How did the ancients make ice?
Do you know? It is easy to make ice cubes now, as long as you have a refrigerator. But where did they get the ice cubes for summer in ancient times?
Storing ice
As early as the pre-Qin period, people used natural ice to keep food fresh and make cold drinks.
According to the "Book of Rites", in order to ensure the use of ice cubes in summer, the Zhou royal family set up a corresponding agency to manage the "ice policy", and the person in charge was called "Lingren".
The establishment of this department is not small, with a total of 80 "employees". Generally, from December every winter, workers begin to take natural ice cubes for storage.
How did the ancients store the ice in winter until summer and then use it when there were no refrigerators?
Answer: Ice
The conditions for storing ice in ancient times were certainly not as good as those of modern people, and the methods were relatively simple.
Every year during the Great Cold season, the ancients began to chisel ice for storage, because the ice cubes at this time were the hardest and not easy to melt. The officials who managed the storage of ice supervised slaves and farmers to chisel and collect in places with good water quality and store them in pre-prepared ice cellars.
Ice cellars are built in cool places, deep underground. Fresh straw and reed mats are used as mats. After putting ice on top, they are covered with insulation materials such as rice husks and leaves, and then the cellar mouth is sealed for use next year.
Because of this storage, about two-thirds of the stored ice will melt every year, so the ancients often increased the amount of ice stored to three times the amount of ice needed.
However, in the hot southern region,
the temperature is above zero all year round,
but it doesn't freeze, what should we do?
Ice making
Around the end of the Tang Dynasty, craftsmen mined a large amount of saltpeter when producing gunpowder. Occasionally, they found that saltpeter would absorb a lot of heat when dissolved in water, which could warm the surrounding water until it freezes.
So some skilled craftsmen began to use saltpeter to make ice.
The craftsmen put water in the jar, took a larger container, put water in the container, and then put the jar in the container, and continued to add saltpeter to the container, and the water in the jar froze into ice.
Saltpeter is a white, bitter crystal with a color like frost. The chemical name of saltpeter is calcium nitrate. When it is dissolved in water, it absorbs a lot of heat, lowering the surrounding temperature and forming ice.
After saltpeter is dissolved in water, it can be taken out and reused by cooling crystallization or evaporation crystallization. With this technology, the prosperity of the ancient refrigeration market has been greatly promoted.
Food is the first necessity of the people.
The prosperity of the refrigeration market will inevitably bring new breakthroughs in summer diet
Ice drinks
When it became possible to make ice cubes in summer, "ice fresh" also appeared in the market. The seafood caught by people was transported farther and preserved longer by freezing ice, and the living standards of the ancients were greatly improved.
Later, people began to put sugar and various fruits into the jars when making ice, gradually enriching the cold food products.
In the Song Dynasty, there were more varieties of cold food on the market. In the Southern Song Dynasty, drinks such as "snow-soaked bean water" and "snow-soaked plum wine" were sold in the streets in summer.
Although the ancient Western ice-making methods were not as efficient as modern technology, in the era when modern refrigeration equipment was lacking, people achieved the acquisition and preservation of ice through wisdom and natural conditions. The following are several major ancient Western ice-making methods:
1. Natural ice collection and storage (ice is collected in winter and used in summer)
Principle: In cold areas or in winter, people collect naturally formed ice directly from lakes and rivers.
Storage method:
Icehouse: In ancient Greece, ancient Rome and medieval Europe, people would dig underground icehouses (covered with insulating materials such as straw, wood or soil) to store ice collected in winter for use in summer.
Roman icehouse: The Romans would build icehouses in mountainous or cold areas, and even transport ice from the north to southern cities through trade.
Use: Used for refrigerating food, making cold drinks (such as chilled wine) or medical cooling
2. Saltpeter ice (chemical cooling)
Principle: When saltpeter (potassium nitrate) is dissolved in water, it absorbs a lot of heat, causing the surrounding temperature to drop sharply. This method was recorded in Europe in the 16th and 17th centuries for making small-scale ice or cooling drinks.
Application: European nobles may have used this method to make iced desserts or cold drinks, but it was expensive and not popular.
3. Other attempts
Alpine ice transport: Residents in areas such as the Alps would cut ice from high-altitude glaciers and transport it to cities.
Insulated containers: The ancient Greeks used double-layer metal cups (such as the prototype of the "thermos cup") to hold snow or ice to delay melting.
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