Gu Nanjiao was so excited she almost jumped up. This...this really is saltpeter!

No wonder Bai Luochen appeared here. The Bai family of Yuzhou is indeed extraordinary; they can even find someone in such a godforsaken place.

This is saltpeter!

With martial prowess, he can wield fire to pacify the world; with literary skill, he can create ice to sweep away the entire city!

Whether it's making gunpowder or ice, they can make a fortune.

Thankfully she recognized it. It seems the older generation was right: if you master math, physics, and chemistry, you can go anywhere in the world without fear.

In the sweltering summer, a large bowl of ice is placed in the house, and a spoonful of icy watermelon is served with each bite. In ancient times, without air conditioning or fans, one could still enjoy the luxury of cooling off with ice!

Thinking about the refreshing and icy fruit juice, double-skin milk, and smoothies she would make, Gu Nanjiao couldn't help but drool. Just imagining the scene made her eager to try them.

Gu Nanjiao continued to use the hem of her skirt to scoop up some stones, not minding the dirt. Anyway, she had already scooped up mushrooms, so it didn't matter; she could wash them together later.

There wasn't much saltpeter exposed, and if she guessed correctly, there was likely a saltpeter mine underneath.

After returning home, Gu Nanjiao started looking for a basin. Most of the basins in the house were made of wood, which has poor thermal conductivity and is impossible to use for making ice. Fortunately, she had two copper pots, one large and one small, that she had used to make beef hot pot before, which were just right for making ice.

Fill two copper pots, one large and one small, with water, and then continuously add water to adjust the ratio. After many failed attempts, finally…

I successfully made a small pot of ice!

As the sun set, Lu's mother and younger sister returned.

When she saw the wisps of ice in the copper pot, Lu's mother asked in surprise, "Jiaojiao, where did you buy this ice?"

Ice was a rare commodity in ancient times, affordable only to high-ranking officials, wealthy gentry, and other affluent individuals. Even the richest families owned ice chests for chilling items or escaping the summer heat. In their small county towns, even if you had money, you might not be able to buy ice.

"Mother, this wasn't bought! I made it myself!" Gu Nanjiao said excitedly, pointing to the stone on the ground with her mother's hand, "I made it using this."

"These are just a few broken stones, how can they make ice?" Mother Lu was very puzzled.

"You'll see in a moment!" Gu Nan smiled mysteriously, took out two copper pots, one large and one small, and repeated the process as before.

Lu's mother and younger sister stared wide-eyed in shock.

Mother Lu said, "Jiaojiao, is it really that simple? You can make ice like this?" Good heavens, how lucky her son is! He actually married a treasure.

Gu Nanjiao smiled and said, "Yes, it's that simple."

"Sister-in-law, are you a fairy?" Lu Xiaomei couldn't help but ask.

Good heavens! That's incredible! Her sister-in-law can actually make ice cubes in the sweltering summer heat.

In Lu Xiaomei's heart, Gu Nanjiao's status suddenly rose to omnipotent, like a goddess.

Gu Nanjiao scratched her head a little embarrassedly: "Hey, it's nothing. I usually like to go to my dad's study to read. I just figured it out when I had nothing to do, just like your brother figured out how to brew wine while reading."

"However, ice made from saltpeter is not edible; it can be used to chill things or refrigerate meat dishes."

That evening, Lu Xiaomei ate Gu Nanjiao's chilled mung bean soup, feeling like she was in a dream.

What an idyllic life she lives! With her sister-in-law around, life is full of surprises and sweetness every day.

Gu Nanjiao specially cooked a large pot of mung beans, mashed them into mung bean paste, chilled it, and took it to her stall first thing tomorrow morning.

Because of the recent hot weather, Changyang Street is only bustling in the mornings, with only a few scattered people at other times. The business on the street depends entirely on the students of Nanxiang Academy.

As soon as Lu Yanzhao arrived, Gu Nanjiao handed him a cup of mung bean smoothie.

It was icy to the touch, and Lu Yanzhao was surprised to find that it had been chilled.

Nowadays, if people want to use ice in the summer, they need to freeze it in an ice cellar the following winter. But only wealthy families can afford ice cellars, so where would Gu Nanjiao get the ice?

"Iced?" Lu Yanzhao needed to verify.

"Hmm!" Gu Nanjiao propped her chin on one hand, blinked her big eyes at Lu Yanzhao, and made an interjection.

"Where did the ice come from?" Lu Yanzhao asked again.

Gu Nanjiao grew impatient: "Stop talking so much nonsense, hurry up and try it, how does it taste?"

Lu Yanzhao glanced at her, then stopped asking. He picked up a spoon and took a bite. It was soft and slightly grainy, sweet, and icy cold. On a hot summer day, it was incredibly refreshing.

"How about it?"

"Delicious!" Lu Yanzhao mumbled, not forgetting to tease her, "Where did you get this ice? You didn't just conjure it up out of thin air, did you?"

Hearing him say that, Gu Nanjiao's eyes widened in shock. She excitedly gave him a thumbs up and said, "You're so smart! You could even guess that. Let me tell you, I know magic, I can just conjure it up with a flick of my wrist."

Lu Yanzhao is petrified...

However, hearing Gu Nanjiao praise him for being smart made him feel sweet inside, even sweeter than eating mung bean shaved ice.

As more and more people gathered at the stall, Gu Nanjiao no longer had time to joke with Lu Yanzhao and quickly got busy.

The mung bean smoothie sold very well today, paired with spicy and delicious bullfrog—it was simply amazing.

After finishing his meal, Lu Yanzhao hurriedly returned to the academy. Before leaving, he didn't forget to ask Gu Nanjiao where she came from.

Gu Nanjiao told Lu Yanzhao everything about making ice with saltpeter.

Lu Yanzhao was shocked. What kind of treasure had he married? Could she really be a fox spirit who came to him, a scholar, to repay a debt from a past life and continue their predestined relationship?

It wasn't that Lu Yanzhao was superstitious; recently, Lin Ji had been telling Lu Yanzhao the story of a fox falling in love with a poor scholar and repaying his kindness with her own body. He had overheard a few of these stories and couldn't help but think of Gu Nanjiao.

Will she fall in love with him like the fox in the storybook?

...

After Lu Yanzhao left, Gu Nanjiao and the others calmly packed up.

Zheng Shiyi rushed over, flashing his signature big white teeth, and said with a smile, "Madam Gu, business is good!"

Gu Nanjiao quickly replied politely with a smile, "It's all thanks to Brother Zheng for helping me find this stall!" As she spoke, Gu Nanjiao handed a cup of mung bean smoothie to Zheng Shiyi, saying, "Brother, it's so hot in the summer, have a cup of mung bean smoothie to cool down!"

Zheng Shiyi was surprised to find that it was made of ice and asked curiously, "It's actually made of ice?"

"Yes."

Only the very wealthy could afford ice; small vendors outside would never spend a lot of money to buy ice to do business.

Zheng Shiyi was so curious that he couldn't help but ask, "Did you buy the ice with your own money?"

Gu Nanjiao nodded: "Yes!" She didn't want to spread the method of making ice with saltpeter to everyone, so as to avoid causing unnecessary trouble.

Zheng Shiyi could clearly tell that Gu Nanjiao didn't want to reveal too much, so he didn't ask any further questions.

He glanced at the stall in front of him and was surprised to find that his master did not have the braised pork offal he had been longing for.

"What about the pig offal? Is it all sold out?"