1 year ice storage overview China has a long history of ice storage, and written records began in the Western Zhou Dynasty. According to Zhou Li, at that time, in order to ensure the use of ice in summer, the Zhou royal family set up a corresponding organization to manage the "ice policy", which was called "bullying" by the person in charge. There are quite a few staff members in this institution, including "Ling Ren, Second Corporal, Second Officer, Second History, Eight Professions and Eighty Disciples".
In the Book of Songs in July, there is a poem describing ice harvesting: "In the second day, the ice cuts and rushes, and in the third day, it enters the Lingyin." The "Lingyin" here is the icehouse. According to the experience of the ancients, the igloo was built in a shady place with little wind. Generally, it is about 4 to 6 meters underground, or deeper. Every cold season, people begin to cut ice. First of all, we should investigate beforehand, find a place with good water quality and choose clean ice cubes without impurities. Then, the ice cubes should be stored in the ice room and paved with fresh straw and reed mats. After the ice is placed on it, it should be covered with rice bran, leaves and other heat insulation materials, and finally the pit is sealed.
Using this storage method, about two-thirds of the stored ice will melt in summer, so the ancients often increased the amount of stored ice to three times the amount needed.
▲ Ice guide, an ancient container for ice cubes.
The ice bank of the Zhou Dynasty was built underground. During the Three Kingdoms period, people began to build an ice bank on the ground and an ice well platform to store ice cubes.
In the Song Dynasty, there was a special official position in charge of ice storage in the palace. In the third year of Stegosaurus (962), an ice well department was set up in Zhao Kuangyin in the early Song Dynasty, which belonged to the Imperial City Division.
In the Qing dynasty, ice was stored on a large scale. According to Qingyi, there are five pits in the Forbidden City, with a maximum ice storage capacity of 25,000. There are 6 pits in the west gate of Jingshan, with an ice storage scale of 54,000 pieces; There are 3 pits outside Deshengmen, with an ice storage capacity of 26,700.
▲ Icehouse in the Forbidden City
2 Overview of saltpetre ice making Ancient Taoist priests found that saltpetre can cool down when put into water, enough to freeze water. Because the main component of saltpeter is potassium nitrate, potassium nitrate will absorb a lot of heat after dissolving in water. At the end of the Tang Dynasty, some people used saltpeter to make ice.
This way of making ice is not limited by seasons. Moreover, after saltpetre is dissolved in water, saltpetre can be extracted by cooling crystallization or evaporation crystallization for reuse. The adoption of this technology greatly promoted the development of ancient refrigeration industry.
▲ Nitrite for ice making.
With ice, people in the palace can not only use ice to cool down, but also use ice to keep food fresh, make all kinds of cold drinks and improve their living standards.