The method Yang Cheng came up with was the "summer ice making" technology used by ancient people on earth.
As the name suggests, "summer ice" refers to ice cubes made in summer, but in fact, the true meaning of "summer ice" is the technology of using hot water to make ice.
Some people may not understand that even in modern technologically advanced societies on earth, cold water must be placed in the refrigerator in advance to make ice cubes. In ancient times, hot water was used to make ice?
This does sound a bit incredible.
However, Yang Cheng remembered that he had indeed been on the Internet before, and in some ancient books he had seen, he could find many places recording the ancient methods of making "summer ice".
For example, the earliest record of "making ice in summer" is "Huainan Completion Technique" written by the Huainan School during the Western Han Dynasty. This was compiled under the leadership of Huainan King Liu An. The book says: "Put the boiling soup in an urn, and seal it with a new seal." , sinking into the well and turning into ice in three days.”
This means that by pouring boiled water into a large vat, sealing it, and then sinking it into the well water for three days and three nights, you can get ice cubes in the hot summer.
There is a process of gas adiabatic expansion and cooling, which can also be said to be the Joule-Thomson effect.
Boil the water in a small bottle until most of the air is removed from the bottle.
When the water in the bottle is about to boil and evaporate, immediately cover the mouth with fine silk fabric soaked in water, and immediately sink it into a deep well. The temperature in the bottle will drop sharply, which will cause water vapor to condense. In addition, the air pressure inside the bottle will drop sharply. It can be said to be approximately in a vacuum state, and then continue to be placed until the temperature of the bottle is similar to that of the outside world. In this way, a certain amount of ice can basically be produced.
The main principle is that after rapid evaporation of hot water under low pressure, it will absorb heat and quickly cool down. However, the condition is that all aspects must be well controlled. As long as the control is proper, ice making from hot water can still be achieved.
Although this method of "making ice in summer" is cumbersome, time-consuming and labor-intensive, and the ice produced is limited, in the Qingque Tribe, Yang Cheng has nothing to do now.
Before finding saltpeter, if you want to make ice to give everyone a little relief, you can only temporarily use this time-consuming and labor-intensive method.
"Since this method is to be used, it mainly solves two problems. One is that the container for hot water must be strong and sealed. The bottle cannot be broken because of a sudden change from hot to cold."
Yang Cheng touched his chin and thought, "Lulu has been studying porcelain recently. Making a sealed jar like this shouldn't be a big problem for her."
"As for sealing the mouth of the jar, this is actually simple. Just wrap it with a few layers of ramie cloth."
"The only issues that need to be considered are how large the container volume should be, how high the water temperature should be, and how to make ice cubes using this method. It seems to be related to air humidity. Air humidity affects the condensation of water vapor, and the air pressure inside the bottle decreases. .”
Yang Cheng thought about these problems for a long time, but there was no particularly good way to solve them.
We can only take one step at a time.
Yang Cheng first went to the kiln burning site to find Lulu. On a hot day, Lulu was sitting at the entrance of the kiln, looking at the fire inside. The firelight shone on her face, making her little face red. Small beads of sweat flowed from her face. The beads of sweat kept appearing on her forehead, so much so that she had to wipe them away every few seconds.
"Lulu."
"Wu, you're here."
"Well, come here quickly."
Yang Cheng pulled Lulu away from the kiln and pretended to scold: "Didn't I tell you? There are enough pottery in the tribe now. You don't need to bake any more. You don't have to sit in front of the pottery kiln every day. Burned."
"witch……"
Lulu felt aggrieved and sweet at the same time.
Yang Cheng said with a straight face: "Okay, you don't have to say anything, I'm angry and I want to punish you!"
"ah?"
Lulu was startled, then looked around nervously, her face suddenly turned red with embarrassment, and she grabbed the corner of her ramie clothes with her little hands: "Wu, are you here? It's not a good place here... I'm afraid of being seen... "
"What's wrong here? What are you afraid of being seen?" Yang Cheng looked confused.
"Okay! Wu, you punish me..." Lulu gritted her teeth, closed her eyes, leaned forward slightly, and raised her hips slightly.
"Meow meow meow?"
Yang Cheng's face became even more confused, and he wondered: "Lulu, what are you doing?"
Lulu's face was red with embarrassment, and she said in a voice as soft as a mosquito: "Wu... didn't you say you wanted to punish me... hurry up, if Yan Lin and the others see it, I will definitely die of shame..."
"..."
All right.
After hearing this and seeing Lulu's reaction, Yang Cheng finally figured out what was going on. He slapped his head and sighed: "Lulu, that's not what I meant."
Lulu looked up, her blushing face full of confusion. Yang Cheng could also understand the meaning in her eyes - "Wu, don't you usually like this tone?"
well--
Yang Cheng sighed again in his heart, blaming himself for being too unruly, which made Lulu think that the "punishment" Yang Cheng mentioned was the "punishment".
"Ahem."
Yang Cheng coughed and said, "Lulu, you misunderstood. The punishment I mentioned is to make you bake something for me."
"ah?"
Lulu was stunned for a moment, and then she realized what she was doing. She was immediately embarrassed and her face turned even redder.
After a while, he stamped his foot and said coquettishly: "Witch, you are so annoying, I will ignore you."
What should Yang Cheng do about this? He could only touch his nose, and then step forward and tell Lulu that when the ice comes out, Lulu would taste it second.
What, who is the first person to ask?
Of course that is the mighty, tall, handsome and wise Master Wu!
After coaxing Lulu nicely, the two of them started to do business. Well, real business, not that business.
"Witch, what kind of pottery do you want to make?" Lulu asked.
"Burn a few first, the size can be from small to large. The smallest one is as thick as an arm and two palms long; the largest one is as big as a bamboo knot like the bamboo we usually chop."
Yang Cheng said and gestured.
Yang Cheng had only read about the "Xia Zhibing" technology on the Internet, but had never actually practiced it. He didn't know what size of container would be appropriate.
So Lulu was given several choices. Even though the largest container was only as big as a bamboo joint, don't forget that the average bamboo in this world is one meter in diameter.
"But there is one requirement. Each container must be made with a thick body and a small mouth, and the position of the mouth should be smooth to make it easy to tie things on it."
Lulu nodded obediently, indicating that she understood.
