completely melted and clarified, it is best to reach 1,550 degrees Celsius or higher."

"With a difference of more than 100 degrees, the viscosity of the liquid is too high, the air bubbles cannot be released, and the sand particles cannot be completely dissolved."

"What should we do then?" Zeng Xiu asked, somewhat discouraged.

"You can't exactly add fuel to the fire in the kiln, can you?"

Zeng Qing stood silently to the side.

To be honest, he couldn't understand any of this stuff.

However, Zeng Qing has one advantage: he strictly follows Ma Wenyuan's instructions without any doubt.

Ma Wenyuan didn't say anything, but squatted down next to the kiln and circled around it several times.

He recalled the ancient glass history materials he had read in his previous life.

As early as ancient Egypt, artisans knew how to improve the quality of glass by heating it twice.

First, melt it at a high temperature, then let it cool down slightly and stand, allowing the bubbles to rise to the surface.

The key is to control the cooling rate, allowing the bubbles time to escape without causing the molten glass to solidify.

"Try again."

Ma Wenyuan stood up and dusted off his knees.

"Two changes: First, the quartz sand in the raw materials should be ground finer and sieved twice more."

"second……"

After a moment of silence, Ma Wenyuan said,

"After melting, don't rush to blow it. Lower the furnace temperature to 1200 degrees Celsius, keep it warm and let it stand for an hour, allowing the bubbles to rise on their own."

"Let it stand?" Fang Xiaoru frowned. "Won't the molten glass cool down?"

"No. At 1200 degrees Celsius, the glass is still liquid, just a little sticky."

"It's actually better if it's sticky, because the air bubbles will move slowly, but once they've escaped, they won't mix back in."

Ma Wenyuan patiently explained,

"This is called the clarification process. Pottery has its own intricacies, and glass has its own methods."

……

The second experiment proceeded entirely according to Ma Wenyuan's new plan.

The quartz sand was ground into powder and passed through a coarse sieve to a fine sieve three times.

After being placed in the furnace, the liquid is heated to 1400 degrees Celsius and maintained for two hours until it is completely melted.

Then remove some of the dampers to allow the furnace temperature to slowly drop to around 1200 degrees Celsius.

At this temperature, the molten glass becomes somewhat viscous, like malt syrup.

The melting chamber was extremely quiet. Occasionally, a bubble would rise to the surface of the liquid in the crucible, pop with a "pop," and then another one would appear.

An hour later, Ma Wenyuan signaled that it was time to start making the instrument.

He dipped the iron pipe in the liquid and skillfully blew out a glass bubble the size of a fist.

This time he was extra careful, blowing very slowly to ensure the glass wall was evenly stressed.

After molding, it was immediately sent into an annealing furnace and slowly cooled overnight.

……

Early the next morning.

Ma Wenyuan was awakened by Xu Miaoyun's screams.

Now the Marquis's mansion also has her bedroom, which, according to Xu Miaoyun, is to make it easier for her to study things and acquire knowledge.

After that, Xu Miaoyun rarely went home.

This allowed Xu Da to experience a bit of what it would be like for his own daughter to get married.

There's only one point: the two houses are too close to each other.

"Teacher! Teacher, please come out quickly!"

The nine-year-old girl shouted at the top of her lungs in the yard, her voice high-pitched and bright, startling the sparrows on the eaves into flight.

Ma Wenyuan put on an outer robe and ran out. The four students, including the Zhu brothers, were already gathered in front of the annealing kiln.

Xu Miaoyun held something in her hands, which were trembling slightly.

In the morning light, the glass slab was crystal clear.

There is no green.

Or rather, there is only a faint trace of green, which you have to stare at for a long time to notice.

The bubbles are almost invisible, the cup wall is smooth and clear, and when you look through the cup wall, the texture of the cotton cloth behind it is so clear that it looks like there is nothing in between.

"It's done."

Ma Wenyuan took the glass, looked at it against the sunlight, and said in a slightly tense voice, "It's done!"

Zeng Qing jumped up with a roar, almost knocking over the charcoal brazier next to him.

Xu Miaoyun was happy for a while, then suddenly quieted down, looked up at Ma Wenyuan,

"Teacher, can we use this glass to make a new telescope now?"

Ma Wenyuan paused for a moment, then burst into laughter: "You're only thinking about your telescope!"

"Of course!" Xu Miaoyun replied confidently.

"My old, shoddy body was so embarrassing. This time I'm going to make a real one, the kind where you can clearly see people's faces!"

Only now did Xu Miaoyun fully understand what her previous telescope actually was.

"OK."

It just hasn't really started yet.

Fang Xiaoru, however, had some doubts.

Xiao Fang, holding Xu Miaoyun's previously stolen goods, gradually frowned, finally looking at Xu Miaoyun.

"Miaoyun, what you said about 'convex lenses converging light rays' and 'concave lenses diverging light rays'..."

Fang Xiaoru was a scholar, and he did not feel ashamed to ask such questions.

Xu Miaoyun turned around and casually replied, "The teacher mentioned this."

Fang Xiaoru continued,

"I know, but I have a question: why do convex lenses converge? Why do concave lenses diverge? The teacher seems to have only given the conclusion, but not the underlying reason."

Xu Miaoyun blinked.

"Junior brother, what do you care about its origin? As long as it works, that's all that matters."

"No," Fang Xiaoru said seriously.

"To investigate things and acquire knowledge, one must thoroughly explore their principles. If one only knows what is but not why it is, then it is superficial learning."

He didn't dwell on the title.

It looked like the two were about to start arguing.

Ma Wenyuan then noticed them.

"Xiaoru asked a good question, and Miaoyun is also correct."

"Perfect timing! Since the telescope failed this time, I'll explain the principles of light from the beginning. Listen carefully."

Zhu Di and Zhu Su's eyes lit up; they had only seen Xu Miaoyun's notes before.

Just looking at notes can be incredibly enjoyable, so wouldn't it be even more fun to listen to lectures in person?

The six of them immediately sat down in unison.

Although Zeng Xiu and Xu Miaoyun felt they understood, they could only obediently prick up their ears when the teacher was going to explain.

Ma Wenyuan picked up a convex lens and a piece of white paper in his other hand, and walked into the sunlight.

He aimed the lens at the sun, adjusted the distance of the white paper, and soon a bright spot appeared on the paper, with a wisp of smoke rising from the scorched area.

"See that? A convex lens can focus sunlight into a single point. What's the principle behind that?"

Before anyone could answer, Ma Wenyuan continued,

"Light travels at different speeds in different media. When it enters glass from air, its speed slows down and its direction is deflected. This is called refraction."

"A convex lens is thicker in the middle and thinner at the edges. When light passes through it, the light rays on both sides are bent more sharply towards the middle, while the light rays in the middle are bent less, so they eventually converge."

"Conversely, a concave lens is thinner in the middle and thicker at the edges. When light passes through it, the light rays on both sides are deflected outwards, while those in the middle are not deflected much, so the light rays scatter."

Fang Xiaoru stared at the map on the ground, lost in thought.

He was a scholar, skilled in abstract thinking, but optics, which required geometric intuition, was still too new to him.

He pointed to the lines with arrows on the diagram and asked,

"Teacher, you said that light travels in a straight line and is deflected after passing through glass. How do you calculate the angle of deflection?"

"Good question."

Ma Wenyuan drew another diagram on the ground, marking the angle of incidence and the angle of refraction.

"This law is called the law of refraction. When light enters glass from air, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant."

"This constant depends on the properties of the two media. For our glass, this constant is approximately 1.5."

Fang Xiaoru murmured "ratio of sine" again, his brows furrowing even more.

He had heard of sine, a concept from mathematics.

But connecting sine waves with optics was completely beyond his comprehension.